A novel synthesis of NiCo2Se4 nanomaterials and their use as bifunctional catalyst for water electrolysis

Abstract

Efficient noble-metal-free bifunctional electrocatalysts like NiCoSe are key enablers for the transition to green hydrogen production from water electrolysis. The impact of the synthesis method on the performance of such bimetallic heterogeneous catalyst is well-known, yet insufficiently investigated. Herein, a new solvothermal template synthesis of NiCo2Se4 employing NiCo2O4 and Ph3P=Se precursors in dimethylformamide is reported. Supported by electrochemical impedance spectroscopy analysis and electrochemical surface area correction, the resultant NiCo2Se4 nanorods were shown to possess attractive catalytic activities for overall water electrolysis, reaching near unity Faradaic efficiency. To sustain the benchmarking catalytic current density of 10 mA·cm−2, the catalyst required half-cell potentials of −0.45 V and 1.62 V vs Reversible hydrogen electrode for the hydrogen evolution reaction and oxygen evolution reaction in 1 M KOH, respectively, and a full-cell voltage of 2.2 V. The chemical and structural evolution of the material during the catalysis were examined by inductively coupled plasma mass spectrometry, energy-dispersive x-ray spectroscopy elemental mapping, Raman spectroscopy, x-ray photoelectron spectroscopy and scanning electron microscopy, revealing an obvious Se leaching and formation of oxide/hydroxide species in alkaline electrolyte.