Ru species decoration on hierarchical Nb2O5−x modulates product selectivity for CO2 photoreduction

Abstract

Photocatalytic CO₂ reduction to CH₄ is a promising route to convert greenhouse gases into value-added fuels and chemicals. Nevertheless, achieving high efficiency and product selectivity remains a formidable challenge due to the inherent thermodynamic stability of CO₂, the complex reaction pathways and competing intermediates. Herein, hierarchical structure Nb₂O₅ thistles with oxygen vacancies (O_v) and N-doping (Nb₂O_5−x) and Ru species-decorated Nb₂O_5−x (Ru-Nb₂O_5−x) were successfully constructed for highly selective CO₂ photoreduction. Nb₂O_5−x achieves a high CO formation rate of 92.4 μmol g⁻¹ h⁻¹ with 90.4% selectivity, far beyond (≈19.6 fold) that of pristine Nb₂O₅. Notably, Ru-Nb₂O_5−x delivers a 17.0-fold higher CH₄ evolution rate (165.9 μmol g⁻¹ h⁻¹) with a CH₄ selectivity of 78.3%. Ru species (Ru⁰ and Ru^δ+) decoration triggers a selectivity switch by altering the reaction pathway to produce CH₄ instead of CO. Mechanistic studies reveal that the synergy among O_v, N-doping, and Ru sites further narrows the bandgap and modulates the electronic structure, thereby enhancing charge separation, promoting CO₂ adsorption and activation, strengthening *CO binding, and further facilitating *CH_xO formation through rapid proton extraction from water dissociation. These effects collectively suppress *CO desorption and promote *CO hydrogenation to CH₄. The present work establishes a strategic framework for designing advanced materials with controllable selectivity in CO₂ conversion.