Low-coordination single Ni atoms on graphitic C3N4 for nitrite electroreduction to ammonia

Abstract

Electrocatalytically converting NO₂⁻ to NH₃ (NO₂RR) offers an attractive approach to realize both hazardous NO₂⁻ abatement and sustainable NH₃ production. Single-atom catalysts (SACs) show a great potential for N-cycle electrocatalysis, whereas their application for the NO₂RR remain largely unexplored. In this study, isolated Ni atoms on graphitic C₃N₄ (Ni₁/C₃N₄) are explored as an efficient catalyst towards the NO₂RR. Atomic coordination characterizations reveal the construction of low-coordination Ni₁–N₂ moieties on Ni₁/C₃N₄. Theoretical calculations unveil that Ni₁–N₂ moieties serve as active centers to promote the activation of NO₂⁻ and minimize the energy barrier of the *NO → *NOH rate-determining step, whilst inhibiting the competitive hydrogen evolution. As a result, Ni₁/C₃N₄ exhibits a high NH₃-faradaic efficiency of 96.9% with a corresponding NH₃ yield rate of 483.3 μmol h⁻¹ cm⁻² at −0.7 V. RHE, along with an excellent electrocatalytic stability.