Effect of Synthesis Method on Reaction Mechanism for Hydrogen Evolution over CuxOy/TiO2 Photocatalysts: A Kinetic Analysis

Abstract

The existing literature survey reports rare and conflicting studies on the effect of the preparation method of metal-based semiconductor photocatalysts on structural/morphological features, electronic properties, and kinetics regulating the photocatalytic H2 generation reaction. In this investigation, we compare the different copper/titania-based photocatalysts for H2 generation synthesized via distinct methods (i.e., photodeposition and impregnation). Our study aims to establish a stringent correlation between physicochemical/electronic properties and photocatalytic performances for H2 generation based on material characterization and kinetic modeling of the experimental outcomes. Estimating unknown kinetic parameters, such as charge recombination rate and quantum yield, suggests a mechanism regulating charge carrier lifetime depending on copper distribution on the TiO2 surface. We demonstrate that H2 generation photoefficiency recorded over impregnated CuxOy/TiO2 is related to an even distribution of Cu(0)/Cu(I) on TiO2, and the formation of an Ohmic junction concertedly extended charge carrier lifetime and separation. The outcomes of the kinetic analysis and the related modeling investigation underpin photocatalyst physicochemical and electronic properties. Overall, the present study lays the groundwork for the future design of metal-based semiconductor photocatalysts with high photoefficiencies for H2 evolution.