Synergism of Interfaces and Defects: Cu/Oxygen Vacancy-Rich Cu-Mn₃O₄ Heterostructured Ultrathin Nanosheet Arrays for Selective Nitrate Electroreduction to Ammonia

Abstract

Achieving high efficiency in nitrate (NO 3 − ) to ammonia (NH 3 ) electrocatalysis requires the exploration of advanced electrocatalysts with a welldesigned composition and architecture. In this work, a facile one-step hydrothermal approach was developed for the construction of novel Cu/oxygen vacancy-rich Cu-Mn 3 O 4 heterostructured ultrathin nanosheet arrays on Cu foam (Cu/Cu-Mn 3 O 4 NSAs/CF). Two-dimensional ultrathin nanosheet arrays could increase the exposure of catalytically active centers, and the heterogeneous nanointerface and oxygen vacancies synergistically improve the nitrate-to-ammonia activity over the active centers. Due to the desirable compositional and structural advantages, the Cu/Cu-Mn 3 O 4 NSAs/CF demonstrated excellent performance for the electrocatalytic nitrate reduction to ammonia with high ammonia selectivity (87.6%) and Faradic efficiency (92.4%).

Interfacial Engineering Enhances the Electroactivity of Frame‐Like Concave RhCu Bimetallic Nanocubes for Nitrate Reduction

“…− -RR at PA-RhCu cNCs at 0.05 V applied potential are much higher than most reported values at various electrocatalysts (Table S1, Supporting Information), [29,[44][45][46][47][48][49][50][51][52] proving the high NO 3 − -RR activity of PA-RhCu cNCs. Obviously, the high apparent NO 3 − -RR activity of PA-RhCu cNCs directly benefits from the high ECASA derived from the unusual frame-like concave nanocube structure with hollow, pore-like and dendritic features.…”

“…The fact indicates high NH 3 yield of NO 3 − ‐RR at PA‐RhCu cNCs originates from the KNO 3 electroreduction rather than N‐containing pollution species in the experimental environment. [ 55,56 ] Furthermore, it is observed that the NH 3 yield and faradaic efficiency of NH 3 for NO 3 − ‐RR at PA‐RhCu cNCs at 0.05 V applied potential are much higher than most reported values at various electrocatalysts (Table S1, Supporting Information), [ 29,44–52 ] proving the high NO 3 − ‐RR activity of PA‐RhCu cNCs. Obviously, the high apparent NO 3 − ‐RR activity of PA‐RhCu cNCs directly benefits from the high ECASA derived from the unusual frame‐like concave nanocube structure with hollow, pore‐like and dendritic features.…”

“…This fact indicates that the H source for NO 3 − ‐RR at PA‐RhCu cNCs and Rh NPs originates from the underpotentially deposited H (H upd ) at Rh surface rather than HER at Rh surface. [ 28 ] As a result, the onset reduction potential of NO 3 − ‐RR at Rh surface is much lower than that at various nonprecious metal based electrocatalysts (Table S1, Supporting Information), [ 29,44–52 ] showing an energy‐saving electrocatalytic process for NO 3 − ‐RR.…”

“…− -RR at PA-RhCu cNCs and Rh NPs originates from the underpotentially deposited H (H upd ) at Rh surface rather than HER at Rh surface. [28] As a result, the onset reduction potential of NO 3 − -RR at Rh surface is much lower than that at various nonprecious metal based electrocatalysts (Table S1, Supporting Information), [29,[44][45][46][47][48][49][50][51][52] showing an energy-saving electrocatalytic process for NO 3 − -RR. The influence of applied potential on the activity and selectivity of NO 3 − -RR at PA-RhCu cNCs and Rh NPs were investigated by the chronoamperometry measurements at different applied potentials.…”

Efficient electrocatalytic reduction of nitrate to nitrogen gas by a cubic Cu2O film with predominant (111) orientation

“…Moreover, Cu-based materials have attracted increasing attention for reduction of nitrate due to additional advantages, for instance, low cost compared with other noble metals. For example, Cu/Cu-Mn 3 O 4 /Cu foam, 20 defective CuO, 21 CuO nanowire arrays, 22 Cu nanosheets, 23 and three-dimensional Cu nanobelts were applied as the cathodes for nitrate reduction. 13 However, high selectivity and faradaic efficiency for ammonia were generally achieved on the above materials, as well as extra addition of Cl − usually being required to obtain high selectivity towards N 2 .…”