Micro-environment regulation for strong metal–support interaction in RuO₂-doped barium cerate for boosting photocatalytic ammonia production

Modulating the local microenvironment via strong metal-support interaction (SMSI) approach in Ru-based photocatalyst for improving photocatalytic ammonia production is poorly understood. Herein, we investigate the mechanism of the SMSI effect of RuO₂ on barium cerate (BC) by forming Ru-O-Ce electron transfer channel to enhance the photocatalytic ammonium (NH₄⁺) production. Among the prepared photocatalysts, BC-Ru_0.25 showed the highest NH₄⁺ formation rate of 3.533 mmol g⁻¹ h⁻¹ with a 5.464 % apparent quantum efficiency (AQE), which was 5.17-fold higher than BC. In-situ X-ray photoelectron spectroscopy (XPS) and X-ray absorption near edge structure (XANES) analyses revealed that RuO₂ doping on BC promoted the formation of Ru-O-Ce bonds and degenerate barium 3d orbitals, creating an asymmetric coordination environment that improved N₂ interaction. Additionally, the formation of a Ru-O-Ce electron channel on BC prolonged the electron decay time and improved spatial separation, resulting in higher nitric oxide (NO) radical formation due to the promotion of hydroxyl radical generation from photoexcited holes. Notably, in-situ surface-enhanced Raman spectroscopy (SERS) analysis revealed that RuO₂ loading on BC altered the electronic state of Ba owing to the SMSI effect, improved N₂ interaction on the Ba-O bonds, and facilitated the NH₄⁺ production. Density functional theory (DFT) calculations showed that RuO₂-doping of BC can result in Ba-N bonding and promote the nitric oxide reduction reaction (NORR) by reducing the energy barrier of the rate-determining step and accelerating the protonation process. This study demonstrates the SMSI effects via the strategy of a Ru-based dopant on NH₄⁺ photocatalytic production.