A conformal titanyl phosphate amorphous overlayer for enhancing photoelectrochemical hydrogen peroxide production

Abstract

Photoelectrochemical (PEC) H2O2 production through water oxidation reaction (WOR) is a promising strategy, however, designing highly efficient and selective photoanode materials remains challenging due to competitive reaction pathways. Here, for highly enhanced PEC H2O2 production, we present a conformal amorphous titanyl phosphate (a-TP) overlayer on nanoparticulate TiO2 surfaces, achieved via lysozyme-molded in-situ surface reforming. The a-TP overlayer modulates surface adsorption energies for reaction intermediates, favoring WOR for H2O2 production over the competing O2 evolution reaction. Our density functional theory calculations reveal that a-TP/TiO2 exhibits a substantial energy uphill for the O* formation pathway, which disfavors O2 evolution but promotes H2O2 production. Additionally, the a-TP overlayer strengthens the built-in electric field, resulting in favorable kinetics. Consequently, a-TP/TiO2 exhibits 3.7-fold higher Faraday efficiency (FE) of 63% at 1.76 V vs. reversible hydrogen electrode (RHE) under 1 sun illumination, compared to bare TiO2 (17%), representing the highest FE among TiO2-based WOR H2O2 production systems. Employing the a-TP overlayer constitutes a promising strategy for controlling reaction pathways and achieving efficient solar-to-chemical energy conversion.(c) 2023 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by ELSEVIER B.V. and Science Press. All rights reserved.