Unraveling the Electrocatalytic Response of Zn-Substituted Nickel Ferrite for Overall Water Splitting

Abstract

Nickel ferrites (NiFe 2 O 4 ) having rich redox chemistry are regarded as proficient electrocatalysts for sustainable and renewable energy applications. However, its entire potential as an electrode material is limited by its weak structural characteristics and inadequate charge transport qualities. This work reports a series of zinc-substituted inverse spinel ferrites (Zn x Ni 1−x Fe 2 O 4 ) synthesized by a simple and environmentally benign hydrothermal method as electrocatalysts for overall water splitting. The surface morphology, structural elements, and electronic properties of resultant materials are significantly changed by Zn inclusion. Among different compositions, the ferrite sample Zn 0.5 Ni 0.5 Fe 2 O 4 showed outstanding water splitting performances, with a current density of 100 mA•cm −2 for OER and HER at the cost of 290 mV and 311 mV overpotentials, respectively. The electrode demonstrated lower Tafel slopes of 56 and 46 mV•dec −1 for HER and OER with a high turnover frequency (TOF) and exchange current density (j 0 ). Significantly, this electrode demanded a cell voltage of 1.48 V in a two-electrode electrolyzer to deliver 10 mA•cm −2 and showed good stability for 24 h. This is attributed to the efficient charge transport properties of the Zn-incorporated NiFe 2 O 4 with high electrical conductivity and charge transfer characteristics. Overall, the findings highlighted the potential of Zn-incorporated NiFe 2 O 4 as a promising electrocatalyst for renewable hydrogen production.