A considerable challenge in the conversion of carbon dioxide into useful fuels comes from the activation of CO2 to CO2 .- or other intermediates, which often requires precious-metal catalysts, high overpotentials, and/or electrolyte additives (e.g., ionic liquids). We report a microwave heating strategy for synthesizing a transition-metal chalcogenide nanostructure that efficiently catalyzes CO2 electroreduction to carbon monoxide (CO). We found that the cadmium sulfide (CdS) nanoneedle arrays exhibit an unprecedented current density of 212 mA cm-2 with 95.5±4.0 % CO Faraday efficiency at -1.2 V versus a reversible hydrogen electrode (RHE; without iR correction). Experimental and computational studies show that the high-curvature CdS nanostructured catalyst has a pronounced proximity effect which gives rise to large electric field enhancement, which can concentrate alkali-metal cations resulting in the enhanced CO2 electroreduction efficiency.
Keywords: CO2 electroreduction; cadmium sulfide; flow cells; high-curvature structures; proximity effect.
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