Unlocking Efficient Near-Infrared CO₂ Photoreduction Over Metallic Photocatalysts Through Charge Polarization.

Abstract

Metallic photocatalysts provide a promising route for utilizing low-energy near-infrared (NIR) photons in CO₂ conversion because they bypass the bandgap constraints of conventional semiconductors. However, their intrinsically uniform electrostatic potential limits charge separation and CO₂ adsorption/activation, thereby restricting their photocatalytic performance. Here, we report a charge polarization strategy that addresses this bottleneck through the synergistic incorporation of sulfur vacancies (S_v) and Au single atoms (Au SAs) in metallic NiCo₂S₄. The optimized Au_SA/S_v-NiCo₂S₄ photocatalyst exhibits a 64-fold enhancement in activity relative to pristine NiCo₂S₄ under NIR irradiation without sacrificial agents, delivering CO and CH₄ production rates of 1020 and 150 µmol g^-1 h^-1, respectively. Notably, it achieves a benchmark apparent quantum efficiency (AQE) of 1.24% at 800 nm and a solar-to-chemical energy conversion (STC) efficiency of 0.86% at room temperature. Mechanistic investigations reveal that charge redistribution reshapes the photocatalytic behavior of the metallic system in two complementary ways: it induces local polarization that suppresses charge recombination, and favors the formation of bimetallic Co³⁺⋯Ni²⁺ frustrated Lewis pair (FLP) sites for CO₂ adsorption, activation, and *COOH generation. This work demonstrates charge polarization as an effective strategy for designing metallic photocatalysts, opening new opportunities for efficient solar-driven CO₂ valorization.