Novel pyrochlore type europium stannate - tungsten disulfide heterostructure for light driven carbon dioxide...

The reduction of carbon dioxide (CO₂) and nitrogen (N₂) to value-added products is a substantial area of research in the fields of sustainable chemistry and renewable energy that aims at reducing greenhouse gas emissions and the production of alternative fuels and chemicals. The current work deals with the synthesis of pyrochlore-type europium stannate (Eu₂Sn₂O₇: EuSnO), tungsten disulfide (WS₂:WS), and novel EuSnO/WS heterostructure by a simple and facile co-precipitation-aided hydrothermal method. Using different methods, the morphological and structural analyses of the prepared samples were characterized. It was confirmed that a heterostructure was formed between the cubic EuSnO and the layered WS. Synthesized materials were used for photocatalytic CO₂ and N₂ reduction under UV and visible light. The amount of CO and CH₄ evolved due to CO₂ reduction is high in EuSnO/WS (CO = 104, CH₄ = 64 μmol h^-1 g^-1) compared to pure EuSnO (CO = 36, CH₄ = 70 μmol h^-1 g^-1) and WS (CO = 22, CH₄ = 1.8 μmol h^-1 g^-1) under visible light. The same trend was observed even in the N₂ fixation reaction under visible light, and the amount of NH₄⁺ produced was found to be 13, 26, and 41 μmol h^-1 g^-1 in the presence of WS, EuSnO and EuSnO/WS, respectively. Enhanced light-driven activity towards CO₂ and N₂ reduction reactions in EuSnO/WS is due to the efficient charge separation through the formation of type-II heterostructure, which is in part associated with photocurrent response, photoluminescence, and electrochemical impedence spectroscopic (EIS) results. The EuSnO/WS heterostructure's exceptional stability and reusability may pique the attention of pyrochlore-based composite materials in photocatalytic energy and environmental applications.