Single-Crystalline NiO Octahedron with (111) facet as a Bifunctional Electrocatalyst for Overall Water Splitting

Abstract

The production of hydrogen energy through electrocatalysis has garnered significant attention due to its minimal environmental pollution. To achieve cost parity for electrolysis technology, there is a pressing need for a non-precious, stable, and earth-abundant transition metal-based bifunctional catalyst that can efficiently facilitate water splitting. Developing cost-effective and efficient electrocatalysts for overall water splitting remains a significant challenge. Faceted crystals with highly reactive planes have garnered considerable attention for this purpose. In this study, we present the synthesis of octahedron-shaped NiO crystals with 100% dominantly exposed {111} reactive facets. The octahedron-shaped NiO is demonstrated as a potential bifunctional electrocatalyst for both HER and OER in an alkaline medium. For hydrogen evolution, 371.0 mV overpotential is required to achieve a current density of 10 mA/cm² whereas for oxygen evolution, 389.6 mV overpotential is sufficient to produce a current density of 10 mA/cm². Notably, the {111} reactive facets of NiO crystals exhibit a cell potential of 1.99 V for overall water splitting and show excellent stability with a negligible current density change in 12 h.