Rational design of metal-single-atom decorated CaTaO2N as multifunctional photocatalysts for water splitting and CO2 reduction

Abstract

Perovskite oxynitrides, exemplified by CaTaO2N, have emerged as promising visible-light photocatalysts for solar fuel generation, including overall water splitting and CO2 reduction. Loading cocatalysts is a proven strategy to enhance performance, yet the systematic design of highly dispersed metal cocatalysts with tailored multi-functionality remains underexplored. Herein, we employ first-principles density functional theory (DFT) calculations to systematically screen twelve single metal atoms (M = Fe, Co, Ni, Cu, Ru, Rh, Pd, Ag, Os, Ir, Pt, Au) anchored on the CaTaO2N(010) surface as single-atom cocatalysts for the hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and CO2 reduction reaction (CO2RR). Our calculations reveal distinct catalytic functionalities governed by the electronic structure of the metal adatoms. We identify several high-performance candidates based on activity descriptor: The Fe-, Cu-, Rh-, Ag-, and Os-adsorbed systems exhibit ΔG H* values superior to the benchmark Pt-adsorbed system, indicating their potential as efficient and cost-effective HER catalysts; Au-modified surface exhibits a relatively lower theoretical overpotential for the OER, identifying it as an effective OER catalyst; Rh-decorated surface shows outstanding activity for both HER and OER; most notably, Co-, Ni-, and Pd-decorated systems exhibit superior and balanced activities for HER, OER, and CO 2 RR, making them exceptional candidates for integrated solar fuel production systems that couple water splitting with CO 2 conversion. Mechanistic analysis elucidates the origin of selectivity, linking it to the metal-dependent binding strengths of key reaction intermediates and the modulated charge transfer at the metalsupport interface. This work not only provides a library of efficient single-atom cocatalysts for CaTaO 2 N but also establishes a design principle for developing multifunctional, noble-metal-free photocatalytic systems for sustainable energy applications.