Mesoporous bismuth nanosheets electrochemically transformed from facet-controlled bismuth oxyiodide for selective electrocatalytic reduction of CO2 to formic acid.

Abstract

Mesoporous bismuth nanosheets are achieved via electrochemical transformation from (100)-facet exposed BiOI. Theoretical modelling and calculations simulate the in situ morphological variation of BiOI-to-Bi. Mesoporous Bi nanosheets show superior electrochemical CO2 reduction performance which can rapidly reach a faradaic efficiency for formic acid (HCOOH) of 95.9% at -0.77 VRHE, compared to smooth Bi nanosheets with maximum faradaic efficiency of 93.8% at -0.87 VRHE. In conjunction with Tafel analysis and DFT results, the electrochemical CO2 reduction on mesoporous Bi nanosheets is kinetically faster twith more resistance to H2 generation than that of smooth Bi-001 nanosheets. The CO2-to-HCOOH pathway for on (012) and (001) planes of Bi is both preferred via *OCHO intermediate. The mesoporous structure induced more accessible interaction with CO2 makes predominant contributions to the enhanced performance rather than subsequent CO2 activation on different facets of Bi.