Non-noble Metal Based Nanoelectrocatalysts:Structure Design,Synthesis,and Electrocatalytic Performance

Due to the rapid consumption of fossil fuels,energy shortages and environmental problems become increasingly serious.The carbon dioxide has caused serious climate problems such as global warming.There are two main strategies to solve the above problems:one is to recover carbon dioxide from the atmosphere and convert it into beneficial chemicals(carbon recovery);the other is to use clean energy to replace fossil fuels to reduce carbon dioxide emissions(carbon reduction).Carbon dioxide electroreduction reaction(CO2RR)can use renewable electricity to convert carbon dioxide into high value-added carbon-based fuels,while hydrogen fuel cells can directly use green hydrogen as fuel to convert the chemical energy contained in hydrogen into electrical energy without carbon dioxide emissions.However,the current CO2RR process and the hydrogen oxidation reaction(HOR)at the anode side of hydrogen fuel cells still face the problems of high catalyst cost,poor catalytic activity,selectivity and stability.Electrocatalysts based on non-noble metal materials can effectively reduce the cost,but generally face challenges such as suboptimal electronic structure and unstable structure.Therefore,how to control the structure of non-noble metal materials at the nanoscale to improve the catalytic performance is the core scientific problem to be solved in this field.1.A series of cadmium sulfide nanoelectrocatalysts(nanotips,nanorods,and nanoparticles)with different morphologies were prepared using microwave synthesis methods,among which the cadmium sulfide nano-tip catalysts have tip curvature radii as low as 3 nm.Due to the remarkable point discharge phenomenon of the nano-tips and the "proximity effect" between the tips,the electric field near the high-curvature nano-tip cadmium sulfide catalyst can be increased more than 10 times,and the enhanced electric field leads to the enrichment of potassium ions in the electrolyte on the catalyst surface.Potassium ions can shorten the Cd-C bond from 2.37 (?) to 2.25 (?)through non-covalent interaction,which promotes the adsorption of carbon dioxide molecules by the catalyst and reduces the reaction energy barrier for carbon monoxide generation.The experimental results show that the cadmium sulfide nanotips exhibit superior carbon monoxide generation efficiency compared to the nanorod and nanoparticle catalysts:in flow cell,an industrial-grade current density of 212 mA cm-2 is obtained,and the Faradaic efficiency of carbon monoxide is as high as 95.5%,which is the highest performance of similar non-noble metal catalysts.And due to the relatively negative theoretical reduction potential of cadmium sulfide(-1.17 V relative to the standard hydrogen electrode),the nano-tip cadmium sulfide catalyst exhibited excellent electrochemical stability in the CO2RR process.This study provides a new idea for the morphology regulation and performance improvement of non-noble metal catalysts in CO2RR process.2.Cuprous oxide polyhedra(cube,octahedron,and dodecahedron)exposing different crystal planes were designed and prepared as precursor catalysts for CO2RR.The cuprous oxide polyhedra can transform into pure copper catalysts with exposed(100),(110)and(111)facets during the CO2RR process.Theoretical calculation results reveal that the Cu(100)crystal face has the best adsorption energy of*CO intermediates,which is more favorable for the*CO-CO dimerization reaction,and has the highest reactivity of CO2RR to generate multi-carbon products.However,the surface energy of the Cu(100)is high,and it faces the problem of poor stability in the CO2RR process.The calculation and analysis of the catalyst surface covered with different amounts of CO2RR intermediates showed that increasing the coverage of*CO intermediates on the surface can significantly reduce the surface energy of the Cu(100).The experimental results in the flow cell show that the cubic cuprous oxide precursor catalyst has a Faradaic efficiency of up to 75.5%for the multi-carbon product,and the partial current density of the multi-carbon product is about-217 mA cm-2 with negligible decay.This crystal plane regulation strategy provides a new idea for the development of catalysts with high activity and high stability.3.A series of Ni-Mo-Nb metallic glass catalysts(Ni72Mo8Nb20,Ni57Mo8Nb35,Ni52Mo13Nb35,and Ni47Mo18Nb35)with different compositions and amorphous structures were prepared by the melt spinning method.By adjusting the short-range and medium-range atomic structures of the amorphous catalyst,the Ni52Mo13Nb35 sample obtained optimized H and H2O adsorption energy.The HOR catalytic intrinsic activity of the Ni52Mo13Nb35 sample under alkaline conditions is comparable to commercial Pt.Compared with traditional crystalline alloy catalysts,the metal glass catalyst with the lack of crystal defects that would serve as galvanic cells to initiate local corrosion,which endows the metal glass with an oxidation resistance potential of up to 0.8 V.It is the material with the best oxidation resistance among non-noble metal catalysts.The metal glass catalyst also exhibits a peak power density of 390 mW cm-2 in fuel cell,which is the best performance of current non-noble metal materials.The novel strategy provides a new idea for the design of non-noble metal catalysts with high HOR performance under alkaline conditions.