Key Takeaways & Executive Findings
- •• • Ru-Ni(OH)2/NF achieves a record-low HER overpotential of 9.6 mV at 10 mA cm−2 in alkaline media, outperforming Pt/C and most reported catalysts, directly addressing the kinetic bottleneck of water dissociation. • • The catalyst exhibits an exceptionally low potential of 0.015 V vs. RHE for hydrazine oxidation at 100 mA cm−2, enabling energy-efficient hydrogen production coupled with hydrazine degradation. • • The overall hydrazine splitting (OHzS) system requires only 0.09 V to deliver 50 mA cm−2, which is 1.637 V lower than overall water splitting, representing a significant reduction in energy input for hydrogen generation. • • Chronoamperometry shows negligible current decay at 30 mA cm−2 over 30 hours, with SEM and XPS confirming structural stability, indicating robust long-term operation for industrial applications.
Abstract
Sluggish water dissociation kinetics in the alkaline hydrogen evolution reaction (HER) hamper its practical production. Here, a heterojunction electrocatalyst featuring Ru-Ni(OH)2 interfaces on nickel foam (NF) with self-engineered built-in electric fields (BIEF) was synthesized via a simple in situ galvanic replacement reaction. The hierarchical Ru-Ni(OH)2/NF exhibits a record overpotential of 9.6 mV at 10 mA cm−2 for alkaline HER, surpassing most reported catalysts and commercial Pt/C. It also shows exceptional activity for hydrazine oxidation reaction (HzOR) at 100 mA cm−2 with a remarkably low potential of ca. 0.015 V vs. RHE. The assembled overall hydrazine splitting (OHzS) system integrating HER and HzOR requires a cell voltage of about 0.09 V to reach 50 mA cm−2, which is 1.637 V lower than the corresponding overall water splitting (OWS) device. Systematic analysis and calculation reveal that the BIEF induces redistribution of interfacial electrons for Ru, facilitating H2O dissociation and intermediate conversion, delivering ultra-high electrocatalytic performance. This work provides an avenue for design and preparation of electric field-mediated catalysts towards sustainable energy conversion.
1. Introduction
Alkaline water electrolysis is a cornerstone for sustainable hydrogen production due to its industrial scalability, but its cathodic hydrogen evolution reaction (HER) suffers from sluggish kinetics stemming from the multi-step water dissociation (Volmer step) and hydrogen adsorption/desorption (Heyrovsky/Tafel steps). Pt-based catalysts, though benchmarked with optimal hydrogen adsorption free energy, exhibit insufficient hydroxyl adsorption in alkaline media, leading to reduced activity, and their scarcity and cost hinder large-scale deployment.
To overcome these limitations, heterointerface engineering has emerged as a promising strategy to decouple the interdependent Volmer and Heyrovsky/Tafel steps. Ruthenium (Ru) possesses favorable hydrogen binding energy and hydroxyl affinity, yet its water dissociation efficiency remains low due to misaligned electron density. This work introduces a built-in electric field (BIEF) at Ru-Ni(OH)2 interfaces, fabricated via a simple galvanic replacement reaction, to redistribute interfacial electrons and enhance water dissociation kinetics, achieving record-low overpotential and exceptional performance in both HER and hydrazine oxidation.
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Jianli Yu, Yongli Shen, Pei Zhu, Lina Li, Changhua An (2026). Facile Construction of Self-Supported Ru-Ni(OH)2 with Built-In Interfacial Electric Field for Accelerating Hydrogen Evolution. SCIENCE CHINA Materials. https://doi.org/10.1007/s40843-025-3564-9
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Frequently Asked Questions
What is the specific overpotential at 10 mA cm−2 and how does it compare to Pt/C?
The Ru-Ni(OH)2/NF catalyst exhibits an overpotential of 9.6 mV at 10 mA cm−2 in alkaline HER, which is lower than commercial Pt/C and most reported catalysts, indicating superior intrinsic activity.
How does the built-in electric field enhance the catalytic performance?
The BIEF induces electron redistribution at the Ru-Ni(OH)2 interface, optimizing the electronic configuration of Ru active sites. This facilitates water dissociation and intermediate conversion, as confirmed by systematic analysis and theoretical calculations.
What is the stability of the catalyst under prolonged operation?
Chronoamperometry tests show negligible current decay at 30 mA cm−2 over 30 hours, and post-reaction SEM and XPS analyses confirm that the microstructure and chemical states remain unchanged, demonstrating excellent stability.
What is the energy saving potential of the overall hydrazine splitting system compared to water splitting?
The OHzS system requires a cell voltage of only 0.09 V to reach 50 mA cm−2, which is 1.637 V lower than the corresponding OWS device, representing a significant reduction in energy consumption for hydrogen production.
How is the catalyst synthesized and is the method scalable?
The catalyst is synthesized via a simple in situ galvanic replacement reaction on nickel foam, which is a facile and potentially scalable method for producing self-supported electrodes without complex procedures.
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