Na-Ru bimetallic functional sites promote photo-driven CO₂ directed conversion into CH₄

Recently, there has been a significant increase in interest in using photocatalysis for the energy conversion of polluting gases. In this research, sodium and ruthenium bimetallic functional sites co-modified bismuth tungstate (Ru/Na-Bi₂WO₆) nanoflower photocatalyst was synthesized via the hydrothermal method. The CO₂ reduction products on the Bi₂WO₆ substrate were CO (1.66 μmol/g/h, 68 %) and CH₄ (0.78 μmol/g/h, 32 %). After optimization, a significant change in the CO₂ products of the Bi₂WO₆-based composite material was observed, with CO (0.61 μmol/g/h, 3.6 %) and CH₄ (16.1 μmol/g/h, 96.4 %). Results showed that the dominance of CH₄ as the main product in the Ru/Na-BWO system is attributed to the effective doping of Na, which generates impurity energy levels composed of oxygen vacancies, lowering the conduction band position of Bi₂WO₆, thereby suppressing CO generation, and enhancing CH₄ selectivity by changing the CO₂ activation pathway. The remarkable performance is ascribed to the synergized adsorption and activation of CO₂ by the tandem Na⁺ sites and Ru⁰ sites. Specifically, the doped Na⁺ sites play a major role in promoting the adsorption CO₂ molecules, while the Ru⁰ sites play a dominant role in facilitating the activation of the intermediates.