Binder-Free HfNi-Doped WO3 Bifunctional Electrocatalysts for Efficient Seawater Electrolysis

Abstract

Electrochemical water splitting is a promising renewable energy generation method. Recently, the development of nonprecious water-splitting electrocatalysts has gained attention. However, it is challenging to discover nonprecious electrocatalysts that work well in hydrogen and oxygen evolution reactions. The hydrothermal hafnium nickel tungsten oxide production on nickel foam (HfNi-WO₃@NF) nanomaterials resulted in an efficient electrocatalyst. The synthesized electrocatalyst’s performance was excellent for the oxygen evolution reactions (OER) and the hydrogen evolution reactions (HER). The HER and OER require 106 and 246 mV overpotentials to 10 mA/cm² and 20 mA/cm² of current density. Likewise, in alkaline conditions (1 M KOH), the HER and OER need a decreased Tafel slope, 45 mV/dec for HER and 38 mV/dec for OER, to remain stable over an extended duration. A water-splitting electrolyzer using HfNi-WO₃@NF bifunctional nonprecious electrocatalyst generates a current density of 10 mA/cm² at 1.52 V and 1000 mA/cm² at 1.87 V. The same electrocatalysts have been used for seawater, requiring only 1.68 V with high durability under high current conditions for gravity-precipitated seawater samples. Nonprecious electrocatalysts are promising for hydrogen generation in abundant seawater electrolysis.