Bifunctional Electrocatalysts for Alkaline Water Electrolysis Derived from Metal-Containing Ionic Liquids

Abstract

Carbon-based electrocatalysts decorated with Pt and Ni nanoparticles were introduced herein to increase the efficiency of the water splitting process and thus reduce the price of the produced green hydrogen. The materials were prepared by innovative direct carbonization of ionic liquids containing the corresponding metal, thereby eliminating the need for additional solutions and templates. The structural integrity of the materials was validated through X-ray diffraction analysis and Fourier-transform infrared spectroscopy. The electrochemical performance of these materials in catalyzing hydrogen (HER) and oxygen (OER) evolution reactions was evaluated using voltammetry and electrochemical impedance spectroscopy, uncovering distinct behaviors and highlighting the role of ionic liquid in tailoring materials’ properties and performance. Specifically, the presence of Ni was observed to enhance the catalytic performance towards the HERs due to the interaction of Ni nanoparticles and a higher amount of sp²-hybridized carbon present. In contrast, incorporating Pt into the carbon matrix was found to augment the catalytic activity for OERs with a Tafel slope of 129 mV dec⁻¹ and a current density of 10 mA cm⁻² reached at a potential of 1.67 V. Moreover, chronoamperometric measurements evidenced materials’ steady performance under both HER and OER conditions. These findings of good activity and stability showed that the introduced approach of synthesis of carbon electrocatalysts decorated with heteroatoms by direct carbonization of ionic liquids holds great promise for the synthesis of efficient and affordable electrocatalysts for green hydrogen production.