Innovative mechanical exfoliation process of screen-printed CNT-integrated Fe₂NiSi-NiSi electrocatalyst for efficient water-splitting

Synthesis of cost-effective, high-performance electrocatalysts for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) remains challenging. Herein, we report a novel approach to the synthesis of efficient electrocatalyst using silicon (Si), nickel (Ni), and carbon nanotube (CNT) on a Kovar (nickel-cobalt ferrous alloy) substrate via screen-printing and vacuum annealing. Initially, Si nanoparticles were screen-printed on a Kovar substrate. Subsequent vacuum annealing induces a solid-state diffusion reaction between Si and substrate, resulting in the formation of an Fe₂NiSi Heusler phase that enriched catalytically active Fe and Ni metals. To further enhance catalytic activity, the unreacted Si was eliminated by introducing Ni nanoparticles, converting Si to an electrically conductive NiSi phase. Furthermore, these phases agglomerate at high temperatures, resulting in poor catalytic activities. The incorporation of CNT suppressed agglomeration, improved conductivity, and enhanced surface area. Additionally, the mechanical exfoliation strategy which is the key innovation of this study offers high exposure to active sites by protruding buried catalytic sites. The resulting CNT-Integrated Fe₂NiSi-NiSi electrocatalyst demonstrated low overpotentials of 57 mV for HER and 200 mV for OER at 10 mA cm⁻². As a bifunctional catalyst, it delivered an electrolyzer cell voltage of 1.491 V, comparable to conventional electrode systems.