Integrated selective nitrite reduction to ammonia with tetrahydroisoquinoline semi-dehydrogenation over a vacancy-rich Ni bifunctional electrode

Abstract

The development of efficient electrocatalysts for nitrite reduction to ammonia, especially integrated with a value-added anodic reaction, is important. Herein, Ni nanosheet arrays with Ni vacancies (Ni-NSA-V_Ni) were demonstrated to exhibit outstanding electrocatalytic performances toward selective nitrite reduction to ammonia (faradaic efficiency: 88.9%; selectivity: 77.2%) and semi-dehydrogenation of tetrahydroisoquinolines (faradaic efficiency: 95.5%; selectivity: 98.0%). The origin and quantitative analyses of ammonia were performed by ¹⁵N isotope labeling and ¹H NMR experiments. The decrease in electronic cloud density induced by the Ni vacancies was found to improve the NO₂⁻ adsorption and NH₃ desorption, leading to high nitrite-to-ammonia performance. In situ Raman results revealed the formation of Ni^II/Ni^III active species for anodic semi-dehydrogenation of tetrahydroisoquinolines on Ni-NSA-V_Ni. Importantly, a Ni-NSA-V_Ni‖Ni-NSA-V_Ni bifunctional two-electrode electrolyzer was constructed to simultaneously produce ammonia and dihydroisoquinoline with robust stability and high selectivity.