One-step synthesized NbO-decorated spinel-type (Ni,V,Mn)O nanoflowers for boosting electrocatalytic reduction of nitrogen into ammonia

Two renewable methods for reducing greenhouse gas emissions associated with ammonia (NH 3 ) production are the renewable H 2 -combined Haber-Bosch process and the electrochemical nitrogen reduction reaction (eNRR). However, progress in eNRR has fallen short of expectations. Here, we demonstrated a well-controlled electrochemically viable and clean NH 3 production with spinel-type (V,Ni,Mn) 3 O 4− x /Nb 2 O 5− y nanoflowers, successfully synthesized via a facile one-pot hydrothermal method on nickel foam, aimed at boosting the eNRR performance, after surveying many Ni-V-Mn-Nb quaternary, ternary, and binary oxide systems for their electrochemical and structural properties. The best NH 3 yield from a quaternary system exhibited the most promising results, achieving 3.19 mg h −1 cm −2 (1.28 mg h −1 mg cat. −1 ) at a potential of −0.5 V vs. RHE, with a remarkable faradaic efficiency (FE) of 22.7%, which is superb among the current state of the art methods. Besides, the electrocatalyst performance, evaluated in terms of energy conversion, showed a cell energy efficiency of 37.66%. An N&z.tbd;N bond-weakening micro-mechanism of electron transport for the nonstoichiometric Ni-V-Mn-Nb oxide system is proposed to elucidate this exceptional activity. Furthermore, we suggest a reaction micro-mechanism encompassing electron transport and N 2 trapping, contributing to the observed excellent activity in NH 3 production. Two renewable methods for reducing greenhouse gas emissions associated with ammonia (NH 3 ) production are the renewable H 2 -combined Haber-Bosch process and the electrochemical nitrogen reduction reaction (eNRR).