TiO-MoC Heterostructure for Enhanced Electrocatalytic Nitrogen Reduction to Ammonia.

The development of catalysts with high activity and selectivity for the electrochemical nitrogen reduction reaction (NRR) remains crucial. Molybdenum carbide (MoC) shows promise as an electrocatalyst for NRR but faces challenges due to the difficulty of N adsorption and activation as well as the competitive hydrogen evolution reaction. In this study, we propose a strategy of combining TiO with MoC to form heterostructure catalysts. Our first-principles theoretical calculations indicate that the TiO-MoC heterostructure exhibits enhanced N adsorption and activation, attributed to the increased interaction between the π orbital of Mo and the π orbital of N, facilitated by the directional modulation of Mo's d-orbitals by TiO. A more positive integrated crystal orbital Hamilton population and an elongated N≡N bond length prove this. Additionally, the higher Gibbs free energy for N compared to that for H demonstrates a preference for N adsorption. We further elucidate the catalytic mechanism for converting N to NH on the TiO-MoC surface, identifying the associative distal pathway as the dominant route over the associative alternating pathway. This work highlights unique advantages of the TiO-MoC heterostructure for the NRR and provides theoretical guidance for designing efficient NRR electrocatalysts.