TiO2–Mo2C 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 (Mo2C) shows promise as an electrocatalyst for NRR but faces challenges due to the difficulty of N2 adsorption and activation as well as the competitive hydrogen evolution reaction. In this study, we propose a strategy of combining TiO2 with Mo2C to form heterostructure catalysts. Our first-principles theoretical calculations indicate that the TiO2–Mo2C heterostructure exhibits enhanced N2 adsorption and activation, attributed to the increased interaction between the π4d* orbital of Mo and the π2p* orbital of N2, facilitated by the directional modulation of Mo’s d-orbitals by TiO2. A more positive integrated crystal orbital Hamilton population and an elongated N≡N bond length prove this. Additionally, the higher Gibbs free energy for N2 compared to that for H demonstrates a preference for N2 adsorption. We further elucidate the catalytic mechanism for converting N2 to NH3 on the TiO2–Mo2C surface, identifying the associative distal pathway as the dominant route over the associative alternating pathway. This work highlights unique advantages of the TiO2–Mo2C heterostructure for the NRR and provides theoretical guidance for designing efficient NRR electrocatalysts.