The development of active yet stable catalysts for oxygen reduction reaction(ORR)is still a major issue for the extensive permeation of fuel cells into everyday technology.While nanostructured Pt catalysts are to date...The development of active yet stable catalysts for oxygen reduction reaction(ORR)is still a major issue for the extensive permeation of fuel cells into everyday technology.While nanostructured Pt catalysts are to date the best available systems in terms of activity,the same is not true for stability,particularly under operating conditions.In this work,Pt_(Х)Y alloy nanoparticles are proposed as active and durable electrocatalysts for ORR.Pt_(Х)Y nanoalloys are synthesized and further optimized by laser ablation in liquid followed by laser fragmentation in liquid.The novel integrated laser-assisted methodology succeeded in producing Pt_(Х)Y nanoparticles with the ideal size(<10 nm)of commercial Pt catalysts,yet resulting remarkably more active with E_(1/2)=0.943 V vs.RHE,specific activity=1095μA cm^(-2) and mass activity>1000 A g^(-1).At the same time,the nanoalloys are embedded in a fine Pt oxide matrix,which allows a greater stability of the catalyst than the commercial Pt reference,as directly verified on a gas diffusion electrode.展开更多
Bimetallic Pt-skin catalyst is a class of near-surface alloy(NSA)that owns a high degree of control over composition.Herein,density functional theory(DFT)is used to calculate the energetics of oxygen reduction reactio...Bimetallic Pt-skin catalyst is a class of near-surface alloy(NSA)that owns a high degree of control over composition.Herein,density functional theory(DFT)is used to calculate the energetics of oxygen reduction reaction(ORR)on Pt-skin over Ir,Pd and Au substrates.A Brønsted-Evans-Polanyi(BEP)relationship can be determined for the oxygen molecule dissociation.The binding energy of both atomic oxygen and hydroxyl radical is found to correlate well with the d band center of Pt-skin atoms.Their catalytic activities show the volcano relationship as the positions of each substrate in the periodic table.The effect of surface strain,band structure and charge transfer on the d band center is well studied,and it can be found that the surface strain effect plays a dominant role for all Pt-skin catalysts.Ir substrate makes the d band center of Pt-skin go far away from the Fermi level,while Au substrate makes it move towards the Fermi level.Being different from both Ir and Au,Pd substrate makes the d band center of Pt-skin comparable with the monometallic Pt.展开更多
Developing an e cient and durable oxygen reduction electrocatalyst is critical for clean-energy technology, such as fuel cells and metal–air batteries. In this study, we developed a facile strategy for the preparatio...Developing an e cient and durable oxygen reduction electrocatalyst is critical for clean-energy technology, such as fuel cells and metal–air batteries. In this study, we developed a facile strategy for the preparation of flexible, porous, and well-dispersed metal–heteroatom-doped carbon nanofibers by direct carbonization of electrospun Zn/Co-ZIFs/PAN nanofibers(Zn/Co-ZIFs/PAN). The obtained Zn/Co and N co-doped porous carbon nanofibers carbonized at 800 °C(Zn/Co–N@PCNFs-800) presented a good flexibility, a continuous porous structure, and a superior oxygen reduction reaction(ORR) catalytic activity to that of commercial 20 wt% Pt/C, in terms of its onset potential(0.98 V vs. RHE), half-wave potential(0.89 V vs. RHE), and limiting current density(-5.26 mA cm^(-2)). In addition, we tested the suitability and durability of Zn/Co–N@PCNFs-800 as the oxygen cathode for a rechargeable Zn–air battery. The prepared Zn–air batteries exhibited a higher power density(83.5 mW cm^(-2)), a higher specific capacity(640.3 mAh g^(-1)), an excellent reversibility, and a better cycling life than the commercial 20 wt% Pt/C + RuO_2 catalysts. This design strategy of flexible porous non-precious metal-doped ORR electrocatalysts obtained from electrospun ZIFs/polymer nanofibers could be extended to fabricate other novel, stable, and easy-to-use multi-functional electrocatalysts for clean-energy technology.展开更多
Nitrogen doped carbons are an important family of materials with ideal activity for oxygen reduction reaction(ORR). It is always interesting to search functional carbons with high heteroatom contents and desirable str...Nitrogen doped carbons are an important family of materials with ideal activity for oxygen reduction reaction(ORR). It is always interesting to search functional carbons with high heteroatom contents and desirable structure for ORR. Within this study, the surface modification of carbon nanotubes(CNTs) via hydrothermal carbonization(HTC) technique in the presence of glucose and urea was reported, where the surface of CNTs is successfully coated by nitrogen containing hydrothermal carbon layers. The resulting composite combines both advantages of the outstanding electrical conductivity of CNTs and the effective ORR active sites provided by doped nitrogen in the HTC carbon layers. By controlling the ratio of glucose and urea, the nitrogen contents coated on the surface of CNTs can reach up to 1.7 wt%. The resulting materials show outstanding electrochemical activity towards ORR in alkaline electrolyte, making it one of the valuable metal-free electrode materials and a competent alternative to the state-of-the-art Pt/C catalyst.展开更多
A trigonometric series expansion method and two similar modified methods for the Orr-Sommerfeld equation are presented. These methods use the trigonometric series expansion with an auxiliary function added to the high...A trigonometric series expansion method and two similar modified methods for the Orr-Sommerfeld equation are presented. These methods use the trigonometric series expansion with an auxiliary function added to the highest order derivative of the unknown function and generate the lower order derivatives through successive integra- tions. The proposed methods are easy to implement because of the simplicity of the chosen basis functions. By solving the plane Poiseuille flow (PPF), plane Couette flow (PCF), and Blasius boundary layer flow with several homogeneous boundary conditions, it is shown that these methods yield results with the same accuracy as that given by the conventional Chebyshev collocation method but with better robustness, and that ob- tained by the finite difference method but with fewer modal number.展开更多
Replacing fossil fuels with fuel cells is a feasible way to reduce global energy shortages and environmental pollution.However,the oxygen reduction reaction(ORR)at the cathode has sluggish kinetics,which limits the de...Replacing fossil fuels with fuel cells is a feasible way to reduce global energy shortages and environmental pollution.However,the oxygen reduction reaction(ORR)at the cathode has sluggish kinetics,which limits the development of fuel cells.It is significant to develop catalysts with high catalytic activity of ORR.The single-atom catalysts(SACs)of Pt supported on heteroatom-doped graphene are potential candidates for ORR.Here we studied the SACs of Pt with different heteroatoms doping and screened out Pt-C_(4) and Pt-C_(3)O_(1) structures with only 0.13 V overpotential for ORR.Meanwhile,it is found that B atoms doping could weaken the adsorption capacity of Pt,while N or O atoms doping could enhance it.This regularity was verified on Fe SACs.Through the electronic interaction analysis between Pt and adsorbate,we explained the mechanism of this regularity and further proposed a new descriptor named corrected d-band center(ε_(d-corr))to describe it.This descriptor is an appropriate reflection of the number of free electrons of the SACs,which could evaluate its adsorption capacity.Our work provides a purposeful regulatory strategy for the design of ORR catalysts.展开更多
Reasonable construction of high activity and low cost non-noble metal oxygen reduction reaction(ORR)catalyst is of great importance for the wide application of zinc-air batteries(ZABs).Using bimetallic MOF as a precur...Reasonable construction of high activity and low cost non-noble metal oxygen reduction reaction(ORR)catalyst is of great importance for the wide application of zinc-air batteries(ZABs).Using bimetallic MOF as a precursor combined with electrospinning,high-temperature carbonization and electrodeposition,we successfully developed a porous carbon nanofiber(Co@Fe-CNFs-1000)with bimetallic active center as an efficient catalyst for ORR.The successful construction of this special core-shell structure directly explores the synergy between different active centers.The results showed that the synthesized Co@Fe-CNFs-1000 catalyst exhibited ORR performance comparable to that of Pt/C in 0.1 mol/L KOH electrolyte,high half-wave potential(E_(1/2)=0.81 V)and limiting current density(J_(L)=5.4 mA·cm^(-2)).In addition,homemade liquid ZABs with Co@Fe-CNFs-1000 as the air cathode showed excellent power density(155.8 mW·cm^(-2)),specific capacity(780.6 mAh·g_(Zn)^(-1))and long-term stability(over 100 h at 2 mA·cm^(-2)),surpassing even Pt/C-based batteries.In addition,the flexible solid-state ZABs assembled based on Co@Fe-CNFs-1000 demonstrates excellent flexibility and durability.This work provides a new idea for constructing ORR catalysts with high activity centers.展开更多
Antibiotic pollution in aqueous solutions seriously endangers the natural environment and public health.In this work,Mo-doped transition metal FeCo–Se metal aerogels(MAs)were investigated as bifunctional catalysts fo...Antibiotic pollution in aqueous solutions seriously endangers the natural environment and public health.In this work,Mo-doped transition metal FeCo–Se metal aerogels(MAs)were investigated as bifunctional catalysts for the removal of sulfamethazine(SMT)in solution.The optimal Mo_(0.3)Fe_(1)Co_(3)–Se catalyst can remove 97.7% of SMT within 60 min(SMT content:10 mg/L,current intensity:10 mA/cm 2).The unique porous cross-linked structure of aerogel confered the catalyst sufficient active sites and efficient mass transfer channels.For the anode,Mo_(0.3)Fe_(1)Co_(3)–Se MAs exhibits superior oxygen evolution reaction(OER)property,with an overpotential of only 235 mV(10 mA/cm 2).Compared with Fe_(1)Co_(3) MAs or Mo_(0.3)Fe_(1)Co_(3) MAs,density functional theory(DFT)demonstrated that the better catalytic capacity of Mo_(0.3)Fe_(1)Co_(3)–Se MAs is attributed to the doping of Mo species and selenization lowers the energy barrier for the*OOH to O_(2) step in the OER process.Excellent OER perfor-mance ensures the self-oxygenation in this system,avoiding the addition of air or oxygen in the traditional electro-Fenton process.For the cathode,Mo doping can lead to the lattice contraction and metallic character of CoSe_(2),which is beneficial to accelerate electron transfer.The adjacent Co active sites effectively adsorb*OOH and inhibit the breakage of the O–O bond.Rotating ring disk electrode(RRDE)test indicated that Mo_(0.3)Fe_(1)Co_(3)–Se MAs has an excellent 2e^(-)ORR activity with H_(2)O_(2) selectivity up to 88%,and the generated H_(2)O_(2) is activated by the adjacent Fe site through heterogeneous Fenton process to generate⋅OH.展开更多
基金the P-DISC Grant PROMETEO(project number:P-DiSC#03NExuS_BIRD2021-UNIPD)DYNAMO(project number:P-P-DiSC#01BIRD2020-UNIPD)the financial support of the Fellowship in Applied Electrochemistry 2020。
文摘The development of active yet stable catalysts for oxygen reduction reaction(ORR)is still a major issue for the extensive permeation of fuel cells into everyday technology.While nanostructured Pt catalysts are to date the best available systems in terms of activity,the same is not true for stability,particularly under operating conditions.In this work,Pt_(Х)Y alloy nanoparticles are proposed as active and durable electrocatalysts for ORR.Pt_(Х)Y nanoalloys are synthesized and further optimized by laser ablation in liquid followed by laser fragmentation in liquid.The novel integrated laser-assisted methodology succeeded in producing Pt_(Х)Y nanoparticles with the ideal size(<10 nm)of commercial Pt catalysts,yet resulting remarkably more active with E_(1/2)=0.943 V vs.RHE,specific activity=1095μA cm^(-2) and mass activity>1000 A g^(-1).At the same time,the nanoalloys are embedded in a fine Pt oxide matrix,which allows a greater stability of the catalyst than the commercial Pt reference,as directly verified on a gas diffusion electrode.
基金This work was supported by the Projects of International Cooperation and Exchanges NSFC(No.21761162015)the Foundation and Frontier Research Project of Chongqing of China(cstc2018jcyjAX0513)the Science and Technology Research Program of Chongqing Municipal Education Commission(KJQN201801125).
文摘Bimetallic Pt-skin catalyst is a class of near-surface alloy(NSA)that owns a high degree of control over composition.Herein,density functional theory(DFT)is used to calculate the energetics of oxygen reduction reaction(ORR)on Pt-skin over Ir,Pd and Au substrates.A Brønsted-Evans-Polanyi(BEP)relationship can be determined for the oxygen molecule dissociation.The binding energy of both atomic oxygen and hydroxyl radical is found to correlate well with the d band center of Pt-skin atoms.Their catalytic activities show the volcano relationship as the positions of each substrate in the periodic table.The effect of surface strain,band structure and charge transfer on the d band center is well studied,and it can be found that the surface strain effect plays a dominant role for all Pt-skin catalysts.Ir substrate makes the d band center of Pt-skin go far away from the Fermi level,while Au substrate makes it move towards the Fermi level.Being different from both Ir and Au,Pd substrate makes the d band center of Pt-skin comparable with the monometallic Pt.
基金the Natural Science Foundation of Jiangsu Province (Grant No. BK20171200) for their financial support
文摘Developing an e cient and durable oxygen reduction electrocatalyst is critical for clean-energy technology, such as fuel cells and metal–air batteries. In this study, we developed a facile strategy for the preparation of flexible, porous, and well-dispersed metal–heteroatom-doped carbon nanofibers by direct carbonization of electrospun Zn/Co-ZIFs/PAN nanofibers(Zn/Co-ZIFs/PAN). The obtained Zn/Co and N co-doped porous carbon nanofibers carbonized at 800 °C(Zn/Co–N@PCNFs-800) presented a good flexibility, a continuous porous structure, and a superior oxygen reduction reaction(ORR) catalytic activity to that of commercial 20 wt% Pt/C, in terms of its onset potential(0.98 V vs. RHE), half-wave potential(0.89 V vs. RHE), and limiting current density(-5.26 mA cm^(-2)). In addition, we tested the suitability and durability of Zn/Co–N@PCNFs-800 as the oxygen cathode for a rechargeable Zn–air battery. The prepared Zn–air batteries exhibited a higher power density(83.5 mW cm^(-2)), a higher specific capacity(640.3 mAh g^(-1)), an excellent reversibility, and a better cycling life than the commercial 20 wt% Pt/C + RuO_2 catalysts. This design strategy of flexible porous non-precious metal-doped ORR electrocatalysts obtained from electrospun ZIFs/polymer nanofibers could be extended to fabricate other novel, stable, and easy-to-use multi-functional electrocatalysts for clean-energy technology.
基金The Award Program for Fujian Minjiang Scholar Professorship is acknowledged for financial supportfinancial support from the National Natural Science Foundation of China(NSFC Grant number 21571035)
文摘Nitrogen doped carbons are an important family of materials with ideal activity for oxygen reduction reaction(ORR). It is always interesting to search functional carbons with high heteroatom contents and desirable structure for ORR. Within this study, the surface modification of carbon nanotubes(CNTs) via hydrothermal carbonization(HTC) technique in the presence of glucose and urea was reported, where the surface of CNTs is successfully coated by nitrogen containing hydrothermal carbon layers. The resulting composite combines both advantages of the outstanding electrical conductivity of CNTs and the effective ORR active sites provided by doped nitrogen in the HTC carbon layers. By controlling the ratio of glucose and urea, the nitrogen contents coated on the surface of CNTs can reach up to 1.7 wt%. The resulting materials show outstanding electrochemical activity towards ORR in alkaline electrolyte, making it one of the valuable metal-free electrode materials and a competent alternative to the state-of-the-art Pt/C catalyst.
基金supported by the National Natural Science Foundation of China(Nos.11221062,11521091,and 91752203)
文摘A trigonometric series expansion method and two similar modified methods for the Orr-Sommerfeld equation are presented. These methods use the trigonometric series expansion with an auxiliary function added to the highest order derivative of the unknown function and generate the lower order derivatives through successive integra- tions. The proposed methods are easy to implement because of the simplicity of the chosen basis functions. By solving the plane Poiseuille flow (PPF), plane Couette flow (PCF), and Blasius boundary layer flow with several homogeneous boundary conditions, it is shown that these methods yield results with the same accuracy as that given by the conventional Chebyshev collocation method but with better robustness, and that ob- tained by the finite difference method but with fewer modal number.
基金supported by the National Key R&D Program of China(Nos.2022YFA1503100 and 2022YFA1503102)the National Natural Science Foundation of China(No.22273050)the Natural Science Foundation of Shandong Province(Nos.YDZX2021001 and ZR2022MB098).
文摘Replacing fossil fuels with fuel cells is a feasible way to reduce global energy shortages and environmental pollution.However,the oxygen reduction reaction(ORR)at the cathode has sluggish kinetics,which limits the development of fuel cells.It is significant to develop catalysts with high catalytic activity of ORR.The single-atom catalysts(SACs)of Pt supported on heteroatom-doped graphene are potential candidates for ORR.Here we studied the SACs of Pt with different heteroatoms doping and screened out Pt-C_(4) and Pt-C_(3)O_(1) structures with only 0.13 V overpotential for ORR.Meanwhile,it is found that B atoms doping could weaken the adsorption capacity of Pt,while N or O atoms doping could enhance it.This regularity was verified on Fe SACs.Through the electronic interaction analysis between Pt and adsorbate,we explained the mechanism of this regularity and further proposed a new descriptor named corrected d-band center(ε_(d-corr))to describe it.This descriptor is an appropriate reflection of the number of free electrons of the SACs,which could evaluate its adsorption capacity.Our work provides a purposeful regulatory strategy for the design of ORR catalysts.
基金financially supported by a key project of the State Key Laboratory of Bio-Fibers and Eco-Textiles of Qingdao University(No.RZ2000003348)Major Scientific and Technological Innovation Projects of Shandong Province(No.RZ2000001594).
文摘Reasonable construction of high activity and low cost non-noble metal oxygen reduction reaction(ORR)catalyst is of great importance for the wide application of zinc-air batteries(ZABs).Using bimetallic MOF as a precursor combined with electrospinning,high-temperature carbonization and electrodeposition,we successfully developed a porous carbon nanofiber(Co@Fe-CNFs-1000)with bimetallic active center as an efficient catalyst for ORR.The successful construction of this special core-shell structure directly explores the synergy between different active centers.The results showed that the synthesized Co@Fe-CNFs-1000 catalyst exhibited ORR performance comparable to that of Pt/C in 0.1 mol/L KOH electrolyte,high half-wave potential(E_(1/2)=0.81 V)and limiting current density(J_(L)=5.4 mA·cm^(-2)).In addition,homemade liquid ZABs with Co@Fe-CNFs-1000 as the air cathode showed excellent power density(155.8 mW·cm^(-2)),specific capacity(780.6 mAh·g_(Zn)^(-1))and long-term stability(over 100 h at 2 mA·cm^(-2)),surpassing even Pt/C-based batteries.In addition,the flexible solid-state ZABs assembled based on Co@Fe-CNFs-1000 demonstrates excellent flexibility and durability.This work provides a new idea for constructing ORR catalysts with high activity centers.
基金Thanks for the support of the National Natural Science Foundation of China(No.21776308)in this work.
文摘Antibiotic pollution in aqueous solutions seriously endangers the natural environment and public health.In this work,Mo-doped transition metal FeCo–Se metal aerogels(MAs)were investigated as bifunctional catalysts for the removal of sulfamethazine(SMT)in solution.The optimal Mo_(0.3)Fe_(1)Co_(3)–Se catalyst can remove 97.7% of SMT within 60 min(SMT content:10 mg/L,current intensity:10 mA/cm 2).The unique porous cross-linked structure of aerogel confered the catalyst sufficient active sites and efficient mass transfer channels.For the anode,Mo_(0.3)Fe_(1)Co_(3)–Se MAs exhibits superior oxygen evolution reaction(OER)property,with an overpotential of only 235 mV(10 mA/cm 2).Compared with Fe_(1)Co_(3) MAs or Mo_(0.3)Fe_(1)Co_(3) MAs,density functional theory(DFT)demonstrated that the better catalytic capacity of Mo_(0.3)Fe_(1)Co_(3)–Se MAs is attributed to the doping of Mo species and selenization lowers the energy barrier for the*OOH to O_(2) step in the OER process.Excellent OER perfor-mance ensures the self-oxygenation in this system,avoiding the addition of air or oxygen in the traditional electro-Fenton process.For the cathode,Mo doping can lead to the lattice contraction and metallic character of CoSe_(2),which is beneficial to accelerate electron transfer.The adjacent Co active sites effectively adsorb*OOH and inhibit the breakage of the O–O bond.Rotating ring disk electrode(RRDE)test indicated that Mo_(0.3)Fe_(1)Co_(3)–Se MAs has an excellent 2e^(-)ORR activity with H_(2)O_(2) selectivity up to 88%,and the generated H_(2)O_(2) is activated by the adjacent Fe site through heterogeneous Fenton process to generate⋅OH.
