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

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.