Single Vanadium Atom Achored on Sulfur-Doped Graphene as an Efficient Electrocatalyst toward the Nitrogen Reduction Reaction: A Computational View

The sustainable synthesis of ammonia via the direct reduction of nitrogen is expected to be achieved by the electrochemical nitrogen reduction reaction (NRR) method; continuous efforts have been devoted to the search for excellent NRR catalysts. Herein, inspired by a few recent works, we performed a comprehensive first-principles calculation on eight vanadium (V)-anchored sulfur (S)-doped graphene catalysts (V-SxCNc-x@Gr) to study their NRR catalytic performance. V-S2C@Gr exhibits superior activity with extremely high limiting potential (U-L) of -0.17 V, outstanding thermodynamic/electrochemical stabilities, and good selectivity. Surprisingly, V-S-3@Gr is even better than V-S2C@Gr. On V-S-3@Gr, the NRR is an exothermic process with continuously decreasing Gibbs free energy. The NRR can spontaneously occur on it without an externally applied potential. We also found that doping more S in the coordination environment of V leads to more charges accumulating around V, thus improving the more effective activation of the NN bond and, finally, higher U-L. It is worth trying the V/S combination on other substrates and more excellent NRR catalysts are expected to be found, this work can provide certain reference basis.