Novel two-dimensional molybdenene as a promising electrocatalyst for the nitrogen reduction reaction: a first-principles prediction

The exploration of two-dimensional (2D) metallenes is driven by their noteworthy attributes, encompassing high conductivity and substantial exposure of metal active sites, facilitating the development of nitrogen reduction reaction (NRR) electrocatalysts characterized by a low overpotential and superior selectivity. Here, employing first-principles swarm-intelligence structural search methods, we predict molybdenene as a novel and stable non-precious metallene, featuring a 2-atom-thick structure. Our findings demonstrate that the basal plane of molybdenene showcases remarkable catalytic activity with an overpotential of 0.27 V. Bader charge analysis reveals that the exposed Mo bonded to N_<i>x</i>H_<i>y</i> groups not only transfers electrons to these groups but also the remaining Mo transfers electrons to N_<i>x</i>H_<i>y</i> upon the breaking of NN bonds. This electron transfer mechanism contributes to elevated NRR catalytic activity. Our work broadens the scope of metallenes as promising electrocatalysts for the NRR with the expectation that more attention will be paid to emerging metallenes, thus offering a modest contribution to the theoretical exploration, fundamental understanding and practical application of metallenes.