This study describes the kinetics and thermodynamics of the esterification of acidified oil with methanol catalyzed by sulfonated cation exchange resins(SCER). The effects of the mass ratio of methanol to acidified oi...This study describes the kinetics and thermodynamics of the esterification of acidified oil with methanol catalyzed by sulfonated cation exchange resins(SCER). The effects of the mass ratio of methanol to acidified oil,reaction temperature,and catalyst loading were studied to optimize the conditions for maximum conversion of free fatty acids(FFAs). The results showed that the optimal conversion rate of FFAs was 91.87% at the mass ratio of methanol to acidified oil of 2.5:1.0,reaction temperature of 65.0 °C,catalyst loading of 5.0 g and reaction time of 8.0 h. The external and internal mass transfer resistances were negligible based on the experimental results and a pseudo-homogeneous kinetic model was proposed for the esterification. The activation energy and thermodynamic parameters including G,S and H were determined. The conversion rates of FFAs obtained from the established model were in good agreement with the experimental data.展开更多
The hydrogen evolution reaction(HER)via water electrolysis has gained immense research attention.Seawater electrolysis provides great opportunities for sustainable energy production,but is extremely challenging.Transi...The hydrogen evolution reaction(HER)via water electrolysis has gained immense research attention.Seawater electrolysis provides great opportunities for sustainable energy production,but is extremely challenging.Transition metal phosphides are promising candidate electrocatalysts.Herein,we prepared a novel Fe-Co_(2)P bundle of nanorods(BNRs)for catalyzing the HER in seawater electrolysis and over the entire p H range.Cobalt phosphides with different crystal phases and morphologies were obtained by varying the Fe doping amount.The Co:Fe molar ratio of 1:0.5 was found to be optimum.The Fe doping improved the HER performance of Co_(2)P over the entire p H range by providing favorable electronic properties and morphology,lattice distortion,and special coordination environment.The Fe-Co_(2)P BNRs showed higher catalytic activity than 20%Pt/C in seawater at high potentials.The density functional theory calculations revealed that the Fe doping reduced the hydrogen binding strength of Co_(2)P to efficiently accelerate the HER kinetics and produce a favorable charge density.This study provides valuable insights into the design and development of high-efficiency HER catalysts for large-scale seawater electrolysis.展开更多
The development of low-cost, efficient, and high atomic economy electrocatalysts for hydrogen evolution reaction(HER) in the entire p H range for sustainable hydrogen production is of great importance but still challe...The development of low-cost, efficient, and high atomic economy electrocatalysts for hydrogen evolution reaction(HER) in the entire p H range for sustainable hydrogen production is of great importance but still challenging. Herein, we synthesize a highly dispersed N-doped carbon frames(NCFs) anchored with Co single atoms(SAs) and Co nanoparticles(NPs) catalyst by a doping-adsorption-pyrolysis strategy for electrocatalytic hydrogen evolution. The Co SAs-Co NPs/NCFs catalyst exhibits an excellent HER activity with small overpotential, low Tafel slope, high turnover frequency as well as remarkable stability. It also exhibits a superior HER performance in the entire p H range. Combining with experimental and theoretical calculation, we find that Co SAs with Co-N_(3) coordination structure and Co NPs have a strong interaction for promoting synergistic HER electrocatalytic process. The H_(2)O molecule is easily activated and dissociated on Co NPs, while the generated H^(*) is easily adsorbed on Co SAs for HER, which makes the Co SAs-Co NPs/NCFs catalyst exhibit more suitable H adsorption strength and more conducive to the activation and dissociation of H_(2)O molecules. This work not only proposes a novel idea for constructing coupling catalyst with atomic-level precision, but also provides strong reference for the development of high-efficiency HER electrocatalysts for practical application.展开更多
Large scale synthesis of high-efficiency bifunctional electrocatalyst based on cost-effective and earth-abundant transition metal for overall water splitting in the alkaline environment is indispensable for renewable ...Large scale synthesis of high-efficiency bifunctional electrocatalyst based on cost-effective and earth-abundant transition metal for overall water splitting in the alkaline environment is indispensable for renewable energy conversion.In this regard,meticulous design of active sites and probing their catalytic mechanism on both cathode and anode with different reaction environment at molecular-scale are vitally necessary.Herein,a coordination environment inheriting strategy is presented for designing low-coordination Ni^(2+)octahedra(L-Ni-8)atomic interface at a high concentration(4.6 at.%).Advanced spectroscopic techniques and theoretical calculations reveal that the self-matching electron delocalization and localization state at L-Ni-8 atomic interface enable an ideal reaction environment at both cathode and anode.To improve the efficiency of using the self-modification reaction environment at L-Ni-8,all of the structural features,including high atom economy,mass transfer,and electron transfer,are integrated together from atomic-scale to macro-scale.At high current density of 500 mA/cm2,the samples synthesized at gram-scale can deliver low hydrogen evolution reaction(HER)and oxygen evolution reaction(OER)overpotentials of 262 and 348 mV,respectively.展开更多
In the field of electrolysis of water,the design and synthesis of catalysts over a wide pH range have attracted extensive attentions.In this paper,Co and N are co-introduced into the structural unit of tungsten disulf...In the field of electrolysis of water,the design and synthesis of catalysts over a wide pH range have attracted extensive attentions.In this paper,Co and N are co-introduced into the structural unit of tungsten disulfide(WS_(2)),and the hydrogen evolution reaction(HER)performances of different WS_(2)-based catalysts are theoretically predicted and systematically studied by density functional theory(DFT)calculations.With the guidance of DFT calculations,an evaporation-pyrolysis strategy is applied to prepare Co and N co-doped WS_(2)(Co,N-WS_(2))flower-like nanosheets,which exhibits excellent HER performance over a wide pH range.In addition,the DFT calculations show that the active sites in Co,N-WS_(2) have a good ability of hydrogen adsorption after the introduction of Co and N,suggesting that such a co-doping system will be an ideal catalyst for oxidative dehydrogenation(ODH).The following experiment results indeed evidence that the Co,N-WS_(2) catalyst displays a high activity in the ODH of 1,2,3,4-tetrahydroquinoline(4H-quinoline)and its derivatives.Therefore,this work provides a good example for the rational design and accurate preparation of functional catalysts,which enables it possible to develop other efficient catalysts with multiple functions.展开更多
基金support from the Natural Science Foundation of Shandong Province (Grant no.ZR2013BL010)the Research Excellence Award of Shandong University of Technology and the Zibo Technology Research and Development Program of China (Grant no.2013GG04110)
文摘This study describes the kinetics and thermodynamics of the esterification of acidified oil with methanol catalyzed by sulfonated cation exchange resins(SCER). The effects of the mass ratio of methanol to acidified oil,reaction temperature,and catalyst loading were studied to optimize the conditions for maximum conversion of free fatty acids(FFAs). The results showed that the optimal conversion rate of FFAs was 91.87% at the mass ratio of methanol to acidified oil of 2.5:1.0,reaction temperature of 65.0 °C,catalyst loading of 5.0 g and reaction time of 8.0 h. The external and internal mass transfer resistances were negligible based on the experimental results and a pseudo-homogeneous kinetic model was proposed for the esterification. The activation energy and thermodynamic parameters including G,S and H were determined. The conversion rates of FFAs obtained from the established model were in good agreement with the experimental data.
基金the support by the Fundamental Research Funds for the Central Universities(No.19CX02008A)the China Postdoctoral Science Foundation(No.2018M642726)+1 种基金the Petro China Innovation Foundation(No.2019D-5007-0401)the Taishan Scholars Program of Shandong Province。
文摘The hydrogen evolution reaction(HER)via water electrolysis has gained immense research attention.Seawater electrolysis provides great opportunities for sustainable energy production,but is extremely challenging.Transition metal phosphides are promising candidate electrocatalysts.Herein,we prepared a novel Fe-Co_(2)P bundle of nanorods(BNRs)for catalyzing the HER in seawater electrolysis and over the entire p H range.Cobalt phosphides with different crystal phases and morphologies were obtained by varying the Fe doping amount.The Co:Fe molar ratio of 1:0.5 was found to be optimum.The Fe doping improved the HER performance of Co_(2)P over the entire p H range by providing favorable electronic properties and morphology,lattice distortion,and special coordination environment.The Fe-Co_(2)P BNRs showed higher catalytic activity than 20%Pt/C in seawater at high potentials.The density functional theory calculations revealed that the Fe doping reduced the hydrogen binding strength of Co_(2)P to efficiently accelerate the HER kinetics and produce a favorable charge density.This study provides valuable insights into the design and development of high-efficiency HER catalysts for large-scale seawater electrolysis.
基金supported by the Taishan Scholars Program of Shandong Province(tsqn201909065)the Shandong Provincial Natural Science Foundation(ZR2020QB174)+3 种基金the Petro China Innovation Foundation(2019D-5007-0401)the National Natural Science Foundation of China(21776315,22108306)the Fundamental Research Funds for the Central Universities(19CX02008A,19CX05001A)the Postgraduate Innovation Fund of China University of Petroleum(East China)(YCX2020037)。
文摘The development of low-cost, efficient, and high atomic economy electrocatalysts for hydrogen evolution reaction(HER) in the entire p H range for sustainable hydrogen production is of great importance but still challenging. Herein, we synthesize a highly dispersed N-doped carbon frames(NCFs) anchored with Co single atoms(SAs) and Co nanoparticles(NPs) catalyst by a doping-adsorption-pyrolysis strategy for electrocatalytic hydrogen evolution. The Co SAs-Co NPs/NCFs catalyst exhibits an excellent HER activity with small overpotential, low Tafel slope, high turnover frequency as well as remarkable stability. It also exhibits a superior HER performance in the entire p H range. Combining with experimental and theoretical calculation, we find that Co SAs with Co-N_(3) coordination structure and Co NPs have a strong interaction for promoting synergistic HER electrocatalytic process. The H_(2)O molecule is easily activated and dissociated on Co NPs, while the generated H^(*) is easily adsorbed on Co SAs for HER, which makes the Co SAs-Co NPs/NCFs catalyst exhibit more suitable H adsorption strength and more conducive to the activation and dissociation of H_(2)O molecules. This work not only proposes a novel idea for constructing coupling catalyst with atomic-level precision, but also provides strong reference for the development of high-efficiency HER electrocatalysts for practical application.
基金supported by the National Natural Science Foundation of China(No.21676300)the Shandong Provincial Natural Science Foundation(No.ZR2018MB035)+3 种基金the Fundamental Research Funds for the Central Universities(Nos.19CX02008A and 16CX06007A)PetroChina Innovation Foundation(No.2019D-5007-0401)Taishan Scholars Program of Shandong Province(No.tsqn201909065)Tsinghua University Initiative Scientific Research Program.
文摘Large scale synthesis of high-efficiency bifunctional electrocatalyst based on cost-effective and earth-abundant transition metal for overall water splitting in the alkaline environment is indispensable for renewable energy conversion.In this regard,meticulous design of active sites and probing their catalytic mechanism on both cathode and anode with different reaction environment at molecular-scale are vitally necessary.Herein,a coordination environment inheriting strategy is presented for designing low-coordination Ni^(2+)octahedra(L-Ni-8)atomic interface at a high concentration(4.6 at.%).Advanced spectroscopic techniques and theoretical calculations reveal that the self-matching electron delocalization and localization state at L-Ni-8 atomic interface enable an ideal reaction environment at both cathode and anode.To improve the efficiency of using the self-modification reaction environment at L-Ni-8,all of the structural features,including high atom economy,mass transfer,and electron transfer,are integrated together from atomic-scale to macro-scale.At high current density of 500 mA/cm2,the samples synthesized at gram-scale can deliver low hydrogen evolution reaction(HER)and oxygen evolution reaction(OER)overpotentials of 262 and 348 mV,respectively.
基金the National Natural Science Foundation of China(51902003 and 21771003)Anhui Province Natural Science Foundation(2008085QB53)the Natural Science Research Project of Anhui Province Education Department(KJ2019A0581)。
文摘发展廉价、高效的水氧化(OER)催化剂对发展可持续能源具有重要意义.杂原子掺杂调节活性位点的电子结构提高催化剂的OER性能被认为是一种高效的策略.本文通过水热法制备得到Mn掺杂的层状镍铁氢氧化物/还原氧化石墨烯(Mn-NiFe LDH/rGO)作为高效、稳定的水氧化催化剂.实验和模拟计算研究都表明Mn能调整活性位点的电子结构,改善其对水氧化反应中中间产物的吸附能垒,从而减小OER反应中决速步骤的反应势垒.具体而言,最优的Mn-NiFe LDH/rGO复合材料在过电位仅为240 mV就能驱动10 mA cm^(-2)的电流密度,Tafel斜率低至40.0 mV dec^(-1),并且具有良好的稳定性.该催化剂优异的活性优于最近报道的OER电催化剂.本工作为制备用于能源转换领域的高活性、廉价的电催化剂提供了新的思路.
基金the National Natural Science Foundation of China(Nos.21771003,51902003,and 21501004)the University Synergy Innovation Program of Anhui Province(No.GXXT-2021-020)+1 种基金the Natural Science Foundation of Anhui Province(No.2008085QB53)the Natural Science Research Project of Anhui Province Education Department(No.KJ2019A0581).
文摘In the field of electrolysis of water,the design and synthesis of catalysts over a wide pH range have attracted extensive attentions.In this paper,Co and N are co-introduced into the structural unit of tungsten disulfide(WS_(2)),and the hydrogen evolution reaction(HER)performances of different WS_(2)-based catalysts are theoretically predicted and systematically studied by density functional theory(DFT)calculations.With the guidance of DFT calculations,an evaporation-pyrolysis strategy is applied to prepare Co and N co-doped WS_(2)(Co,N-WS_(2))flower-like nanosheets,which exhibits excellent HER performance over a wide pH range.In addition,the DFT calculations show that the active sites in Co,N-WS_(2) have a good ability of hydrogen adsorption after the introduction of Co and N,suggesting that such a co-doping system will be an ideal catalyst for oxidative dehydrogenation(ODH).The following experiment results indeed evidence that the Co,N-WS_(2) catalyst displays a high activity in the ODH of 1,2,3,4-tetrahydroquinoline(4H-quinoline)and its derivatives.Therefore,this work provides a good example for the rational design and accurate preparation of functional catalysts,which enables it possible to develop other efficient catalysts with multiple functions.
