A Density Functional Theory Study of Electrochemical Nitrogen Reduction to Ammonia on the (100) Surface of Transition-Metal Oxynitrides

The electrochemical nitrogen (N2) reduction reaction (ENRR) to produce ammonia (NH3) under ambient conditions is attractive compared to the energy-and carbon-intensive industrialized Haber-Bosch process. However, efficient catalysts are needed to break an NN bond in an N2 molecule to convert it to NH3. Transition-metal oxynitrides (TMNOs) have shown promising ENRR activities at low potentials. Here, density functional theory (DFT) calculations are performed to study the ENRR activity of TMNO(100) surfaces for TM = Co, Cr, Cu, Fe, Hf, Mn, Nb, Ni, Sc, Ta, Ti, V, Y, Zn, and Zr. Our DFT calculations and microkinetic modeling results show that the ENRR proceeds at a low applied potential on the (100) surfaces of MnNO, CrNO, FeNO, CuNO, HfNO, and VNO. Furthermore, our calculations reveal a volcano-like relation between the limiting potential and binding energy of ENRR intermediates identifying nitrogen binding energy and N2H binding energy as descriptors for ENRR activity on TMNO(100) surfaces.