Curved Surface Boosts Electrochemical CO₂ Reduction to Formate via Bismuth Nanotubes in a Wide Potential Window

Abstract

Electrochemical CO2 reduction reaction (CO2RR) to formate is considered as one of the most promising routes for value-added fuels and chemical productions. The achievement of excellent activity and high Faradaic efficiency in a wide potential range is critical for mature applications. To this regard, we first employed density functional theory simulations to predict activity of Bi nanotubes and Bi nanosheets to CO2RR and selectivity toward formate. The theoretical thermodynamic analysis of the reaction energetics suggests that the limiting potential for CO2 reduction to HCOOH decreases with the increase of the curvature, suggesting a wider potential window of Bi nanotubes for formate formation. Then, Bi nanotubes with highly curved surface were experimentally prepared, showing a large current density (−39.4 mA cm–2 at −1.1 V vs reversible hydrogen electrode (RHE)) for CO2 reduction and a maximum formate selectivity of 97% at −1.0 V vs RHE. More importantly, compared with Bi nanosheets, an appreciable selectivity for formate was achieved on Bi nanotubes in a significantly wider potential window of ∼600 mV (selectivity > 80%). This research provides not only the CO2RR activity–surface structure relationship of metallic Bi but also an efficient strategy for the rational design of electrocatalysts with high activity and selectivity in a wide potential window for CO2RR, which is favorable for compatible application with varied types of photovoltaics and other renewable energy sources.