Engineering highly selective NO3RR electrocatalysts: Integrating 2D materials with Nb-doped TiN for sustainable ammonia synthesis

The electrocatalytic nitrate reduction reaction (NO   3RR) offers a promising approach for sustainable ammonia synthesis and environmental remediation. However, developing efficient and selective catalysts for NO   3RR remains a significant challenge, particularly in suppressing competing reactions and byproduct formation. This study investigates the potential of two-dimensional (2D) material/Nb-doped TiN heterojunctions as electrocatalysts for NO   3RR using density functional theory calculations. Among the explored systems, BN/Nb@TiN, BP/Nb@TiN, Gra/Nb@TiN, and g-C   3N   4/Nb@TiN exhibited superior catalytic performance, with potential-determining step free energy changes as low as 0.52 eV. Importantly, Nb doping enhances the selectivity of 2D/TiN heterostructures for NO   3RR by favoring the *NO → *NOH pathway over *NO dimerization to *N   2O   2, thereby improving ammonia production efficiency. These catalysts effectively suppress the hydrogen evolution reaction (HER) while simultaneously inhibiting the formation of byproducts such as NO and NO   2. Mechanistic analysis revealed that the synergistic effect between 2D materials and Nb-doped TiN surfaces significantly improves nitrate activation and N-O bond weakening. This work provides valuable insights into the synergistic integration of heterogeneous diatomic catalysts within heterojunction structures, offering a promising direction for designing high-performance NO   3RR electrocatalysts for selective and efficient sustainable ammonia production and nitrate pollution control.