MOFs-derived plum-blossom-like junction In/In2O3@C as an efficient nitrogen fixation photocatalyst: Insight into the active site of the In3+ around oxygen vacancy

Nitrogen activation with low-cost, visible-light-driven photocatalysts continues to be a major challenge. Since the discovery of biological nitrogen fixation, multi-component systems have achieved higher efficiency due to the synergistic effects, thus one of the challenges has been distinguishing the active sites in multi-component catalysts. In this study, we report the photocatalysts of In/In2O3@C with plume-blossom-like junction structure obtained by one-step roasting of MIL-68-In. The "branch" is carbon for supporting and protecting the structure, and the "blossom" is In/In2O3 for the activation and reduction of N2, which form an efficient photocatalyst for nitrogen fixation reaction with the performance of 51.83 μmol h-1 g-1. Experimental studies and DFT calculations revealed the active site of the catalyst for nitrogen fixation reaction is the In3+ around the oxygen vacancy in In2O3. More importantly, the elemental In forms the Schottky barrier with In2O3 in the catalyst, which can generate a built-in electric field to form charge transfer channels during the photocatalytic activity, not only broadens the light absorption range of the material, but also exhibits excellent metal conductivity.

Heterojunction photocatalysts for artificial nitrogen fixation: fundamentals, latest advances and future perspectives

As an indispensable energy source, ammonia plays an essential role in agriculture and various industries. Given that the current ammonia production is still dominated by the energy-intensive and high carbon footprint Haber-Bosch process, photocatalytic nitrogen fixation represents a low-energy consuming and sustainable approach to generate ammonia. Heterostructured photocatalysts are hybrid materials composed of semiconductor materials containing interfaces that make full use of the unique superiorities of the constituents and synergistic effects between them. These promising photocatalysts have superior performances and substantial potential in photocatalytic reduction of nitrogen. In this review, a wide spectrum of recently developed heterostructured photocatalysts for nitrogen fixation to ammonia are evaluated. The fundamentals of solar-to-ammonia conversion, basic principles of various heterojunction photocatalysts and modification strategies are systematically reviewed. Finally, a brief summary and perspectives on the ongoing challenges and directions for future development of nitrogen photofixation catalysts are also provided.