Oxygen regulates the interfacial charge transfer rate at the semiconductor–promoter interface to promote the selective oxidation of anhydrous methanol

Abstract

In the field of photoelectrocatalysis, the interfacial charge transfer rate at the semiconductor/solvent interface is a key factor restricting the efficiency of selective oxidation of anhydrous methanol and the selectivity of products. This study focuses on the effect of a regulatory mechanism of oxygen and a metal co-catalyst on the interfacial charge transfer kinetics. Through theoretical modeling and experimental verification, the influence of these factors on the photoelectrocatalytic reaction pathways is revealed. Current density and charge transfer rate models for the semiconductor–solvent interface and the semiconductor–metal promoter–solvent interface regulated by oxygen have been constructed, and a multi-interfacial charge coupling model has been established. The presence of oxygen significantly enhances the interfacial charge transfer rate at the semiconductor–metal promoter–solvent interface. Under a bias of 1.0 V vs. Ag/AgCl, the maximum net interfacial charge transfer rate increases from 2.2 × 10⁻¹⁷ cm⁴ s⁻¹ in an argon atmosphere to 4.1 × 10⁻¹⁷ cm⁴ s⁻¹ in an oxygen atmosphere, representing an 86.7% increase in the interfacial charge transfer rate. At the same time, the synergy between the metal promoter and oxygen reduces the time scale of interfacial charge transfer, accelerating the migration of photogenerated electrons. By adjusting the proportion of oxygen in the photocatalytic reaction, the selectivity of the oxidation products of anhydrous methanol can be regulated. Under oxygen-free conditions, the selectivity of formaldehyde is nearly 100%. When the oxygen flow rate accounts for 10%, the rate of the hydrogen evolution reaction reaches a maximum of 119.43 μmol h⁻¹, and the catalyst exhibits excellent stability. This study provides both theoretical and experimental bases for improving the interfacial charge separation efficiency in photoelectrocatalytic systems. Meanwhile, it also has a certain reference value for the design of catalysts for efficient energy conversion and selective synthesis.