Decoding the interfacial competition between hydrogen evolution and CO2 reduction via edge-active-site modulation in photothermal catalysis

Abstract

Solar-driven photothermal catalytic CO₂ conversion with H₂O is a promising approach to produce sustainable fuels and chemicals. However, the competition between hydrogen evolution reaction (HER) and CO₂ reduction reaction (CO₂RR) results in unsatisfactory product selectivity. Noble metal nanoparticles (NMNPs) are widely used cocatalysts to introduce active sites on semiconductors, with unique active sites at the metal-semiconductor interfacial edges playing a critical role in the competitive mechanisms. Herein, we prepared a series of NMNPs loaded on Al-doped SrTiO₃ with abundant interfacial edge sites for continuous photothermal catalytic CO₂ and H₂O conversion. Different NMNPs demonstrated distinct CO₂-induced effects on hydrogen evolution. The key intermediate interactions were investigated by in situ diffuse reflectance infrared Fourier-transform spectroscopy (DRIFTS) and density functional theory (DFT) calculations. The results revealed that bidentate carbonate (b-CO₃²⁻) tended to occupy the edge sites at the metal-semiconductor interfaces, competitively consuming the active sites for ∗H adsorption and altering the energy barrier of hydrogen evolution. The predominant site-blocking effect of b-CO₃²⁻ on Rh-loaded catalysts was verified through establishing a simplified geometric model to quantify the correlation of particle sizes, active site proportions and CO₂-induced hydrogen production variations. Controlling Rh nanoparticle size can tune the proportion of edge sites, which involves a trade-off between ∗H coverage and CO₂ activation and promotes the CO₂RR process toward methane production. This work initially unravels the interfacial competitive mechanism between HER and CO₂RR via edge-active-site modulation, hoping to provide valuable insights for the rational catalyst design and offer potential strategies to enhance CO₂ conversion efficiency.