# Tuning the Hydrogen Evolution Activity of Co2NiO4 via Precursor-Controlled Synthesis

## TL;DR

Researchers developed a new method to improve the efficiency of hydrogen production using a common material by controlling its structure during synthesis.

## Contribution

A precursor-controlled synthesis method is introduced to enhance the hydrogen evolution activity of Co2NiO4 through morphology and surface-state regulation.

## Key findings

- A hydrothermal strategy using hexamethylenetetramine produces ultrathin, interconnected nanosheets of Co2NiO4 with improved HER performance.
- The CNO-HT catalyst shows a low overpotential (86 mV at 10 mA cm−2) and a Tafel slope of 103 mV dec−1, outperforming urea-derived catalysts.
- The catalyst maintains stability for 96 hours at high current densities, with preserved kinetics and interfacial properties.

## Abstract

The realization of efficient and durable earth-abundant electrocatalysts for alkaline hydrogen evolution reaction (HER) is critical for scalable hydrogen production, yet remains limited by insufficient intrinsic activity. Herein, we demonstrate a precursor-controlled hydrothermal strategy that enables precise morphology and surface-state regulation of spinel Co2NiO4 directly grown on nickel foam, allowing a clear correlation between catalyst architecture and HER performance. By replacing urea with hexamethylenetetramine, an ultrathin, highly interconnected two-dimensional nanosheet network (CNO-HT) is obtained, which promotes efficient electron transport, rapid electrolyte penetration, and maximized exposure of catalytically active sites. Structural and spectroscopic analyses confirm the formation of phase-pure cubic Co2NiO4 with enriched mixed-valence Ni and Co species, favoring enhanced redox activity. The CNO-HT catalyst exhibits a low overpotential (86 mV at 10 mA cm−2) and a smaller Tafel slope (103 mV dec−1), significantly outperforming the urea-derived counterpart. Importantly, the catalyst maintains stable HER operation for 96 h at both 10 and 100 mA cm−2, with post-stability electrochemical analyses confirming preserved kinetics and interfacial properties. This work establishes precursor-regulated nanosheet engineering as general and scalable strategy to unlock the intrinsic catalytic potential of spinel metal oxides, offering actionable design principles for next-generation non-noble electrocatalysts for alkaline hydrogen production.