An overview on noble metal (Group VIII)-based heterogeneous electro-catalysts for the nitrogen reduction reaction.

The typical Haber-Bosch method of nitrogen (N 2 ) reduction to ammonia (NH 3 ) production, expends a lot of energy, resulting in severe environmental issues. Electro-catalytic N 2 reduction to NH 3 formation by renewable resources is one of the effective ways to settle the issue. However, the electro-catalytic performances and selectivity of catalysts for electrochemical nitrogen reduction reaction (NRR) are very low. Therefore, it is of great significance to develop more efficient electro-catalysts to satisfy the needs of the practical use. Among the reported catalysts, those based on Group VIII noble metals heterogeneous catalysts display excellent NRR activities and high selectivity because of their good conductivity, rich active surface area, unfilled d-orbitals, and the abilities with easy adsorption of reactants and stable reaction intermediates. Herein, we will introduce the progress of Group VIII precious metals heterogeneous catalysts applied in the electrocatalytic N 2 reduction reaction. Then single precious metal electrocatalysts, precious metal alloy electrocatalysts, heterojunction structure electrocatalysts, and precious metal compounds based on the strategies of morphology engineering, crystal facet engineering, defect engineering, heteroatom doping, and synergetic interface engineering will be discussed. Finally, the challenges and prospects of the NH 3 synthesis have been put forward. In the review, we will provide helpful direction to the development of efficient electro-catalysts for catalytic N 2 reduction reaction.