Scalable Amorphous NiFe(OH)_x/Fe/ Graphene Bifunctional Electrocatalyst via Solution-Corrosion for Water Splitting

Abstract

The quest for net-zero emissions highlights the significance of hydrogen as a clean energy carrier, necessitating efficient production methods. Electrochemical water splitting emerges as a crucial method for hydrogen generation, with its further advancement hinging on the development of effective bifunctional catalysts that are efficient in both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). In this study, we develop the bifunctional electrocatalyst NiFe(OH)x/Fe/ graphene through a simple solution-corrosion approach. The overpotentials required for OER and HER to achieve a current density of 10 mA cm−2 are 237 and 42 mV, respectively, while the overall water splitting occurs at a low cell voltage of 1.51 V for the same current density. Remarkably, the catalyst displays robust stability exceeding 70 h at 20 mA cm−2 in 1 M KOH. When scaled to 10 × 10 cm2, its performance is comparable to that of a smaller size 0.5 × 0.5 cm2 electrode, indicating the scalability of our method and potential for industrial-scale hydrogen production. Trace incorporation of iron and the facilitation by graphene modify the electronic structures and coordination environment in the amorphous NiFe(OH)x/Fe/graphene composite. This alteration enhances the distribution of active sites and reduces kinetic barriers for both HER and OER, thereby increasing its bifunctional catalytic activity. This study not only introduces a novel catalyst design that incorporates in-situ Fe metal powder within OER-active catalysts to generate HER active sites for enabling bifunctionality, but also offers a pathway to manufacture high performance electrocatalysts for industrial applications.