Theoretical investigation of nitrate adsorption and electronic interactions on CoP surfaces

• Investigation of nitrate adsorption on various low-index CoP surfaces using DFT. • Identified the most stable and active CoP surfaces for NO 3 - RR. • CoP (001), (010), and (101) surfaces exhibit efficient electron interaction with NO 3 - . • Key hybridization between Co 3 d and P 2 p orbitals, stabilizing‌ NO 3 - adsorption. This study investigates the adsorption behavior and electronic interactions of nitrate (NO 3 - ) on the low-index surfaces of cobalt phosphide (CoP) using density functional theory (DFT). The goal is to identify the active and stable surfaces of CoP for use as catalysts in hydrogenation reactions. The results show that the catalytic activity of CoP is highly surface-dependent. Among the low-index surfaces, the (001), (010), and (101) surfaces exhibit the most favorable adsorption energies for NO 3 - . The bond formation mechanisms and electronic interactions between CoP and the adsorbed NO 3 - were further explored through charge density difference, plane-averaged charge density difference, and density of states (DOS) analysis. To enhance the practical relevance of the theoretical predictions, implicit solvation effects were evaluated using a continuum water model, and a representative reaction barrier for the initial NO 3 - hydrogenation step on the CoP (010) surface was estimated to be 0.78 eV. Comparative analysis with NiP and FeP surfaces further confirmed the superior NO 3 - adsorption capacity of CoP. This work provides valuable insights for further research on electrocatalytic nitrate reduction and the development of efficient CoP-based catalysts for energy conversion processes.