1D α-Fe₂O₃/ZnO Junction Arrays Modified by Bi as Photocathode: High Efficiency in Photoelectrochemical Reduction of CO₂ to HCOOH

Abstract

Photoelectrocatalytic (PEC) CO₂ reduction to value-added chemicals is a promising solution to address the energy and environmental issues we face currently. Herein, a unique photocathode Bi@ZFO NTs (Bi and α-Fe₂O₃ co-modified ZnO nanorod arrays) with high utilization of visible light and sharp-tips effect are successfully prepared using a facile method. Impressively, the performance of Bi@ZFO NTs for PEC CO₂ reduction to HCOOH included small onset potential (-0.53 V vs RHE), Tafel slope (101.2 mV dec^-1), and a high faraday efficiency of 61.2% at -0.65 V vs RHE as well as favorable stability over 4 h in an aqueous system under visible light illumination. Also, a series of experiments were performed to investigate the origin of its high activity, indicating that the metallic Bi and α-Fe₂O₃/ZnO nanojunction should be responsible for the favorable CO₂ adsorption/activation and charge transition/carrier separation, respectively. Density functional theory calculations reveal that the Bi@ZFO NTs could lower the intermediates' energy barrier of HCOO* and HCOOH* to form HCOOH due to the strong interaction of Bi and α-Fe₂O₃/ZnO.