Metal-substituted zirconium diboride (Zr= Ni, Co, and Fe) as low-cost and high-performance bifunctional electrocatalyst for water splitting

Abstract

Recent years have witnessed an unprecedented surge in research on earth-abundant and efficient electrocatalysts for the water splitting process. Among those, the development of boron-based advanced catalysts is subject to designing the active and durable compounds, working as bifunctional materials under alkaline medium. In this study, a series of ZrB2-based catalysts with a general formula of Zr(1-x)TMxB2 (x = 0.05, 0.1, and 0.2) (TM = Fe, Co, and Ni) were prepared through a straightforward route and employed as bifunctional electrocatalysts in hydrogen and oxygen evolution reactions (HER and OER). The electrochemical measurements confirmed that the incorporation of Ni into the crystal structure of ZrB2 in the Zr0.8Ni0.2B2 sample led to an onset potential of 1.58 V in OER at a current density of 10 mA cm(-2), indicating a remarkable performance with a very low overpotential of 350 mV. Besides, Zr0.8Ni0.2B2 displayed an infinitesimal value of 56.6 mV dec(-1) regarding the Tafel slope, which was lesser as compared to the commercial RuO2 (66.2 mV dec(-1)). For the case of HER, Zr0.8Co0.2B2 showed the best performance compared to other samples with an overpotential of 420 mV and a Tafel slope of 101.6 mV dec(-1), following the Volmer mechanism. Both catalysts were examined for their long-term stability, manifesting excellent catalytic durability even after 12 h. Surprisingly, Zr0.8Co0.2B2 exhibited a drop from 420 to 380 mV in the overpotential value after 1000 CV sweeps, providing a promising performance in terms of HER. As-prepared metal-substituted ZrB2 electrocatalysts have great potential to be implemented in various green energy system applications. (C) 2021 Elsevier Ltd. All rights reserved.