Terbium- and samarium-doped Li2ZrO3 perovskite materials as efficient and stable electrocatalysts for alkaline hydrogen evolution reactions

The preparation of highly active, rare earth, non-platinum-based catalysts for hydrogen evolution reactions (HER) in alkaline solutions would be useful in realizing green hydrogen production technology. Perovskite oxides are generally regarded as low-active HER catalysts, owing to their unsuitable hydrogen adsorption and water dissociation. In this article, we report on the synthesis of Li₂ZrO₃ perovskites substituted with samarium and terbium cations at A-sites for the HER. LSmZrO₃ (LSmZO) and LTbZrO₃ (LTbZO) perovskite oxides are more affordable materials, starting materials in abundance, environmentally friendly due to reduced usage of precious metal and moreover have potential for several sustainable synthesis methods compared to commercial Pt/C. The surface and elemental composition of the prepared materials have been confirmed by X-ray photoelectron spectroscopy (XPS). The morphology and composition analyses of the LSmZO and LTbZO catalysts showed spherical and regular particles, respectively. The electrochemical measurements were used to study the catalytic performance of the prepared catalyst for hydrogen evolution reactions in an alkaline solution. LTbZO generated 2.52 mmol/g/h hydrogen, whereas LSmZO produced 3.34 mmol/g/h hydrogen using chronoamperometry. This was supported by the fact that the HER electrocatalysts exhibited a Tafel slope of less than 120 mV/dec in a 1.0 M alkaline solution. A current density of 10 mA/cm² is achieved at a potential of less than 505 mV. The hydrogen production rate of LTbZO was only 58.55%, whereas LSmZO had a higher Faradaic efficiency of 97.65%. The EIS results demonstrated that HER was highly beneficial to both electrocatalysts due to the relatively small charge transfer resistance and higher capacitance values.