Unveiling the Synergy between Surface Terminations and Boron Configuration in Boron-Based Ti3C2 MXenes Electrocatalysts for Nitrogen Reduction Reaction

The performance of B-containing Ti3C2 MXenes as catalysts for the nitrogen reduction reaction (NRR) is scrutinized using density functional theory methods on realistic models and accounting for working conditions. The present models include substituted and adsorbed boron along with various mixed surface terminations, primarily comprising -O and -OH groups, while considering the competitive hydrogen evolution reaction (HER) as well. The results highlight that substituted and low-coordinate adsorbed boron atoms exhibit a very high N-2 adsorption capability. For NRR, adsorbed B atoms yield lower limiting potentials, especially for surfaces with mixed -O/-OH surface groups, where the latter participate in the reaction lowering the hydrogenation reaction energy costs. The NRR does also benefit of having B adsorbed on the surface which on moderate -OH terminated model displays the lowest limiting potential of -0.83 V, competitive to reference Ru and to HER. The insights derived from this comprehensive study provide guidance in formulating effective MXene-based electrocatalysts for NRR.