# Accelerated Electro‐Conversion of a Nickel Coordination Complex for Hybrid Water Electrolysis

## TL;DR

A nickel-based pre-catalyst rapidly transforms into active nanosheets during urea electrolysis, enabling efficient and stable hydrogen production.

## Contribution

A hydrazine-coordinated Ni complex is introduced as a pre-catalyst that electrochemically converts into γ-NiOOH nanosheets for urea oxidation.

## Key findings

- The pre-catalyst achieves a low Tafel slope of 21.6 mV dec⁻¹ and a high turnover frequency of 0.0728 s⁻¹.
- The material demonstrates stable operation for over 40 hours of continuous electrolysis.
- In situ spectroscopy reveals the dynamic evolution of active sites and the reaction mechanism.

## Abstract

Electrocatalytic energy conversion relies on the dynamic transformation of electrode materials into “electrocatalytically active phases” under reaction conditions. Pre‐catalysts, which undergo extensive structural and chemical changes during electrochemical activation, are particularly promising in this regard. In the context of electrocatalysis, coordination complexes with labile ligands offer a unique advantage, as they can rapidly reconstruct under electrochemical conditions. Herein, a hydrazine‐coordinated Ni complex embedded in a conductive carbon nanotube matrix is presented as a pre‐catalyst for urea‐assisted hybrid water electrolysis, that transforms into highly active γ‐NiOOH nanosheets on electrochemical activation, demonstrating exceptional urea electrooxidation performance, with a low Tafel slope of 21.6 mV dec−1, a high turnover frequency (TOF) of 0.0728 s−1, and stable operation over 40 h of continuous electrolysis, reflecting superior catalytic kinetics and excellent durability. In situ synchrotron X‐ray absorption, Raman, and electrochemical impedance spectroscopy reveal the dynamic evolution of active sites, the underlying reaction mechanism, and the fate of the active species after prolonged electrolysis. The integration of this pre‐catalyst into an anion‐exchange membrane electrolyzer highlights its potential for practical application. This work showcases the transformative role of Ni‐based coordination complexes as pre‐catalysts, offering an innovative blueprint for the rational design of high‐performance urea oxidation electrocatalysts.

A nickel coordination complex pre‐catalyst undergoes rapid electrochemical activation to form highly active nanosheets that enable efficient and stable urea electrolysis. Structural evolution and the operating mechanism are revealed through in situ spectroscopy, and practical viability is demonstrated in an electrolyzer. This smart (pre‐)catalyst design strategy, enables cleaner and more efficient hydrogen generation.