The efficiency of photocatalytic overall water splitting was mainly limited by the slow reaction kinetics of water oxidation.How to design effective surface active site to overcome the slow water oxidation reaction wa...The efficiency of photocatalytic overall water splitting was mainly limited by the slow reaction kinetics of water oxidation.How to design effective surface active site to overcome the slow water oxidation reaction was a major challenge.Here,we propose a strategy to accelerate surface water oxidation through the fabrication spatially separated double active sites.FeCoPi/Bi_(4)NbO_(8)Cl-OVs photocatalyst with spatially separated double active site was prepared by hydrogen reduction photoanode deposition method.Due to the high matching of the spatial loading positions of FeCoPi and OVs with the photogenerated charge distribution of Bi_(4)NbO_(8)Cl and corresponding reaction mechanisms of substrate,the FeCoPi and OVs on the(001)and(010)crystal planes of Bi_(4)NbO_(8)Cl photocatalyst provided surface active site for water oxidation reaction and electron shuttle reaction(Fe^(3+)/Fe^(2+)),respectively.Under visible light irradiation,the evolution O_(2)rate of FeCoPi/Bi_(4)NbO_(8)Cl OVs was 16.8μmol h^(-1),as 32.9 times as Bi_(4)NbO_(8)Cl.Furthermore,a hydrogen evolution co-catalyst PtRu@Cr_(2)O_(3)was prepared by sequential photodeposition method.Due to the introduction of Ru,the Schottky barrier between PbTiO_(3)and Pt was effectively reduced,which promoted the transfer of photogenerated electrons to PtRu@Cr_(2)O_(3)thermodynamically,the evolution H_(2)rate on PtRu@Cr_(2)O_(3)/PbTiO_(3)increased to 664.8 times.On based of the synchronous enhancement of the water oxidation performance on FeCoPi/Bi_(4)NbO_(8)Cl-OVs and water reduction performance on PtRu@Cr_(2)O_(3)/PbTiO_(3),a novel Z-Scheme photocatalytic overall water splitting system(FeCoPi/Bi_(4)NbO_(8)Cl-OVs)mediated by Fe^(3+)/Fe^(2+)had successfully constructed.Under visible light irradiation,the evolution rates of H_(2)and O_(2)were 2.5 and 1.3μmol h^(-1),respectively.This work can provide some reference for the design of active site and the controllable synthesis of OVs spatial position.On the other hand,the hydrogen evolution co catalyst(PtRu@Cr_(2)O_(3))and the co catalyst FeCoPi for oxygen evolution contributed to the construction of an overall water splitting system.展开更多
The active sites of samarium orthovanadate(SmVO 4) were studied by means of ESR, NO TPD and temperature programmed 18 O 2 isotope exchange(TPIE) methods. The results of ESR and NO TPD confirm the presenc...The active sites of samarium orthovanadate(SmVO 4) were studied by means of ESR, NO TPD and temperature programmed 18 O 2 isotope exchange(TPIE) methods. The results of ESR and NO TPD confirm the presence of V 4+ in the catalyst. The TPIE revealed that the 18 O 2 isotope exchange was carried out through a single exchange procedure. The V 4+ species associated with oxygen vacancies are the sites for O 2 activation.展开更多
Durable and inexpensive graphitic carbon nitride(g-C_(3)N_(4))demonstrates great potential for achieving efficient photocatalytic hydrogen evolution reduction(HER).To further improve its activity,g-C_(3)N_(4)was subje...Durable and inexpensive graphitic carbon nitride(g-C_(3)N_(4))demonstrates great potential for achieving efficient photocatalytic hydrogen evolution reduction(HER).To further improve its activity,g-C_(3)N_(4)was subjected to atomic-level structural engineering by doping with transition metals(M=Fe,Co,or Ni),which simultaneously induced the formation of metal-N active sites in the g-C_(3)N_(4)framework and modulated the bandgap of g-C_(3)N_(4).Experiments and density functional theory calculations further verified that the as-formed metal-N bonds in M-doped g-C_(3)N_(4)acted as an"electron transfer bridge",where the migration of photo-generated electrons along the bridge enhanced the efficiency of separation of the photogenerated charges,and the optimized bandgap of g-C_(3)N_(4)afforded stronger reduction ability and wider light absorption.As a result,doping with either Fe,Co,or Ni had a positive effect on the HER activity,where Co-doped g-C_(3)N_(4)exhibited the highest performance.The findings illustrate that this atomic-level structural engineering could efficiently improve the HER activity and inspire the design of powerful photocatalysts.展开更多
Heterogeneous catalysts with ultra-small clusters and atomically dispersed(USCAD)active sites have gained increasing attention in recent years.However,developing USCAD catalysts with high-density metal sites anchored ...Heterogeneous catalysts with ultra-small clusters and atomically dispersed(USCAD)active sites have gained increasing attention in recent years.However,developing USCAD catalysts with high-density metal sites anchored in porous nanomaterials is still challenging.Here,through the template-free S-assisted pyrolysis of low-cost Fe-salts with melamine(MA),porous alveolate Fe/g-C3N4 catalysts with high-density(Fe loading up to 17.7 wt%)and increased USCAD Fe sites were synthesized.The presence of a certain amount of S species in the Fe-salts/MA system plays an important role in the formation of USCAD S-Fe-salt/CN catalysts;the S species act as a"sacrificial carrier"to increase the dispersion of Fe species through Fe-S coordination and generate porous alveolate structure by escaping in the form of SO2 during pyrolysis.The S-Fe-salt/CN catalysts exhibit greatly promoted activity and reusability for degrading various organic pollutants in advanced oxidation processes compared to the corresponding Fe-salt/CN catalysts,due to the promoted accessibility of USCAD Fe sites by the porous alveolate structure.This S-assisted method exhibits good feasibility in a large variety of S species(thiourea,S powder,and NH4SCN)and Fe salts,providing a new avenue for the low-cost and large-scale synthesis of high-density USCAD metal/g-C3N4 catalysts.展开更多
Photocatalytic hydrogen evolution is an attractive fi eld for future environment-friendly energy.However,fast recombination of photogenerated charges severely inhibits hydrogen effi ciency.Single-atom cocatalysts such...Photocatalytic hydrogen evolution is an attractive fi eld for future environment-friendly energy.However,fast recombination of photogenerated charges severely inhibits hydrogen effi ciency.Single-atom cocatalysts such as Pt have emerged as an eff ective method to enhance the photocatalytic activity by introduction of active sites and boosting charge separation with low-coordination environment.Herein,we demonstrated a new strategy to develop a highly active Pd single atom in carbondefi cient g-C_(3)N_(4)with a unique coordination.The single-atom Pd–N_(3)sites constructed by oil bath heating and photoreduction process were confi rmed by HADDF-STEM and XPS measurements.Introduction of single-atom Pd greatly improved the separation and transportation of charge carriers,leading to a longer lifespan for consequent reactions.The obtained singleatom Pd loaded on the carbon-defi cient g-C_(3)N_(4)showed excellent photocatalytic activity in hydrogen production with about 24 and 4 times higher activity than that of g-C_(3)N_(4)and nano-sized Pd on the same support,respectively.This work provides a new insight on the design of single-atom catalyst.展开更多
CO oxidation has been performed on Co_(3)O_(4) nanobelts and nanocubes as model catalysts.The Co_(3)O_(4) nanobelts which have a predominance of exposed{011}planes are more active than Co_(3)O_(4) nanocubes with expos...CO oxidation has been performed on Co_(3)O_(4) nanobelts and nanocubes as model catalysts.The Co_(3)O_(4) nanobelts which have a predominance of exposed{011}planes are more active than Co_(3)O_(4) nanocubes with exposed{001}planes.Temperature programmed reduction of CO shows that Co_(3)O_(4) nanobelts have stronger reducing properties than Co_(3)O_(4) nanocubes.The essence of shape and crystal plane effect is revealed by the fact that turnover frequency of Co3+sites of{011}planes on Co_(3)O_(4) nanobelts is far higher than that of{001}planes on Co_(3)O_(4) nanocubes.展开更多
Designing bifunctional oxygen electrocatalysts with high activity,lasting stability,and low-cost for rechargeable zinc-air batteries(RZABs)is a tough challenge.Herein,an advanced electrocatalyst is prepared by anchori...Designing bifunctional oxygen electrocatalysts with high activity,lasting stability,and low-cost for rechargeable zinc-air batteries(RZABs)is a tough challenge.Herein,an advanced electrocatalyst is prepared by anchoring atomically dispersed Co atoms on Ndoped graphene-like hierarchically porous carbon nanosheets(SA-Co-N4-GCs)and thereby forming Co-N4-C architecture.Its unique structure with excellent conductivity,large surface area,and three dimensional(3D)interconnected hierarchically porous architecture exposes not only more Co-N4 active sites to accelerate the kinetics of both oxygen reduction reaction(ORR)and oxygen evolution reaction(OER),but also provides an efficient charge/mass transport environment to reduce diffusion barrier.Consequently,SA-Co-N4-GCs exhibits excellent ORR/OER bifunctional activities and durability,surpassing noble-metal catalysts.Liquid RZABs using SA-Co-N4-GCs cathodes display a high open-circuit voltage of 1.51 V,a remarkable power density of 149.3 mW·cm−2,as well as excellent stability and rechargeability with faint increase in polarization even at a large depth of charge–discharge cycle with 16 h per cycle over an entire 600 h long-term test.Moreover,flexible quasi-solid-state RZABs with SA-Co-N4-GCs cathodes also deliver a considerable power density of 124.5 mW·cm−2,which is even higher than that of liquid batteries using noble-metal catalysts.This work has thrown new insight into development of high-performance and low-cost electrocatalysts for energy conversion and storage.展开更多
Developing efficient transition metal-nitrogen-carbon(TM-N-C)catalysts with abundant accessible active sites has been in the limelight in recent years due to their exceptional application potential in Zn-air bat-terie...Developing efficient transition metal-nitrogen-carbon(TM-N-C)catalysts with abundant accessible active sites has been in the limelight in recent years due to their exceptional application potential in Zn-air bat-teries(ZABs).Herein,we report the simple and environmentally-friendly fabrication of a single-atom Co electrocatalyst,Co-SA/N-C_(900),via in-suit pyrolysis of the co-precursor containing sucrose,dicyandiamide,and Co salts.The Co single atoms coordinated with adjacent N atoms are anchored on the doped ordered mesoporous carbon,generating the atomic Co-N_(4)moiety.Co-SA/N-C_(900)displays high oxygen reduction reaction(ORR)activity with an onset potential of 0.96 V and a half-wave potential of 0.87 V.Notably,the liquid ZAB with Co-SA/N-C_(900)catalyst exhibits exceptional discharge specific capacity of 706.38 mAh g^(-1),peak power density of 191.11 mW cm^(-2),and excellent stability at high current densities up to 100 mA cm^(-2),surpassing commercial Pt/C.According to the density functional theory(DFT)study,the Co-N_(4)moi-ety with graphitic N dopants can decrease the rate-determining step(RDS)energy barrier and thus accel-erate the ORR process.This study offers experimental and theoretical guidelines for the rational design of TM-N-C catalysts for practical implementation with notable ORR activity for application in ZABs.展开更多
Controllable design and synthesis of catalysts with the target active sites are extremely important for their applications such as for the oxygen reduction reaction(ORR)in fuel cells.However,the controllably synthesiz...Controllable design and synthesis of catalysts with the target active sites are extremely important for their applications such as for the oxygen reduction reaction(ORR)in fuel cells.However,the controllably synthesizing electrocatalysts with a single type of active site still remains a grand challenge.In this study,we developed a facile and scalable method for fabricating highly efficient ORR electrocatalysts with sole atomic Fe-N4 species as the active site.Herein,the use of cost-effective highly porous carbon as the support not only could avoid the aggregation of the atomic Fe species but also a feasible approach to reduce the catalyst cost.The obtained atomic Fe-N4 in activated carbon(aFe@AC)shows excellent ORR activity.Its half-wave potential is 59 mV more negative but 47 mV more positive than that of the commercial Pt/C in acidic and alkaline electrolytes,respectively.The full cell performance test results show that the aFe@AC sample is a promising candidate for direct methanol fuel cells.This study provides a general method to prepare catalysts with a certain type of active site and definite numbers.展开更多
Silver‐modified semiconductor photocatalysts typically exhibit enhanced photocatalytic activitytoward the degradation of organic substances.In comparison,their hydrogen‐evolution rates arerelatively low owing to poo...Silver‐modified semiconductor photocatalysts typically exhibit enhanced photocatalytic activitytoward the degradation of organic substances.In comparison,their hydrogen‐evolution rates arerelatively low owing to poor interfacial catalytic reactions to producing hydrogen.In the presentstudy,thiocyanate anions(SCN–)as interfacial catalytic active sites were selectively adsorbed ontothe Ag surface of g‐C3N4/Ag photocatalyst to promote interfacial H2‐evolution reactions.The thiocyanate‐modified g‐C3N4/Ag(g‐C3N4/Ag‐SCN)photocatalysts were synthesized via photodepositionof metallic Ag on g‐C3N4and subsequent selective adsorption of SCN– ions on the Ag surface by animpregnation method.The resulting g‐C3N4/Ag‐SCN photocatalysts exhibited considerably higherphotocatalytic H2‐evolution activity than the g‐C3N4,g‐C3N4/Ag,and g‐C3N4/SCN photocatalysts.Furthermore,the g‐C3N4/Ag‐SCN photocatalyst displayed the highest H2‐evolution rate(3.9μmolh?1)when the concentration of the SCN– ions was adjusted to0.3mmol L?1.The H2‐evolution rateobtained was higher than those of g‐C3N4(0.15μmol h?1)and g‐C3N4/Ag(0.71μmol h?1).Consideringthe enhanced performance of g‐C3N4/Ag upon minimal addition of SCN– ions,a synergistic effectof metallic Ag and SCN– ions is proposed―the Ag nanoparticles act as an effective electron‐transfermediator for the steady capture and rapid transportation of photogenerated electrons,while theadsorbed SCN– ions serve as an interfacial active site to effectively absorb protons from solution andpromote rapid interfacial H2‐evolution reactions.Considering the present facile synthesis and itshigh efficacy,the present work may provide new insights into preparing high‐performance photocatalytic materials展开更多
Piezocatalytic activation of persulfate(PS) has great application potential in environmental remediation;however,the relationship between piezocatalyst thickness and catalytic activity is not clear,limiting the furthe...Piezocatalytic activation of persulfate(PS) has great application potential in environmental remediation;however,the relationship between piezocatalyst thickness and catalytic activity is not clear,limiting the further improvement of catalytic activity and application of the technology.Herein,the Bi_(2)Fe_(4)O_(9)(BFO) piezocatalysts with tunable thickness were prepared through a facile hydrothermal method by tuning the molar ratio of Bi(NO_(3)),5H_(2)O and FeCl_(3)·6H_(2)O for piezocatalytic activation of peroxydisulfate(PDS).The BFO with the smallest thickness exhibits excellent catalytic activity,and the SO_(4)^(·-)and ·OH are the major reactive oxygen species for degrading organic pollutants.Further XPS investigations and finite element analyses demonstrate that the decreased thickness of BFO not only exposes more Fe^(2+)sites for PDS activation,but also improve the piezoelectric effect to accelerate the regeneration of Fe^(2+),thus enabling an enhanced synergy effect between PDS activation and piezocatalysis for outstanding catalytic activity.This work provides an understanding of the relationship between thickness of piezocatalysts and its catalytic activity over PDS activation,facilitating the development of more efficient piezocatalysts and PS-based advanced oxidation processes.展开更多
The development of an active, durable, and metal-free carbocatalyst that is able to replace metal-based catalysts is of increasing scientific and technological importance. The use of such a catalyst would avoid proble...The development of an active, durable, and metal-free carbocatalyst that is able to replace metal-based catalysts is of increasing scientific and technological importance. The use of such a catalyst would avoid problems caused by metal- containing catalysts, for example, environmental pollution by heavy metals and depletion of rare metal resources. Herein, an active and durable graphene carbocatalyst is presented for the carbocatalytic conversion of 4-nitrophenol to 4-aminophenol at ambient temperature. The carbocatalyst was prepared via a mild, water-based reaction between L-ascorbic acid （AA） and graphene oxide （GO） and did not involve any other reactants. During the structure and catalytic property optimization, a series of carbocatalysts were fabricated at various reaction temperatures and AA/GO ratios. Using several characterization techniques, detailed structural features of these carbocatalysts were identified. Possible active species and sites on the carbocatalysts were also identified such as certain oxygen-containing groups, the ~x-conjugated system, and graphene sheet edges. In addition, the synergistic effect between these active species and sites on the resulting catalytic activity is highlighted. Furthermore, we clarified the origin of the high stability and durability of the optimized carbocatalyst. The work presented here aids the design of high-performance carbocatalysts for hydrogenation reactions, and increases understanding of the structural and mechanistic aspects at the molecular level that lead to high catalyst activity and durability.展开更多
Na_(3)V_(2)(PO_(4))_(3)(NVP),as a great potential cathode candidate for Na-ion batteries(NIBs),has attracted enormous interest due to its three-dimensional(3D)large open framework for convenient Na+transport,yet its p...Na_(3)V_(2)(PO_(4))_(3)(NVP),as a great potential cathode candidate for Na-ion batteries(NIBs),has attracted enormous interest due to its three-dimensional(3D)large open framework for convenient Na+transport,yet its practical application is still limited by its inferior electron conductivity and sluggish Na+diffusion kinetics.Herein,the tiny Cr doped hierarchical NVP micro-flower cathodes(i.e.,Na_(3)V_(2-x)Crx(PO_(4))_(3)@C,x≤0.1),which are self-assembled with single-crystal nanoflake subunits in-situ coated with carbon nano-shell,are designed and fabricated via a scalable avenue.The optimized cathode,i.e.,Na_(3)V_(1.94)Cr_(0.06)(PO_(4))_(3)@C(NVCP-6),was endowed with more electro-active Na(2)sites and higher electronic/ionic conductivity for efficient sodium storage.Benefiting from these competitive merits,the NVCP-6,when evaluated as a cathode towards NIBs,exhibits an ultrahigh-rate capability of 99.8 mAh·g^(-1)at 200 C and superior stability of 82.2%over 7300 cycles at 50 C.Furthermore,the NVCP-6 based full NIBs display remarkable electrochemical properties in terms of both high-rate capacities and long-duration cycling properties at different temperatures(-20–50°C).The contribution,i.e.,the design of“four ounces can move a thousand pounds”,here will promote the practical industrial application of NVP towards advanced NIBs.展开更多
基金supported by National Natural Science Foundation of China(22369022)Technology Innovation Leading Program of Shaanxi(2022QFY07-03)。
文摘The efficiency of photocatalytic overall water splitting was mainly limited by the slow reaction kinetics of water oxidation.How to design effective surface active site to overcome the slow water oxidation reaction was a major challenge.Here,we propose a strategy to accelerate surface water oxidation through the fabrication spatially separated double active sites.FeCoPi/Bi_(4)NbO_(8)Cl-OVs photocatalyst with spatially separated double active site was prepared by hydrogen reduction photoanode deposition method.Due to the high matching of the spatial loading positions of FeCoPi and OVs with the photogenerated charge distribution of Bi_(4)NbO_(8)Cl and corresponding reaction mechanisms of substrate,the FeCoPi and OVs on the(001)and(010)crystal planes of Bi_(4)NbO_(8)Cl photocatalyst provided surface active site for water oxidation reaction and electron shuttle reaction(Fe^(3+)/Fe^(2+)),respectively.Under visible light irradiation,the evolution O_(2)rate of FeCoPi/Bi_(4)NbO_(8)Cl OVs was 16.8μmol h^(-1),as 32.9 times as Bi_(4)NbO_(8)Cl.Furthermore,a hydrogen evolution co-catalyst PtRu@Cr_(2)O_(3)was prepared by sequential photodeposition method.Due to the introduction of Ru,the Schottky barrier between PbTiO_(3)and Pt was effectively reduced,which promoted the transfer of photogenerated electrons to PtRu@Cr_(2)O_(3)thermodynamically,the evolution H_(2)rate on PtRu@Cr_(2)O_(3)/PbTiO_(3)increased to 664.8 times.On based of the synchronous enhancement of the water oxidation performance on FeCoPi/Bi_(4)NbO_(8)Cl-OVs and water reduction performance on PtRu@Cr_(2)O_(3)/PbTiO_(3),a novel Z-Scheme photocatalytic overall water splitting system(FeCoPi/Bi_(4)NbO_(8)Cl-OVs)mediated by Fe^(3+)/Fe^(2+)had successfully constructed.Under visible light irradiation,the evolution rates of H_(2)and O_(2)were 2.5 and 1.3μmol h^(-1),respectively.This work can provide some reference for the design of active site and the controllable synthesis of OVs spatial position.On the other hand,the hydrogen evolution co catalyst(PtRu@Cr_(2)O_(3))and the co catalyst FeCoPi for oxygen evolution contributed to the construction of an overall water splitting system.
文摘The active sites of samarium orthovanadate(SmVO 4) were studied by means of ESR, NO TPD and temperature programmed 18 O 2 isotope exchange(TPIE) methods. The results of ESR and NO TPD confirm the presence of V 4+ in the catalyst. The TPIE revealed that the 18 O 2 isotope exchange was carried out through a single exchange procedure. The V 4+ species associated with oxygen vacancies are the sites for O 2 activation.
文摘Durable and inexpensive graphitic carbon nitride(g-C_(3)N_(4))demonstrates great potential for achieving efficient photocatalytic hydrogen evolution reduction(HER).To further improve its activity,g-C_(3)N_(4)was subjected to atomic-level structural engineering by doping with transition metals(M=Fe,Co,or Ni),which simultaneously induced the formation of metal-N active sites in the g-C_(3)N_(4)framework and modulated the bandgap of g-C_(3)N_(4).Experiments and density functional theory calculations further verified that the as-formed metal-N bonds in M-doped g-C_(3)N_(4)acted as an"electron transfer bridge",where the migration of photo-generated electrons along the bridge enhanced the efficiency of separation of the photogenerated charges,and the optimized bandgap of g-C_(3)N_(4)afforded stronger reduction ability and wider light absorption.As a result,doping with either Fe,Co,or Ni had a positive effect on the HER activity,where Co-doped g-C_(3)N_(4)exhibited the highest performance.The findings illustrate that this atomic-level structural engineering could efficiently improve the HER activity and inspire the design of powerful photocatalysts.
文摘Heterogeneous catalysts with ultra-small clusters and atomically dispersed(USCAD)active sites have gained increasing attention in recent years.However,developing USCAD catalysts with high-density metal sites anchored in porous nanomaterials is still challenging.Here,through the template-free S-assisted pyrolysis of low-cost Fe-salts with melamine(MA),porous alveolate Fe/g-C3N4 catalysts with high-density(Fe loading up to 17.7 wt%)and increased USCAD Fe sites were synthesized.The presence of a certain amount of S species in the Fe-salts/MA system plays an important role in the formation of USCAD S-Fe-salt/CN catalysts;the S species act as a"sacrificial carrier"to increase the dispersion of Fe species through Fe-S coordination and generate porous alveolate structure by escaping in the form of SO2 during pyrolysis.The S-Fe-salt/CN catalysts exhibit greatly promoted activity and reusability for degrading various organic pollutants in advanced oxidation processes compared to the corresponding Fe-salt/CN catalysts,due to the promoted accessibility of USCAD Fe sites by the porous alveolate structure.This S-assisted method exhibits good feasibility in a large variety of S species(thiourea,S powder,and NH4SCN)and Fe salts,providing a new avenue for the low-cost and large-scale synthesis of high-density USCAD metal/g-C3N4 catalysts.
基金This work was supported by the National Natural Science Foundation of China(Nos.21976116,21473248)Guangdong Science and Technology Program(No.2018A050506025)+3 种基金Guangzhou Science and Technology Program(Nos.202002030406,201804010181)High Level Talents Introduction Project of"Pearl River Talent Plan"in Guangdong Province(No.2019CX01L308)the Support Scheme of Guangzhou for Leading Talents in Innovation and Entrepreneurship Funding(No.2016015)the Key Deployment Projects of Chinese Academy of Sciences(No.ZDRW_CN_2020_1).
文摘Photocatalytic hydrogen evolution is an attractive fi eld for future environment-friendly energy.However,fast recombination of photogenerated charges severely inhibits hydrogen effi ciency.Single-atom cocatalysts such as Pt have emerged as an eff ective method to enhance the photocatalytic activity by introduction of active sites and boosting charge separation with low-coordination environment.Herein,we demonstrated a new strategy to develop a highly active Pd single atom in carbondefi cient g-C_(3)N_(4)with a unique coordination.The single-atom Pd–N_(3)sites constructed by oil bath heating and photoreduction process were confi rmed by HADDF-STEM and XPS measurements.Introduction of single-atom Pd greatly improved the separation and transportation of charge carriers,leading to a longer lifespan for consequent reactions.The obtained singleatom Pd loaded on the carbon-defi cient g-C_(3)N_(4)showed excellent photocatalytic activity in hydrogen production with about 24 and 4 times higher activity than that of g-C_(3)N_(4)and nano-sized Pd on the same support,respectively.This work provides a new insight on the design of single-atom catalyst.
基金This work was supported by National Natural Science Foundation of China(NSFC)(Nos.10979031,20921001,and 90606006)the“973”State Key Project(No.2006CB932303)and the China Postdoctoral Science Foundation(No.20080440361).
文摘CO oxidation has been performed on Co_(3)O_(4) nanobelts and nanocubes as model catalysts.The Co_(3)O_(4) nanobelts which have a predominance of exposed{011}planes are more active than Co_(3)O_(4) nanocubes with exposed{001}planes.Temperature programmed reduction of CO shows that Co_(3)O_(4) nanobelts have stronger reducing properties than Co_(3)O_(4) nanocubes.The essence of shape and crystal plane effect is revealed by the fact that turnover frequency of Co3+sites of{011}planes on Co_(3)O_(4) nanobelts is far higher than that of{001}planes on Co_(3)O_(4) nanocubes.
基金the National Natural Science Foundation of China(Nos.21603103 and U1601214)the Natural Science Foundation Committee of Jiangsu Province(No.BK20171462)the Postgraduate Research&Practice Innovation Program of Jiangsu Province(No.SJCX21_0465).
文摘Designing bifunctional oxygen electrocatalysts with high activity,lasting stability,and low-cost for rechargeable zinc-air batteries(RZABs)is a tough challenge.Herein,an advanced electrocatalyst is prepared by anchoring atomically dispersed Co atoms on Ndoped graphene-like hierarchically porous carbon nanosheets(SA-Co-N4-GCs)and thereby forming Co-N4-C architecture.Its unique structure with excellent conductivity,large surface area,and three dimensional(3D)interconnected hierarchically porous architecture exposes not only more Co-N4 active sites to accelerate the kinetics of both oxygen reduction reaction(ORR)and oxygen evolution reaction(OER),but also provides an efficient charge/mass transport environment to reduce diffusion barrier.Consequently,SA-Co-N4-GCs exhibits excellent ORR/OER bifunctional activities and durability,surpassing noble-metal catalysts.Liquid RZABs using SA-Co-N4-GCs cathodes display a high open-circuit voltage of 1.51 V,a remarkable power density of 149.3 mW·cm−2,as well as excellent stability and rechargeability with faint increase in polarization even at a large depth of charge–discharge cycle with 16 h per cycle over an entire 600 h long-term test.Moreover,flexible quasi-solid-state RZABs with SA-Co-N4-GCs cathodes also deliver a considerable power density of 124.5 mW·cm−2,which is even higher than that of liquid batteries using noble-metal catalysts.This work has thrown new insight into development of high-performance and low-cost electrocatalysts for energy conversion and storage.
基金This work was financially supported by the National Natural Science Foundation of China(Nos.22078028 and 21978026).
文摘Developing efficient transition metal-nitrogen-carbon(TM-N-C)catalysts with abundant accessible active sites has been in the limelight in recent years due to their exceptional application potential in Zn-air bat-teries(ZABs).Herein,we report the simple and environmentally-friendly fabrication of a single-atom Co electrocatalyst,Co-SA/N-C_(900),via in-suit pyrolysis of the co-precursor containing sucrose,dicyandiamide,and Co salts.The Co single atoms coordinated with adjacent N atoms are anchored on the doped ordered mesoporous carbon,generating the atomic Co-N_(4)moiety.Co-SA/N-C_(900)displays high oxygen reduction reaction(ORR)activity with an onset potential of 0.96 V and a half-wave potential of 0.87 V.Notably,the liquid ZAB with Co-SA/N-C_(900)catalyst exhibits exceptional discharge specific capacity of 706.38 mAh g^(-1),peak power density of 191.11 mW cm^(-2),and excellent stability at high current densities up to 100 mA cm^(-2),surpassing commercial Pt/C.According to the density functional theory(DFT)study,the Co-N_(4)moi-ety with graphitic N dopants can decrease the rate-determining step(RDS)energy barrier and thus accel-erate the ORR process.This study offers experimental and theoretical guidelines for the rational design of TM-N-C catalysts for practical implementation with notable ORR activity for application in ZABs.
基金The authors would like to thank the Australian Research Council(ARC DP170103317,DP200103043)for financial support during the course of this study.Prof Jun Chen would like to thank the Australian National Fabrication Facility and EMC at the University of Wollongong for facilities/equipment access.
文摘Controllable design and synthesis of catalysts with the target active sites are extremely important for their applications such as for the oxygen reduction reaction(ORR)in fuel cells.However,the controllably synthesizing electrocatalysts with a single type of active site still remains a grand challenge.In this study,we developed a facile and scalable method for fabricating highly efficient ORR electrocatalysts with sole atomic Fe-N4 species as the active site.Herein,the use of cost-effective highly porous carbon as the support not only could avoid the aggregation of the atomic Fe species but also a feasible approach to reduce the catalyst cost.The obtained atomic Fe-N4 in activated carbon(aFe@AC)shows excellent ORR activity.Its half-wave potential is 59 mV more negative but 47 mV more positive than that of the commercial Pt/C in acidic and alkaline electrolytes,respectively.The full cell performance test results show that the aFe@AC sample is a promising candidate for direct methanol fuel cells.This study provides a general method to prepare catalysts with a certain type of active site and definite numbers.
基金supported by the National Natural Science Foundation of China(51472192,21477094,21771142)the Fundamental Research Funds for the Central Universities(WUT 2017IB002)~~
文摘Silver‐modified semiconductor photocatalysts typically exhibit enhanced photocatalytic activitytoward the degradation of organic substances.In comparison,their hydrogen‐evolution rates arerelatively low owing to poor interfacial catalytic reactions to producing hydrogen.In the presentstudy,thiocyanate anions(SCN–)as interfacial catalytic active sites were selectively adsorbed ontothe Ag surface of g‐C3N4/Ag photocatalyst to promote interfacial H2‐evolution reactions.The thiocyanate‐modified g‐C3N4/Ag(g‐C3N4/Ag‐SCN)photocatalysts were synthesized via photodepositionof metallic Ag on g‐C3N4and subsequent selective adsorption of SCN– ions on the Ag surface by animpregnation method.The resulting g‐C3N4/Ag‐SCN photocatalysts exhibited considerably higherphotocatalytic H2‐evolution activity than the g‐C3N4,g‐C3N4/Ag,and g‐C3N4/SCN photocatalysts.Furthermore,the g‐C3N4/Ag‐SCN photocatalyst displayed the highest H2‐evolution rate(3.9μmolh?1)when the concentration of the SCN– ions was adjusted to0.3mmol L?1.The H2‐evolution rateobtained was higher than those of g‐C3N4(0.15μmol h?1)and g‐C3N4/Ag(0.71μmol h?1).Consideringthe enhanced performance of g‐C3N4/Ag upon minimal addition of SCN– ions,a synergistic effectof metallic Ag and SCN– ions is proposed―the Ag nanoparticles act as an effective electron‐transfermediator for the steady capture and rapid transportation of photogenerated electrons,while theadsorbed SCN– ions serve as an interfacial active site to effectively absorb protons from solution andpromote rapid interfacial H2‐evolution reactions.Considering the present facile synthesis and itshigh efficacy,the present work may provide new insights into preparing high‐performance photocatalytic materials
基金financially supported by the National Natural Science Foundation of China (Nos.52170155 and 52100084)。
文摘Piezocatalytic activation of persulfate(PS) has great application potential in environmental remediation;however,the relationship between piezocatalyst thickness and catalytic activity is not clear,limiting the further improvement of catalytic activity and application of the technology.Herein,the Bi_(2)Fe_(4)O_(9)(BFO) piezocatalysts with tunable thickness were prepared through a facile hydrothermal method by tuning the molar ratio of Bi(NO_(3)),5H_(2)O and FeCl_(3)·6H_(2)O for piezocatalytic activation of peroxydisulfate(PDS).The BFO with the smallest thickness exhibits excellent catalytic activity,and the SO_(4)^(·-)and ·OH are the major reactive oxygen species for degrading organic pollutants.Further XPS investigations and finite element analyses demonstrate that the decreased thickness of BFO not only exposes more Fe^(2+)sites for PDS activation,but also improve the piezoelectric effect to accelerate the regeneration of Fe^(2+),thus enabling an enhanced synergy effect between PDS activation and piezocatalysis for outstanding catalytic activity.This work provides an understanding of the relationship between thickness of piezocatalysts and its catalytic activity over PDS activation,facilitating the development of more efficient piezocatalysts and PS-based advanced oxidation processes.
文摘The development of an active, durable, and metal-free carbocatalyst that is able to replace metal-based catalysts is of increasing scientific and technological importance. The use of such a catalyst would avoid problems caused by metal- containing catalysts, for example, environmental pollution by heavy metals and depletion of rare metal resources. Herein, an active and durable graphene carbocatalyst is presented for the carbocatalytic conversion of 4-nitrophenol to 4-aminophenol at ambient temperature. The carbocatalyst was prepared via a mild, water-based reaction between L-ascorbic acid （AA） and graphene oxide （GO） and did not involve any other reactants. During the structure and catalytic property optimization, a series of carbocatalysts were fabricated at various reaction temperatures and AA/GO ratios. Using several characterization techniques, detailed structural features of these carbocatalysts were identified. Possible active species and sites on the carbocatalysts were also identified such as certain oxygen-containing groups, the ~x-conjugated system, and graphene sheet edges. In addition, the synergistic effect between these active species and sites on the resulting catalytic activity is highlighted. Furthermore, we clarified the origin of the high stability and durability of the optimized carbocatalyst. The work presented here aids the design of high-performance carbocatalysts for hydrogenation reactions, and increases understanding of the structural and mechanistic aspects at the molecular level that lead to high catalyst activity and durability.
基金supported by the National Natural Science Foundation of China(Nos.51904115,52072151,52171211,52271218,and U22A20145)Taishan Scholars(No.ts201712050)+1 种基金Jinan Independent Innovative Team(No.2020GXRC015)Major Program of Shandong Province Natural Science Foundation(No.ZR2021ZD05).
文摘Na_(3)V_(2)(PO_(4))_(3)(NVP),as a great potential cathode candidate for Na-ion batteries(NIBs),has attracted enormous interest due to its three-dimensional(3D)large open framework for convenient Na+transport,yet its practical application is still limited by its inferior electron conductivity and sluggish Na+diffusion kinetics.Herein,the tiny Cr doped hierarchical NVP micro-flower cathodes(i.e.,Na_(3)V_(2-x)Crx(PO_(4))_(3)@C,x≤0.1),which are self-assembled with single-crystal nanoflake subunits in-situ coated with carbon nano-shell,are designed and fabricated via a scalable avenue.The optimized cathode,i.e.,Na_(3)V_(1.94)Cr_(0.06)(PO_(4))_(3)@C(NVCP-6),was endowed with more electro-active Na(2)sites and higher electronic/ionic conductivity for efficient sodium storage.Benefiting from these competitive merits,the NVCP-6,when evaluated as a cathode towards NIBs,exhibits an ultrahigh-rate capability of 99.8 mAh·g^(-1)at 200 C and superior stability of 82.2%over 7300 cycles at 50 C.Furthermore,the NVCP-6 based full NIBs display remarkable electrochemical properties in terms of both high-rate capacities and long-duration cycling properties at different temperatures(-20–50°C).The contribution,i.e.,the design of“four ounces can move a thousand pounds”,here will promote the practical industrial application of NVP towards advanced NIBs.
