Design of novel transition metal doped pyrazine-modified graphyne as highly effective electrocatalysts for nitrogen fixation

Abstract

The production of ammonia consumes plenty of energy every year, so it is crucial to develop efficient and sustainable methods of electrocatalytic ammonia synthesis. Although some materials have shown high catalytic activity for nitrogen reduction reaction (NRR), searching for catalytic materials with excellent electrical properties is still a promising topic. Graphyne and its family are well suited as catalysts due to their high electrical conductivity and carrier mobility. In this paper, we have systematically studied the catalytic properties of transition metal atoms anchored on pyrazine-modified graphyne (pyGY) for NRR by density functional theory calculations. Through a series of scanning procedures, Nb, Mo and W-pyGYs are found to be excellent catalysts for electrocatalytic NRR with limiting potentials of − 0.43 V, − 0.36 V, and − 0.46 V, respectively. Moreover, solvation effects are considered and the lowering effect of solvent on the limiting potential is revealed. In addition, the mechanism of superior catalytic activity is explored from an electronic perspective. Finally, two descriptors related to electronegativity and valence electron number are selected to clarify the trend of NRR activity. The volcano diagram trends of NN bond length, Gibbs free energy change in the first hydrogenation step and limiting potential are revealed. This work provides a reliable method for screening efficient electrocatalytic nitrogen fixation catalysts.