Pulsed laser interference patterning of transition-metal carbides for stable alkaline water electrolysis kinetics

Abstract

We investigated the role of metal atomization and solvent decomposition into reductive species and carbon clusters in the phase formation of transition-metal carbides (TMCs; namely, Co3C, Fe3C, TiC, and MoC) by pulsed laser ablation of Co, Fe, Ti, and Mo metals in acetone. The interaction between carbon s–p-orbitals and metal d-orbitals causes a redistribution of valence structure through charge transfer, leading to the formation of surface defects as observed by X-ray photoelectron spectroscopy. These defects influence the evolved TMCs, making them effective for hydrogen and oxygen evolution reactions (HER and OER) in an alkaline medium. Co3C with more oxygen affinity promoted CoO(OH) intermediates, and the electrochemical surface oxidation to Co3O4 was captured via in situ/operando electrochemical Raman probes, increasing the number of active sites for OER activity. MoC with more d-vacancies exhibits strong hydrogen binding, promoting HER kinetics, whereas Fe3C and TiC with more defect states to trap charge carriers may hinder both OER and HER activities. The results show that the assembled membrane-less electrolyzer with Co3C∥Co3C and MoC∥MoC electrodes requires ~2.01 and 1.99 V, respectively, to deliver a 10 mA cm−2 with excellent electrochemical and structural stability. In addition, the ascertained pulsed laser synthesis mechanism and unit-cell packing relations will open up sustainable pathways for obtaining highly stable electrocatalysts for electrolyzers. © 2024 The Authors. Carbon Energy published by Wenzhou University and John Wiley & Sons Australia, Ltd.