Sequentially Regulating Potential‐Determining Step for Lowering CO2 Electroreduction Overpotential over Te‐Doped Bi Nanotips

Abstract

AbstractElectrocatalytic conversion of CO2 into formate is recognized an economically‐viable route to upgrade CO2, but requires high overpotential to realize the high selectivity owing to high energy barrier for driving the involved proton‐coupled electron transfer (PCET) processes and serious ignorance of the second PCET. Herein, we surmount the challenge through sequential regulation of the potential‐determining step (PDS) over Te‐doped Bi (TeBi) nanotips. Computational studies unravel the incorporation of Te heteroatoms alters the PDS from the first PCET to the second one by substantially lowering the formation barrier for *OCHO intermediate, and the high‐curvature nanotips induce enhanced electric field that can steer the formation of asymmetric *HCOOH. In this scenario, the thermodynamic barrier for *OCHO and *HCOOH can be sequentially decreased, thus enabling a high formate selectivity at low overpotential. Experimentally, distinct TeBi nanostructures are obtained via controlling Te content in the precursor and TeBi nanotips achieve >90 % of Faradaic efficiency for formate production over a comparatively positive potential window (−0.57 V to −1.08 V). The strong Bi−Te covalent bonds also afford a robust stability. In an optimized membrane electrode assembly device, the formate production rate at 3.2 V reaches 10.1 mmol h−1 cm−2, demonstrating great potential for practical application.