Ni-NiO Heterojunction: A Binder-Free Catalyst for Enhanced Oxygen Evolution Reaction
Nastaran Farahbakhsh, Majid Shahsanaei, Patrick Hartwich, Shiva Mohajernia, Manuela S. Killian, Seyedsina Hejazi
Abstract
High Resolution Image Download MS PowerPoint Slide In this study, we applied a two-step electrochemical anodization process to produce highly porous nanostructured nickel suboxides. We then annealed these materials in different environments: air, Ar, and Ar/H 2 . Annealing in a reductive environment (Ar/H 2 ) resulted in a Ni-NiO heterojunction with a high defect density, as confirmed by the Mott–Schottky analysis. Our results demonstrate that these defects and active sites significantly enhance the electrocatalytic activity for the oxygen evolution reaction (OER). Utilizing X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FE-SEM), high-resolution transmission electron microscopy (HR-TEM), and electrochemical analysis, we demonstrate that the heterojunction system containing Ni-NiO, formed through annealing in an Ar/H 2 atmosphere, acts as a highly efficient electrocatalyst for the OER. This catalyst achieves an impressively low overpotential of 293 mV at 10 mA cm –2, a Tafel slope of 74 mV dec –1, and exhibits outstanding stability, maintaining performance over 1000 cycles. Notably, our most optimized NiO x electrode outperforms the conventional reference RuO 2 electrode by a factor of 1.72. Our findings demonstrate the potential of binder-free Ni-NiO heterojunctions in developing high-performance electrocatalysts for alkaline electrolysis.