Layered bismuth oxide/bismuth sulfide supported on carrageenan derived carbon for efficient carbon dioxide electroreduction to formate

Electrochemical reduction of carbon dioxide(CO_(2)ER)into formate plays a crucial role in CO_(2)conversion and utilization.However,it still faces the problems of high overpotential and poor catalytic stability.Herein,we report a hybrid CO_(2)ER electrocatalyst composed of layered bismuth sulfide(Bi_(2)S_(3))and bismuth oxide(Bi_(2)O_(3))supported on carrageenan derived carbon(Bi-CDC)prepared by a combined pyrolysis with hydrothermal treatment.In such 3 D hybrid,layered Bi_(2)O_(3)and Bi_(2)S_(3)are uniformly grown on nanocarbon supports.Benefiting from strong synergistic effect between Bi_(2)O_(3)/Bi_(2)S_(3)and nanocarbon,Bi-CDC-1:2 displays a high Faradic efficiency(FE)of>80%for formate production in the range of-0.9 V to-1.1 V with the maximum formate FE of 85.6%and current density of 14.1 mA·cm^(-2) at-1.0 V.Further,a positive onset potential of-0.5 V,a low Tafel slope of 112.38 mV·dec^(-1),and a slight performance loss during long-term CO_(2)ER tests are observed on Bi-CDC-1:2.Experimental results shows that the better CO_(2)ER performance of Bi-CDC-1:2 than that of Bi_(2)O_(3)can be attributed to the strong interfacial interactions between nanocarbons and Bi_(2)O_(3)/Bi_(2)S_(3).In situ ATR-FTIR measurements reveal that the rate-determining step in the CO_(2)ER is the formation of HCOO^(*) intermediated.Compared with carbon support,Bi-CDC-1:2 can promote the production of HCOO^(*) intermediate and thus promoting CO_(2)ER kinetic.

Spin polarization strategy to deploy proton resource over atomic-level metal sites for highly selective CO_(2) electrolysis

Unlocking of the extremely inert C=O bond during electrochemical CO_(2) reduction demands subtle regulation on a key“resource”,protons,necessary for intermediate conversion but also readily trapped in water splitting,which is still challenging for developing efficient single-atom catalysts limited by their structural simplicity usually incompetent to handle this task.Incorporation of extra functional units should be viable.Herein,a proton deployment strategy is demonstrated via“atomic and nanostructured iron(A/N-Fe)pairs”,comprising atomically dispersed iron active centers spin-polarized by nanostructured iron carbide ferromagnets,to boost the critical protonation steps.The as-designed catalyst displays a broad window(300 mV)for CO selectivity>90%(98%maximum),even outperforming numerous cutting-edge M–N–C systems.The well-placed control of proton dynamics by A/N-Fe can promote*COOH/*CO formation and simultaneously suppress H2 evolution,benefiting from the magnetic-proximity-induced exchange splitting(spin polarization)that properly adjusts energy levels of the Fe sites’d-shells,and further those of the adsorbed intermediates’antibonding molecular orbitals.