Chemical reconstruction of orthorhombic Bi₅O₇I to well-aligned array of (BiO)₂CO₃ nanosheets, selectively exposing the CO₃ ²⁻ moiety at the edge side was demonstrated. This significantly improved the catalytic efficiency for CO₂-to-formate conversion to 100 % Faradaic efficiency in a low overpotential region.

Abstract

Chemical reconstruction of bismuth oxyiodides using bicarbonates is tried to selectively grow (BiO)₂CO₃ edge side. Orthorhombic o-Bi₅O₇I undergoes a total reconstruction process by its phase transformation into tetragonal (BiO)₂CO₃ (BOC-o) to form a well-aligned nanosheet array with maximally exposing CO₃ ²⁻ moiety at the edge side. The post-reconstruction BOC-o catalyst achieved 100 % Faradaic efficiency at −0.86 V vs. RHE for CO₂-to-formate conversion. However, another conservative reconstruction of tetragonal t-BiOI into tetragonal (BiO)₂CO₃ (BOC-t) exposed majorly a less reactive [BiO]⁺ layer. At low overpotential regions, the catalytic cycle of BOC-o begins with the initial conversion of the CO₃ ²⁻ moiety into formate at the [−OBi−(CO₃)−BiO−] site, but at high overpotential regions, the [BiO]⁺ layer undergoes reduction to metallic Bi and multi-catalytic species proceed with CO₂ reduction. Otherwise, the deactivation of Bi⁺ site by an organic molecule switched on another catalysis of proton reduction, preventing CO₂ reduction.