Anchored atomic tungsten on a B40 cage: a highly active and selective single-atom catalyst for nitrogen reduction

Design of Single-Atom Catalysts for E lectrocatalytic Nitrogen Fixation

The Electrochemical nitrogen reduction reaction (ENRR) can be used to solve environmental problems as well as energy shortage. However, ENRR still faces the problems of low NH3 yield and low selectivity. The NH3 yield and selectivity in ENRR are affected by multiple factors such as electrolytic cells, electrolytes, and catalysts, etc. Among these catalysts are at the core of ENRR research. Single-atom catalysts (SACs) with intrinsic activity have become an emerging technology for numerous energy regeneration, including ENRR. In particular, regulating the microenvironment of SACs (hydrogen evolution reaction inhibition, carrier engineering, metal-carrier interaction, etc.) can break through the limitation of intrinsic activity of SACs. Therefore, this Review first introduces the basic principles of NRR and outlines the key factors affecting ENRR. Then a comprehensive summary is given of the progress of SACs (precious metals, non-precious metals, non-metallic) and diatomic catalysts (DACs) in ENRR. The impact of SACs microenvironmental regulation on ENRR is highlighted. Finally, further research directions for SACs in ENRR are discussed.

Tungsten-Based Nanocatalysts: Research Progress and Future Prospects

The high price of noble metal resources limits its commercial application and stimulates the potential for developing new catalysts that can replace noble metal catalysts. Tungsten-based catalysts have become the most important substitutes for noble metal catalysts because of their rich resources, friendly environment, rich valence and better adsorption enthalpy. However, some challenges still hinder the development of tungsten-based catalysts, such as limited catalytic activity, instability, difficult recovery, and so on. At present, the focus of tungsten-based catalyst research is to develop a satisfactory material with high catalytic performance, excellent stability and green environmental protection, mainly including tungsten atomic catalysts, tungsten metal nanocatalysts, tungsten-based compound nanocatalysts, and so on. In this work, we first present the research status of these tungsten-based catalysts with different sizes, existing forms, and chemical compositions, and further provide a basis for future perspectives on tungsten-based catalysts.

Nitrogen reduction reaction on single cluster catalysts of defective PC6-trimeric or tetrameric transition metal

The traditional Haber-Bosch method of ammonia (NH₃) synthesis has low production efficiency and can lead to greenhouse gas emission due to high temperature and pressure dependent reactions. Hence, the nitrogen reduction reaction (NRR) in a mild environment has been developed. However, the inert NN triple bond and the competition with the hydrogen evolution reaction (HER) limit its wide application. In order to find an effective way of reducing N₂ into NH₃, in this work, PC₆ monolayers with good electro-optical properties and eight transition metals (V, Cr, Mn, Fe, Co, Ni, Cu, Zn) are chosen to construct PC₆-TM₃ and PC₆-TM₄ single cluster catalysts (SCCs), which are proved to have low overpotential, multiple active-sites and superior activity. The thermodynamic stability, N₂ adsorption, reaction paths, selectivity for the NRR and catalytic mechanism are systematically investigated. (PC₆-Co₃, PC₆-Fe₄)/(PC₆-V₃, PC₆-Cr₃)/(PC₆-V₄, PC₆-Mn₄) prefer to adsorb N₂ rather than H in the end-on/side-on I/side-on III mode. PC₆-Fe₄ and PC₆-Cr₃ are finally screened out which have excellent catalytic activity with an overpotential of -0.46 V and -0.26 V in the consecutive path of side-on III and I modes, respectively. Moreover, both of them have 100% faradaic efficiency and present high selectivity for the NRR. The catalytic mechanism is elucidated by discussing the electronic properties of PC₆-Cr₃, where the back-donation behaviors of Cr atoms play an important role during the formation of NH₃. This research may provide theoretical guidance for finding potential NRR catalysts with excellent performance and high selectivity.