碳化铁θ-Fe_(3)C作为费托反应活性相之一,其氧化造成了催化剂的严重失活。探究氧原子在碳化铁晶面的吸附及移除机理有助于理解氧化过程,为提高催化剂的稳定性提供参考。本工作通过理论计算研究了低覆盖度下氧原子在θ-Fe_(3)C不同晶面...碳化铁θ-Fe_(3)C作为费托反应活性相之一,其氧化造成了催化剂的严重失活。探究氧原子在碳化铁晶面的吸附及移除机理有助于理解氧化过程,为提高催化剂的稳定性提供参考。本工作通过理论计算研究了低覆盖度下氧原子在θ-Fe_(3)C不同晶面的吸附,其在(110)晶面吸附最强,(001)晶面次之,(011)晶面吸附最弱,即(110)容易氧化。原子热力学研究表明,增大H_(2)O分压或降低温度有利于氧原子吸附,容易造成表面氧化。此外,在典型费托反应条件下(110)晶面氧原子的覆盖度最高,进一步证明该晶面易氧化,与低覆盖度吸附结果一致。对移除路径进行计算得出,(011)晶面吸附氧原子直接与CO反应以CO_(2)方式移除能垒较低(0.84 eV);(001)与(110)晶面吸附氧原子主要通过OH歧化以H_(2)O方式移除,但后者形成O−H键需要克服的能垒更高(1.72 vs 1.47 eV)。展开更多
The impedance matching of absorbers is a vital factor affecting their microwave absorption(MA)properties.In this work,we controllably synthesized Material of Institute Lavoisier 88C(MIL-88C)with varying aspect ratios(...The impedance matching of absorbers is a vital factor affecting their microwave absorption(MA)properties.In this work,we controllably synthesized Material of Institute Lavoisier 88C(MIL-88C)with varying aspect ratios(AR)as a precursor by regulating oil bath conditions,followed by one-step thermal decomposition to obtain carbon-coated iron-based composites.Modifying the precursor MIL-88C(Fe)preparation conditions,such as the molar ratio between metal ions and organic ligands(M/O),oil bath temperature,and oil bath time,influenced the phases,graphitization degree,and AR of the derivatives,enabling low filler loading,achieving well-matched impedance,and ensuring outstanding MA properties.The MOF-derivatives 2(MD_(2))/polyvinylidene Difluoride(PVDF),MD_(3)/PVDF,and MD4/PVDF absorbers all exhibited excellent MA properties with optimal filler loadings below 20 wt%and as low as 5 wt%.The MD_(2)/PVDF(5 wt%)achieved a maximum effective absorption bandwidth(EAB)of 5.52 GHz(1.90 mm).The MD_(3)/PVDF(10 wt%)possessed a minimum reflection loss(RL_(min))value of−67.4 at 12.56 GHz(2.13 mm).A symmetric gradient honeycomb structure(SGHS)was constructed utilizing the high-frequency structure simulator(HFSS)to further extend the EAB,achieving an EAB of 14.6 GHz and a RL_(min) of−59.0 dB.This research offers a viable inspiration to creating structures or materials with high-efficiency MA properties.展开更多
Efficient bifunctional oxygen electrocatalysts for ORR and OER are fundamental to the development of high performance metal-air batteries.Herein,a facile cost-efficient two-step pyrolysis strategy for the fabrication ...Efficient bifunctional oxygen electrocatalysts for ORR and OER are fundamental to the development of high performance metal-air batteries.Herein,a facile cost-efficient two-step pyrolysis strategy for the fabrication of a bifunctional oxygen electrocatalyst has been proposed.The efficient non-preciousmetal-based electrocatalyst,Fe/Fe_(3)C@Fe-N_(x)-C consists of highly curved onion-like carbon shells that encapsulate Fe/Fe_(3)C nanoparticles,distributed on an extensively porous graphitic carbon aerogel.The obtained Fe/Fe_(3)C@Fe-N_(x)-C aerogel exhibited superb electrochemical activity,excellent durability,and high methanol tolerance.The experimental results indicated that the assembly of onion-like carbon shells with encapsulated Fe/Fe_(3)C yielded highly curved carbon surfaces with abundant Fe-Nxactive sites,a porous structure,and enhanced electrocatalytic activity towards ORR and OER,hence displaying promising potential for application as an air cathode in rechargeable Zn-air batteries.The constructed Zn-air battery possessed an exceptional peak power density of~147 mW cm^(-2),outstanding cycling stability(200 cycles,1 h per cycle),and a small voltage gap of 0.87 V.This study offers valuable insights regarding the construction of low-cost and highly active bifunctional oxygen electrocatalysts for efficient air batteries.展开更多
The improvement of catalysts’stability under harsh reaction conditions is vital for their practical applica-bility.Herein,iron carbide(Fe_(3)C)nanoparticles were encapsulated in graphitic carbon in situ and a carbon ...The improvement of catalysts’stability under harsh reaction conditions is vital for their practical applica-bility.Herein,iron carbide(Fe_(3)C)nanoparticles were encapsulated in graphitic carbon in situ and a carbon ball served as the carrier.The synthesized Fe_(3)C@C/C was first utilized to treat an m-cresol wastewater containing Si via catalytic ozonation.Compared with the commercial Fe/Al_(2)O_(3)catalyst,the resistance to Si of the Fe_(3)C@C/C was improved 22.68 times,while the TOC removal rate increased by a factor of 2.9,and it remained stable during 10 cycles and 12000 min of continuous reaction,which further demon-strated its potential for diverse applications.The catalyst exhibits improved resistance to Si because of the dual protection from the carbon-encapsulated structure and carbon carrier.Density functional theory calculations show that the encapsulation of Fe_(3)C using carbon significantly increases the resistance to adsorption of Si on its active sites.In addition,the activation of O_(3)is unimpeded on the Fe_(3)C adsorption sites by the protection from C,thus the generation of reactive oxygen species(ROS)by ozone is largely promoted.The mechanism associated with the resistance of the Fe_(3)C@C/C catalyst to Si and its elevated activity are also elucidated.展开更多
This work demonstrated that Enteromorpha biochar with introduced iron(SFB900-3)could activate peroxymonosulfate(PMS)efficiently for NTP remediation.It removed 83.9%-95.1%of NTP in 60 min under a wide pH range from 3.1...This work demonstrated that Enteromorpha biochar with introduced iron(SFB900-3)could activate peroxymonosulfate(PMS)efficiently for NTP remediation.It removed 83.9%-95.1%of NTP in 60 min under a wide pH range from 3.15 to 8.95.Density functional theory(DFT)calculations revealed the synergistic relationship between internal Fe single atoms and introduced Fe compounds—Fe_(3)C.The adsorption capacity of SFB900-3 for persulfate improved from−0.953 eV to−4.214 eV,and the Bader charge analysis showed that Fe atoms as active sites(0.658 e)enhanced the adsorption capacity more than carbon(0.050 e).Moreover,the energy barrier for PMS dissociation reduced from 0.072 eV to−5.372 eV due to the longer length of O-O bond under the synergistic effect of Fe single atom and Fe_(3)C which increased from 1.467Åto 3.890ÅThe quenching experiment confirmed that ^(1)O_(2) was the main active substance in NTP degradation and its contribution rate was 88.2%,which was further verified by EPR detection.The effect factor experiments proved that the SFB900-3/PMS system had stable and efficient activity for NTP removal,which remained at 73.6%removal rate after three rounds of tests.This work provided novel guidance for constructing efficient and stable biochar-based materials for organic pollutant remediation.展开更多
文摘碳化铁θ-Fe_(3)C作为费托反应活性相之一,其氧化造成了催化剂的严重失活。探究氧原子在碳化铁晶面的吸附及移除机理有助于理解氧化过程,为提高催化剂的稳定性提供参考。本工作通过理论计算研究了低覆盖度下氧原子在θ-Fe_(3)C不同晶面的吸附,其在(110)晶面吸附最强,(001)晶面次之,(011)晶面吸附最弱,即(110)容易氧化。原子热力学研究表明,增大H_(2)O分压或降低温度有利于氧原子吸附,容易造成表面氧化。此外,在典型费托反应条件下(110)晶面氧原子的覆盖度最高,进一步证明该晶面易氧化,与低覆盖度吸附结果一致。对移除路径进行计算得出,(011)晶面吸附氧原子直接与CO反应以CO_(2)方式移除能垒较低(0.84 eV);(001)与(110)晶面吸附氧原子主要通过OH歧化以H_(2)O方式移除,但后者形成O−H键需要克服的能垒更高(1.72 vs 1.47 eV)。
基金financially supported by the National Natural Science Foundation of China(51972049,52073010,and 52373259)the Projects of the Science and Technology Department of Jilin Province(20230201132GX)the Projects of the Education Department of Jilin Province(JJKH20220123KJ)。
文摘The impedance matching of absorbers is a vital factor affecting their microwave absorption(MA)properties.In this work,we controllably synthesized Material of Institute Lavoisier 88C(MIL-88C)with varying aspect ratios(AR)as a precursor by regulating oil bath conditions,followed by one-step thermal decomposition to obtain carbon-coated iron-based composites.Modifying the precursor MIL-88C(Fe)preparation conditions,such as the molar ratio between metal ions and organic ligands(M/O),oil bath temperature,and oil bath time,influenced the phases,graphitization degree,and AR of the derivatives,enabling low filler loading,achieving well-matched impedance,and ensuring outstanding MA properties.The MOF-derivatives 2(MD_(2))/polyvinylidene Difluoride(PVDF),MD_(3)/PVDF,and MD4/PVDF absorbers all exhibited excellent MA properties with optimal filler loadings below 20 wt%and as low as 5 wt%.The MD_(2)/PVDF(5 wt%)achieved a maximum effective absorption bandwidth(EAB)of 5.52 GHz(1.90 mm).The MD_(3)/PVDF(10 wt%)possessed a minimum reflection loss(RL_(min))value of−67.4 at 12.56 GHz(2.13 mm).A symmetric gradient honeycomb structure(SGHS)was constructed utilizing the high-frequency structure simulator(HFSS)to further extend the EAB,achieving an EAB of 14.6 GHz and a RL_(min) of−59.0 dB.This research offers a viable inspiration to creating structures or materials with high-efficiency MA properties.
基金supported financially by the National Natural Science Foundation of China,China(Grant No.51702180,51572136,91963113,21703116,51372127,51873096)The Scientific and Technical Development Project of Qingdao,China(Grant No.18-2-2-52-jch)+1 种基金The Taishan Scholar Advantage and Characteristic Discipline Team of Eco Chemical Process and TechnologyThe Natural Science Foundation of Hebei Province(B2019204009)。
文摘Efficient bifunctional oxygen electrocatalysts for ORR and OER are fundamental to the development of high performance metal-air batteries.Herein,a facile cost-efficient two-step pyrolysis strategy for the fabrication of a bifunctional oxygen electrocatalyst has been proposed.The efficient non-preciousmetal-based electrocatalyst,Fe/Fe_(3)C@Fe-N_(x)-C consists of highly curved onion-like carbon shells that encapsulate Fe/Fe_(3)C nanoparticles,distributed on an extensively porous graphitic carbon aerogel.The obtained Fe/Fe_(3)C@Fe-N_(x)-C aerogel exhibited superb electrochemical activity,excellent durability,and high methanol tolerance.The experimental results indicated that the assembly of onion-like carbon shells with encapsulated Fe/Fe_(3)C yielded highly curved carbon surfaces with abundant Fe-Nxactive sites,a porous structure,and enhanced electrocatalytic activity towards ORR and OER,hence displaying promising potential for application as an air cathode in rechargeable Zn-air batteries.The constructed Zn-air battery possessed an exceptional peak power density of~147 mW cm^(-2),outstanding cycling stability(200 cycles,1 h per cycle),and a small voltage gap of 0.87 V.This study offers valuable insights regarding the construction of low-cost and highly active bifunctional oxygen electrocatalysts for efficient air batteries.
基金This work was financially supported by the Youth Innovation Promotion Association CAS(No.2020190)the National Natural Science Foundation of China(No.52100072)+1 种基金the Scientific Research Common Program of Beijing Municipal,Commission of Education(No.KM202010017006)the Beijing Natural Science Foundation(No.8214056).
文摘The improvement of catalysts’stability under harsh reaction conditions is vital for their practical applica-bility.Herein,iron carbide(Fe_(3)C)nanoparticles were encapsulated in graphitic carbon in situ and a carbon ball served as the carrier.The synthesized Fe_(3)C@C/C was first utilized to treat an m-cresol wastewater containing Si via catalytic ozonation.Compared with the commercial Fe/Al_(2)O_(3)catalyst,the resistance to Si of the Fe_(3)C@C/C was improved 22.68 times,while the TOC removal rate increased by a factor of 2.9,and it remained stable during 10 cycles and 12000 min of continuous reaction,which further demon-strated its potential for diverse applications.The catalyst exhibits improved resistance to Si because of the dual protection from the carbon-encapsulated structure and carbon carrier.Density functional theory calculations show that the encapsulation of Fe_(3)C using carbon significantly increases the resistance to adsorption of Si on its active sites.In addition,the activation of O_(3)is unimpeded on the Fe_(3)C adsorption sites by the protection from C,thus the generation of reactive oxygen species(ROS)by ozone is largely promoted.The mechanism associated with the resistance of the Fe_(3)C@C/C catalyst to Si and its elevated activity are also elucidated.
基金National Natural Science Foundation of China(Grant No.52270156,51909089)Natural Science Foundation of Hunan Province,China(Grant No.2020JJ5252)Training Program for Excellent Young Innovators of Changsha(Grant No.kq2209015).
文摘This work demonstrated that Enteromorpha biochar with introduced iron(SFB900-3)could activate peroxymonosulfate(PMS)efficiently for NTP remediation.It removed 83.9%-95.1%of NTP in 60 min under a wide pH range from 3.15 to 8.95.Density functional theory(DFT)calculations revealed the synergistic relationship between internal Fe single atoms and introduced Fe compounds—Fe_(3)C.The adsorption capacity of SFB900-3 for persulfate improved from−0.953 eV to−4.214 eV,and the Bader charge analysis showed that Fe atoms as active sites(0.658 e)enhanced the adsorption capacity more than carbon(0.050 e).Moreover,the energy barrier for PMS dissociation reduced from 0.072 eV to−5.372 eV due to the longer length of O-O bond under the synergistic effect of Fe single atom and Fe_(3)C which increased from 1.467Åto 3.890ÅThe quenching experiment confirmed that ^(1)O_(2) was the main active substance in NTP degradation and its contribution rate was 88.2%,which was further verified by EPR detection.The effect factor experiments proved that the SFB900-3/PMS system had stable and efficient activity for NTP removal,which remained at 73.6%removal rate after three rounds of tests.This work provided novel guidance for constructing efficient and stable biochar-based materials for organic pollutant remediation.
