Enhanced Lewis acid-base synergistic photocatalyst for selective benzimidazole synthesis coupled with hydrogen evolution

Developing photocatalytic systems capable of simultaneously synthesizing value-added heterocycles and producing green hydrogen is of great importance for solar-driven chemical transformations and sustainable manufacturing. In this work, we report a highly efficient bifunctional photocatalyst composed of Au 4 Pd 5 alloy nanoparticles anchored on nitrogen-doped TiO 2 (N-TiO 2-x ), wherein the reinforced Pd Lewis acidic (LA) sites and reinforced O Lewis basic (LB) sites synergistically activate o-phenylenediamine (OPD) and ethanol, respectively. This cooperative interaction facilitates a single-intermediate pathway (ethanol - ethoxy radical - acetaldehyde), leading to the selective formation of 2-methylbenzimidazole (2MBZ) and concurrent H 2 evolution. Under optimal conditions, the system achieves a 2MBZ yield of 3.80 mmol·g −1 ·h −1 , H 2 generation rate of 14.17 mmol·g −1 ·h −1 , and a selectivity of 94.43 %, outperforming all previously reported photocatalytic systems to date. Mechanistic insights derived from in-situ characterizations, and density functional theory (DFT) calculations reveal that electron redistribution at the Au-Pd interface and oxygen vacancy (O v ) induced charge modulation in N-TiO 2-x are responsible for the enhanced charge separation, reactant adsorption, and activation. The system maintains excellent performance under natural sunlight, with H 2 and 2MBZ production rates of 11.96 and 3.11 mmol·g −1 ·h −1 , respectively, which will be more economical than the conventional thermal route and demonstrating strong scalability.