Ruδ+-Engineered La2Ti2– x Ru x O7 Perovskite with Dynamic Lattice Oxygen Vacancies for Efficient and Stable Photothermal Dry Reforming of Methane

Dry reforming of methane (DRM) is a sustainable method to produce valuable syngas from two important greenhouse gases, CH4 and CO2. Traditional thermal DRM requires high temperatures, resulting in high carbon deposition, while photothermal catalysis reduces the energy barrier by using solar light and creates charge carriers. However, most of the photothermal catalysts have limited mobility of oxygen and poor charge separation, which limits the reaction kinetics. Pristine La2Ti2O7 is a layered perovskite that has a slow Ti redox activity and low oxygen-vacancy concentration, thereby restricting its catalytic activity. Ru doping at the Ti sites of La2Ti2-xRuxO7 reconstructs the electronic structure, activating the dynamic lattice oxygen exchange. This substitution leads to the generation of more oxygen vacancies and enhances the interaction of the Ru-O-Ti interface, which results in highly active sites for the activation of CH4 and CO2 molecules. In the presence of photons, pristine La2Ti2O7 generated 9.3 mmol g-1 h-1 H2 and 12.4 mmol g-1 h-1 CO. La2Ti2-xRuxO7, however, showed outstanding enhancement with production rates of 339.58 mmol g-1 h-1 H2 and 494.46 mmol g-1 h-1 CO. This is an increase of more than 35-fold and 39-fold, respectively. Mechanistic studies show that light irradiation leads to the dissociation of CO2, which maintains the oxidation of carbon-containing intermediates using activated lattice oxygen by the Mars-van Krevelen pathway. The presence of Ruδ+ species and mobile oxygen in the lattice provides continuous activation of the active sites. This redox synergy is a continuous suppression of carbon deposition, as well as provides excellent catalytic stability. It sets the framework for a promising pathway for the sustainable synthesis of syngas with high activity, selectivity, and stability.