Nb-induced intermediate species modulation on BiOBr for overcoming the rate-determining step in photocatalytic CO2 reduction

Nb-doped BiOBr photocatalyst was synthesized via a facile method. • Nb-BiOBr exhibits significantly enhanced CO selectivity and production rate. • Nb-induced impurity levels enhance light absorption and prolong carrier lifetimes. • Nb doping lowers the rate-determining barrier for CO 2 photoreduction on BiOBr. Photocatalytic CO 2 reduction using water as a proton source offers a sustainable and promising route for renewable fuel production, yet its efficiency is limited by poor internal charge separation and sluggish surface reaction kinetics of photocatalysts. Bismuth oxybromide has attracted attention due to its favorable structure, but it suffers from rapid photo-generated charge recombination and low surface reactivity. In this work, Nb-doped BiOBr (Nb-BiOBr) nanosheets were successfully fabricated via a facile hydrothermal method. The incorporation of Nb atoms into the BiOBr lattice introduces impurity energy levels within the band structure, which broadens visible-light absorption and prolongs the average lifetime of charge carriers. As a result, the optimized Nb-BiOBr achieves a high CO production rate of 20.68 μmol g –1 h −1 , which is 4.3 times that of the undoped BiOBr. Density functional theory calculations reveal that Nb doping effectively modulates the adsorption and evolution of reaction intermediate. The Gibbs free energy change (Δ G ) of the critical *CO 2 to *COOH conversion step is reduced from 0.89 eV to 0.54 eV (vs. SHE). This work demonstrates that the strategic metal doping can overcome kinetic limitations by tailoring intermediate adsorption, providing a viable design strategy for high-performance photocatalysts for CO 2 conversion. The introduction of Nb-induced impurity levels endowed the BiOBr photocatalyst with high CO selectivity and production rate in CO 2 photoreduction. Download: Download high-res image (122KB) Download: Download full-size image