Ultra-thin layers of iridium electrodeposited on Ti2AlC support as cost effective catalysts for hydrogen production by water electrolysis

Abstract

The hydrogen evolution reaction (HER) was investigated in 0.5 M H2SO4 at thin iridium layers electrodeposited on Ti2AlC substrate. Five samples, varying in thickness from 4.5 nm to 255 nm, were electrodeposited from the solution containing K3IrCl6 + Na2SO4. Scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) were applied for morphology and chemical composition analysis. Metallic iridium was detected by X-ray photoelectron spectroscopy (XPS). The HER was investigated by polarization and electrochemical impedance spectroscopy (EIS) measurements. Polarization curves were characterized with the low Tafel slopes ~ −18 mV dec−1, while at higher current densities increased up to −56 mV dec−1. The overpotential at j = −0.1 A cm−2 was ~45 mV, while at j = −0.01 A cm−2 varied from 25.1 mV to 36.1 mV. These novel catalysts exhibited excellent activity, especially under industrial conditions of hydrogen production (j = −0.3 A cm−2) - the determined overpotentials were between 66 and 69 mV only.