The application of naive Koutecky-Levich analysis to micro- and nano-particle modified rotating disk electrodes of partially covered and non-planar geometry is critically analysed. Assuming strong overlap of the diffu...The application of naive Koutecky-Levich analysis to micro- and nano-particle modified rotating disk electrodes of partially covered and non-planar geometry is critically analysed. Assuming strong overlap of the diffusion fields of the particles such that transport to the entire surface is time-independent and one-dimensional, the observed voltammetric response reflects an apparent electrochemical rate o constant koapp, equal to the true rate constant ko describing the redox reaction of interest on the surface of the nanoparticles and the ratio,ψ, of the total electroactive surface area to the geometric area of the rotating disk surface. It is demonstrated that Koutecky-Levich analysis is applicable and yields the expected plots of I-1 versus ω-1 where I is the current and ω is the rotation speed but that the values of the electrochemical rate constants inferred are thereof koapp, not ko. Thus, for ψ 〉 1 apparent electrocatalysis might be naively but wrongly inferred whereas for ψ 〈 1 the deduced electrochemical rate constant will be less than ko. Moreover, the effect of ψ on the observed rotating disk electrode voltammograms is significant, signalling the need for care in the overly simplistic application of Koutecky-Levich analysis to modified rotating electrodes, as is commonly applied for example in the analysis of possible oxygen reduction catalysts.展开更多
Plasma-synthesized cobalt oxide supported on carbon has been analyzed for its use for electrocatalytic oxygen reduction reaction （ORR） in alkaline anion exchange membrane fuel cells （AEMFC）. This work presents the...Plasma-synthesized cobalt oxide supported on carbon has been analyzed for its use for electrocatalytic oxygen reduction reaction （ORR） in alkaline anion exchange membrane fuel cells （AEMFC）. This work presents the ORR activity in 0.1 mol L-1 KOH and 0.1 tool L-1 K2CO3 at 25 ℃. Cyclic voltammetry （CV） was used to determine the potentials at which the ORR occurs and to evaluate the stability of catalyst. Moreover, a rotating ring-disk electrode （RRDE） was used to investigate the activity of the catalysts and the formation of the by-product hydroperoxide anion （HO2-） as well as to identify the preferred pathway of the ORR. Calculated kinetic parameters for the ORR for the cobalt catalysts are shown in this work together with a comparison to a commercial platinum catalyst. However, the cobalt oxide produced more by-products which could lead to damage of the membrane in a fuel cell through a radical attack of the polymer backbone.展开更多
Zinc-air battery is one of the most promising next-generation energy conversion and storage systems.Green and low-cost catalysts with high oxygen reduction reaction(ORR)catalytic activity are desired to meet the requi...Zinc-air battery is one of the most promising next-generation energy conversion and storage systems.Green and low-cost catalysts with high oxygen reduction reaction(ORR)catalytic activity are desired to meet the requirements of Zinc-air batteries.Herein,poly-active centric Co3O4-CeO2/Co-N-C(ketjenblack carbon)catalysts were prepared by a facile method.The Co3O4 and CeO2 nanoparticles are uniformly anchored on the surface of Co and N doped carbon support.The half-wave potential of Co3O4-CeO2/Co-N-C in the rotating disk electrode testing is close to that of Pt/C.The Zn-air battery using Co3O4-CeO2/Co-N-C as the cathode catalyst can provide a high specific capacity of 728 mA h g^-1 at 20 mA cm^-2 and maintain a stable discharge voltage.The remarkable catalytic performance is mainly attributed to the synergistic effect among Co3O4,CeO2 and Co-N-C,the outstanding electrical conductivity and the large surface area.Benefitting from the high catalytic activity,environmental friendliness and the facile synthesis process,Co3O4-CeO2/Co-N-C catalyst lends itself well to a great prospect in the application of metalair batteries.展开更多
文摘The application of naive Koutecky-Levich analysis to micro- and nano-particle modified rotating disk electrodes of partially covered and non-planar geometry is critically analysed. Assuming strong overlap of the diffusion fields of the particles such that transport to the entire surface is time-independent and one-dimensional, the observed voltammetric response reflects an apparent electrochemical rate o constant koapp, equal to the true rate constant ko describing the redox reaction of interest on the surface of the nanoparticles and the ratio,ψ, of the total electroactive surface area to the geometric area of the rotating disk surface. It is demonstrated that Koutecky-Levich analysis is applicable and yields the expected plots of I-1 versus ω-1 where I is the current and ω is the rotation speed but that the values of the electrochemical rate constants inferred are thereof koapp, not ko. Thus, for ψ 〉 1 apparent electrocatalysis might be naively but wrongly inferred whereas for ψ 〈 1 the deduced electrochemical rate constant will be less than ko. Moreover, the effect of ψ on the observed rotating disk electrode voltammograms is significant, signalling the need for care in the overly simplistic application of Koutecky-Levich analysis to modified rotating electrodes, as is commonly applied for example in the analysis of possible oxygen reduction catalysts.
文摘Plasma-synthesized cobalt oxide supported on carbon has been analyzed for its use for electrocatalytic oxygen reduction reaction （ORR） in alkaline anion exchange membrane fuel cells （AEMFC）. This work presents the ORR activity in 0.1 mol L-1 KOH and 0.1 tool L-1 K2CO3 at 25 ℃. Cyclic voltammetry （CV） was used to determine the potentials at which the ORR occurs and to evaluate the stability of catalyst. Moreover, a rotating ring-disk electrode （RRDE） was used to investigate the activity of the catalysts and the formation of the by-product hydroperoxide anion （HO2-） as well as to identify the preferred pathway of the ORR. Calculated kinetic parameters for the ORR for the cobalt catalysts are shown in this work together with a comparison to a commercial platinum catalyst. However, the cobalt oxide produced more by-products which could lead to damage of the membrane in a fuel cell through a radical attack of the polymer backbone.
基金financial support from the Department of Science and Technology of Guangdong Province,China(2019A050510043)Shenzhen Science and Technology Innovation Commission(JCYJ20180507183818040)。
文摘Zinc-air battery is one of the most promising next-generation energy conversion and storage systems.Green and low-cost catalysts with high oxygen reduction reaction(ORR)catalytic activity are desired to meet the requirements of Zinc-air batteries.Herein,poly-active centric Co3O4-CeO2/Co-N-C(ketjenblack carbon)catalysts were prepared by a facile method.The Co3O4 and CeO2 nanoparticles are uniformly anchored on the surface of Co and N doped carbon support.The half-wave potential of Co3O4-CeO2/Co-N-C in the rotating disk electrode testing is close to that of Pt/C.The Zn-air battery using Co3O4-CeO2/Co-N-C as the cathode catalyst can provide a high specific capacity of 728 mA h g^-1 at 20 mA cm^-2 and maintain a stable discharge voltage.The remarkable catalytic performance is mainly attributed to the synergistic effect among Co3O4,CeO2 and Co-N-C,the outstanding electrical conductivity and the large surface area.Benefitting from the high catalytic activity,environmental friendliness and the facile synthesis process,Co3O4-CeO2/Co-N-C catalyst lends itself well to a great prospect in the application of metalair batteries.
