Efficient Nitrate Generation through Electrochemical N2 Oxidation with Nickel Oxyhydroxide Decorated Copper Hydroxide Driven by Solar Cells

Abstract

Electrocatalytic nitrogen oxidation reaction (NOR) into nitrate under ambient conditions, as an alternative to replace traditional industrial method, is a promising artificial N₂ fixation strategy, especially powered by renewable energy. Here, through skillfully balancing competitive relationships between NOR and oxygen evolution reaction (OER), the nickel oxyhydroxide decorated Cu(OH)₂ hybrid electrocatalyst with Cu:Ni molar ratio of 1:1 is developed, which achieves outstanding Faradaic efficiency (FE) of 18.7% and yield rate of 228.24 µmol h^-1 g_cat ^-1 at 2.0 V versus reversible hydrogen electrode (RHE) in the electrolyte of 0.1 m Na₂ SO₄ . Also, the hybrid catalyst maintained over five cycles (10 h each cycle) with negligible decay in performance. The synergetic effect between the components of nickel oxyhydroxide and Cu(OH)₂ is found to remarkably activate N₂ and suppress the activity of competitive OER, which enhances NOR performance eventually. Moreover, the conversion efficiency of solar-to-nitrate (STN) with 0.025% was obtained by coupling with a commercial solar cell. This work provides a novel avenue of rational catalysts design strategies and realizes solar-to-nitrate synthesis.

Keywords: Cu(OH) 2; artificial N 2 fixation; electrochemical N 2 oxidation; nickel oxyhydroxide; solar-to-nitrate.