Influence of Cu2O Precursor Surface Orientation on Catalytic Performance and Product Selectivity in Nitrate Reduction Reactions.

Oxide-derived copper (OD-Cu) has attracted considerable attention due to its exceptional electrocatalytic performance toward various reactions, including the reduction of nitrate (NO₃ ^-) to ammonia (NH₃). Furthermore, numerous techniques have been developed to synthesize copper oxides with well-defined surface orientations. However, the relationship between the surface orientation of the precursor and the NO₃ ^- reduction performance of the resulting OD-Cu catalyst remains unclear. In this study, two types of OD-Cu electrodes, prepared by reducing copper oxide (Cu₂O) with exposed (100) and (111) facets grown on Cu substrates, were employed for NO₃ ^- reduction. The OD-Cu catalyst derived from Cu₂O(111) exhibited a lower overpotential for initiating NO₃ ^- reduction and achieved a higher current density compared to the catalyst derived from Cu₂O(100). Conversely, the catalyst prepared from Cu₂O(100) demonstrated superior Faradaic efficiency for NH₃ production. These differences are attributed to variations in the preferential reaction steps of NO₃ ^- reduction on each catalyst.