Design And Preparation Of Bismuth-based Nanomaterials And Investigation Of Their Performance For Electrocatalytic Carbon Dioxide Reduction

The electrochemical carbon dioxide reduction reaction(CO2RR),which converts CO2 into energy-intensive chemicals or fuels driven by renewable energy,has attracted wide attention in academia as a potential solution to achieve environmental and energy sustainability.Among the various products of electrocatalytic CO2RR,formate(formic acid)is considered to be one of the highest value-added products.In terms of market income,the economic value of formic acid is much higher than other major products such as methanol and methane.In addition,it is widely used in pesticide,dyeing,textile and other industries.However,the electrochemical CO2RR is currently facing many challenges,such as low energy efficiency,high overpotential and poor selectivity.Therefore,in order to achieve large-scale application of CO2RR,it is very necessary to develop electrocatalysts for formate production with excellent activity and high selectivity.In this paper,we designed and synthesized a green and feasible Bi-based electrocatalysts for CO2 conversion with low cost and high electrocatalytic performance,and systematically explored the electrocatalytic performance and application prospect of such catalyst in the CO2RR process.The main research contents of this paper are as follows:Bi2O3 nanosheets(NSs)were synthesized by hydrothermal reaction,and Sn nanoparticles were uniformly electrodeposited on the surface of Bi2O3 NSs to form Sn-Bi2O3 NSs electrocatalysts,which exhibited excellent electrocatalytic performance for the selective of CO2 reduction to formate.The results show that the Sn-Bi2O3 NSs catalyst for the production of formate can achieve a high faradaic efficiency(FE)of 95.12%and partial formate current density of 28.19 mA/cm2 at-1.0 V(vs.RHE).The Sn-Bi2O3 NSs exposed a large number of edge active sites,which facilitated the mass transport of CO2 and HCOO-during the reaction,thus favoring high formate current densities.Furthermore,the interface of Sn nanoparticles with Bi2O3 NSs facilitated bimetallic interactions and enhanced the adsorption and activation of CO2 and ultimately achieving the selectivity of CO2RR for high formate production.The synergistic effect of Sn and Bi components and the unique topographic effect finally achieve high formate current density and high formate selectivity.Bimetallic BixIny(x,y is percentage composition)nanoparticle(NPs)electrocatalyst was successfully prepared by a simple one-step synthesis method.By changing the Bi/In mole ratio,changing the amount of surfactant PVP and solvent DMF,regulating the surface morphology of BixIny catalysts,improving the conversion of CO2 to formate FE.In the electrochemical performance test,Bi88.77in11.23 NPs is the most favorable for formate formation and the FE of formate can reached 94.29%at-1.0 V(vs.RHE).Based on the synergistic effect of adsorption of favorable intermediates and binary metal surface,the intrinsic electronic structure of Bi metal was reconstructed by introducing In atoms,and the selectivity of CO2 to formate was improved.Based on the obtained Bi88.77In11.23 NPs,a CO2RR‖OER(oxygen evolution reaction)full-cell system was further constructed,and the polarization curve showed good electrocatalytic performance,which could reach 10 mA/cm2 at the decomposition voltage of 3.4 V.Meanwhile,the current density can reach 6.68 mA/cm2 at 3.0 V.In this study,a series of bimetallic Bi-Sb(x)/CP were prepared on carbon paper(CP)substrates by electrodeposition.The synergistic effect of Bi and Sb components and the unique self-supporting electrode lead to high formate selectivity and excellent stability.The results show that the selectivity of formate was 88.30%at-0.9 V vs.RHE.In addition,the bimetal Bi-Sb/CP catalyst with nanosheet structure has a good durability of 25 h.DFT calculations showed that Bi(012)-Sb reduced the adsorption energy of the*OCHO intermediate and promoted the mass transfer of charges.The optimally adsorbed*OCHO intermediate promotes formate production while inhibiting the CO-producing pathway.Finally,we also optimize the CO2RR activity by flow-cell.The bimetallic Bi-Sb catalyst was stabilized at a current density of 160 mA/cm2 at a potential of-1.2 V(vs.RHE),and the average selectivity of the catalyst was about 81.30%and showed excellent stability for 40 h.