Influence of Cu 2 O Precursor Surface Orientation on Catalytic Performance and Product Selectivity in Nitrate Reduction Reactions

Abstract Oxide‐derived copper (OD−Cu) has attracted considerable attention due to its exceptional electrocatalytic performance toward various reactions, including the reduction of nitrate (NO 3 − ) to ammonia (NH 3 ). 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 NO 3 − reduction performance of the resulting OD−Cu catalyst remains unclear. In this study, two types of OD−Cu electrodes, prepared by reducing copper oxide (Cu 2 O) with exposed (100) and (111) facets grown on Cu substrates, were employed for NO 3 − reduction. The OD−Cu catalyst derived from Cu 2 O(111) exhibited a lower overpotential for initiating NO 3 − reduction and achieved a higher current density compared to the catalyst derived from Cu 2 O(100). Conversely, the catalyst prepared from Cu 2 O(100) demonstrated superior Faradaic efficiency for NH 3 production. These differences are attributed to variations in the preferential reaction steps of NO 3 − reduction on each catalyst.