Unveiling the Activity Origin of a Copper‐based Electrocatalyst for Selective Nitrate Reduction to Ammonia

Abstract

Unveiling the active phase of catalytic materials under reaction conditions is important for the construction of efficient electrocatalysts for selective nitrate reduction to ammonia. The origin of the prominent activity enhancement for CuO (Faradaic efficiency: 95.8 %, Selectivity: 81.2 %) toward selective nitrate electroreduction to ammonia was probed. 15N isotope labeling experiments showed that ammonia originated from nitrate reduction. 1H NMR spectroscopy and colorimetric methods were performed to quantify ammonia. In situ Raman and ex situ experiments revealed that CuO was electrochemically converted into Cu/Cu2O, which serves as an active phase. The combined results of online differential electrochemical mass spectrometry (DEMS) and DFT calculations demonstrated that the electron transfer from Cu2O to Cu at the interface could facilitate the formation of *NOH intermediate and suppress the hydrogen evolution reaction, leading to high selectivity and Faradaic efficiency.

Rational design on photo(electro)catalysts for artificial nitrogen looping

“…The direct reduction of nitrate to ammonia could provide a more promising strategy for ammonia industry in the future due to higher solubility and activity of nitrate in aqueous solution than that of nitrogen gas. 165 etc. ), and so on.…”

“…In this field, the main catalysts include metals (eg, Al, 159 Cu, 160 Cu‐Ni, 161 etc. ), metal compounds (Co 3 O 4 , 162,163 ), metal composites (eg, Ni/TiO 2 , 164 Cu/Cu 2 O, 165 etc. ), and so on.…”

Alloying effect-induced electron polarization drives nitrate reduction to ammonia

“…Therefore, the (111) surface of Cu2O, as the most stable surface, was chosen to be reconstructed as the slab model, featuring a [3×3] supercell and three Cu2O layers. 13 The slab model of PdCu was constructed by loading a triatomic cluster of Pd on the Cu2O…”

“…[10][11][12] As an alternative, electrocatalytic N2 reduction at ambient conditions with proton derived from decomposition of H2O has recently attracted research interest. 13 However, a low yield rate and a low achievable selectivity at high current densities has plagued its future. 14 Among all the nitrogencontaining alternatives, nitrate (NO3 -) is undoubtedly the most promising.…”

“…[15][16] The disintegration of NO3into the deoxygenated species only requires an energy of 204 kJ/mol, much lower than the cleavage energy of N≡N bond (941 kJ/mol). [13][14] Meanwhile, higher reaction energy barrier for N2 reduction occurring at solid-gas-liquid interfaces is demanded compared to that of nitrate reduction reaction (NITRR) at solid-liquid interfaces. [15][16] In view of energy consumption, exploring the electrocatalytic NITRR makes perfect sense for low temperature NH3 synthesis.…”