Synthesis Of Ni-based Catalysts And Their Electrocatalytic Performance For CO₂ Reduction

Electrocatalytic CO₂ reduction reaction（CO₂RR）could be readily integrated with renewable electricity,and convert CO₂ into high value-added chemicals.It provides a viable route towards the goal of"carbon neutrality".High-efficient catalysts are the key to CO₂RR.Among them,single-atom（SA）catalysts have been widely studied because of their high atomic utilization and tunable structures.Nickel（Ni）SA catalysts typically have high selectivities for CO in CO₂RR,but the potential window for high Faraday efficiencies for CO(FE_CO)is rather narrow and the catalytic activity needs to be improved.In this paper,a binary active site catalysts（denoted as Ni SAs-Co NCs）was designed from the atomic level and synthesized.Syngas with an almost constant H₂:CO ratio was produced over a wide potential window in CO₂RR,and was subsequently fed into thermocatalytic CO hydrogenation reactor.Furthermore,a Ni₃Te₂ dual-component catalyst was synthesized,and the FE_CO was higher than 90%over a wide potential range by tuning the two components.The detailed contents are as follows:1.Synthesis of binary active site Ni SAs-Co NCs catalyst and its performance of CO₂RR.Here,employing an in situ synthesis strategy,we constructed a self-supporting electrocatalyst featuring binary active sites.Ni SAs were in situ anchored during the growth of carbon nanotubes encapsulating Co nanocrystals（Co NCs）,resulting in a composite core–shell structure.X-ray Diffraction（XRD）showed no diffraction peaks of Ni.X-ray absorption near-edge structure（XANES）and extended X-ray absorption fine structure（EXAFS）profiles revealed the coordination structure and electron structures of Ni SAs.and Ni SAs were directly observed as a single atom in spherical differential electron microscopy.The electrocatalytic performance for CO₂RR was assessed.The binary catalyst Ni SAs-Co NCs,with its composition optimized,the Faraday efficiency of CO and H₂ can be maintained at about 35%and 65%across a broad potential window from-0.6 to-1.0 V vs.RHE.Under-0.8 V vs.RHE,the catalyst could run stably for 38 h,the current density remained basically unchanged,showing high electrochemical stability.In resulting binary catalyst,the single Ni atoms are anchored on the nanotube surface,and could give a high FE_CO over a broad potential window;the encapsulated Co nanocrystals could catalyze hydrogen evolution reaction.By optimising the ratio of the two components,precise regulation of the syngas composition is achieved.2.Synthesis of Ni₃Te₂ dual-component catalysts and its performance for CO₂RR.In this part,the metal–organic framework ZIF-8 was prepared,and Te and Ni were introduced.The Ni₃Te₂ dual-component catalysts were synthesized via pyrolysis.Transmission electron microscopy（TEM）revealed that the Ni₃Te₂ nanoparticles are uniform in size（50 nm）and loaded on a carbon support.The atomic and electronic structures were optimized by controlling the ratio of the two components.For CO₂RR,the prepared Ni₃Te₂ dual-component catalyst displayed a FE_CO above 90%over a wide potential range from-0.5 V to-1.2 V vs.RHE,and the partial current density(j _CO)of CO at-1.2 V vs.RHE was 85.4 m A cm^-2.In addition,the catalyst exhibited excellent stability with no significant declines in FE_CO and current density over 50 h continuous operation at-0.8 V vs.RHE.In this experiment,high CO selectivity over a wide potential window was achieved by optimizing the composition of the two components,which provides a new idea and method for the design and preparation of high-performance CO₂RR catalysts.