Mo-Nitrogen nexus: Nanotechnology enhanced Mo-based nitrogen fixation towards environmental sustainability

Nitrogen (N) is an essential element for all life forms, and its availability significantly influences ecosystem productivity and biogeochemical cycles. Nitrogen fixation, the biological conversion of atmospheric nitrogen (N₂) into bioavailable forms, plays a pivotal role in N cycling and global carbon emission mitigation. Molybdenum (Mo), a transition metal and micronutrient, is a critical cofactor in the nitrogenase enzyme, and the primary catalyst of the nitrogen fixation process. Acknowledging the pivotal role of Mo in biological nitrogen fixation (BNF), extensive research has been targeted at utilizing Mo as a catalyst for commercial ammonia production. Recently, Mo-based nitrogen fertilizers have also been used for direct enhancement of the BNF in leguminous species. Both strategies hold great promise for reducing the significant negative impacts of the production and application of chemical N fertilizers, although several challenges remain. In this review, we provide a comprehensive examination of Mo-based materials/catalysts for a sustainable N economy. We will discuss the recent advances in Mo-based electrocatalysts for enhanced electrocatalytic nitrogen reduction reaction (NRR) and Mo-based nano-enabled strategies for biological nitrogen fixation, with a focus on the environmental significance of these developments. Additionally, we will discuss the efficiency and sustainability of Mo-based materials for chemical and biological nitrogen fixation.