A transparent iron-incorporated nickel hydroxide electrocatalyst for efficient water oxidation

Developing transparent electrocatalyst films for the oxygen evolution reaction (OER) is indispensable for fabricating a tandem photoelectrochemical device for solar hydrogen production. Herein, we developed a facile solution-based method for depositing highly transparent iron-incorporated nickel hydroxide oxygen evolution electrocatalysts on conductive glass substrates (FTO). The analysis of UV-Vis spectra and electrochemical results of the fabricated electrodes indicated that the incorporation of iron into the nickel hydroxide electrocatalysts greatly influences their transmittance and electrocatalytic activity toward the OER. It increases the conductivity and activates the Ni sites at lower overpotential via stabilizing the OER intermediates as supported by electrochemical impedance measurements. At the optimized iron content, the obtained iron-incorporated nickel hydroxide electrode (FeNi-10) has a nanoplatelet-like morphology, and it requires just 290 mV to generate 10 mA cm⁻² in an alkaline aqueous medium (1.0 M NaOH) with excellent stability. In comparison, a pristine nickel hydroxide electrode requires 384 mV under the same conditions. The overpotential obtained is significantly lower than that of the benchmark RuO₂ and IrO₂ oxide OER electrocatalysts deposited on FTO substrates. The transmittance of the FeNi-10 electrode is comparable to that of the FTO glass. Achieving such cost-effective, highly active, and transparent iron-incorporated nickel hydroxide OER electrodes offers an opportunity to fabricate tandem photoelectrochemical devices for low-cost solar fuel production.