S-Doped Ni(OH)2 nano-electrocatalyst confined in semiconductor zeolite with enhanced oxygen evolution activity

Abstract

Low-cost Ni(OH)₂-based nanomaterials with various structures and morphologies are promising catalysts for efficient oxygen evolution reactions (OERs). However, homogenous Ni(OH)₂ nanomaterials with abundant active sites suffer from low conductivity and easy aggregation, resulting in low catalytic activity and stability. Here, we report a new synthetic method capable of generating abundant and confined S-doped β-Ni(OH)₂ nanoparticles (NPs) (3–5 nm) within a 3D semiconductor substrate, metal-chalcogenide semiconductor zeolite (CSZ). This method operates via sequential fluoride-assisted cationic stripping and in situ Ni(OH)₂ generation and is demonstrated here as an effective method to synthesize Ni²⁺-containing CSZ that are known to defy direct synthesis. The resulting composite (denoted Ni(OH)₂ NPs@CSZ) exhibited excellent OER performance with a very low overpotential of only 212 mV at a current density of 10 mA cm⁻² in O₂-saturated 1 M KOH solution, and low Tafel slope of 64.2 mV dec⁻¹, which is superior to that of benchmark IrO₂. DFT calculations indicate that the interaction between the embedded Ni(OH)₂ NPs and the dopant, S²⁻, from the host CSZ played a crucial role in improving OER performance. This work provides a new path for developing high-performance Ni(OH)₂-based OER catalysts and may also serve as a general approach for loading large amounts of other catalytically active NPs into semiconducting open frameworks to further optimize electrocatalytic performance.