Carbon-Encapsulated Ruthenium Catalyst Enables Low-Energy Hydrogen Production with Simultaneous Wastewater Treatment

A research team from Gyeongsang National University has developed a pulsed-laser-fabricated ruthenium@carbon catalyst that significantly enhances the efficiency of hydrazine-assisted hydrogen production. Published in eScience in September 2025, the study demonstrates how the optimized Ru@C-200 catalyst achieves ultralow overpotentials for both hydrogen evolution and hydrazine oxidation. The researchers further integrate the catalyst into a zinc–hydrazine battery and a hybrid hydrazine-splitting electrolyzer, enabling continuous self-powered hydrogen generation while simultaneously degrading hydrazine.

Hydrogen is expected to play a central role in future carbon-neutral energy systems, but conventional water electrolysis is hindered by the slow and energy-intensive oxygen evolution reaction. Replacing this step with hydrazine oxidation significantly reduces the voltage needed for hydrogen production, while converting hydrazine—an industrial pollutant—into harmless nitrogen. The Ru@C-based catalytic system provides a compelling route for hydrogen production at voltages dramatically lower than those required for traditional electrolysis, offering substantial energy savings.

The researchers synthesized the ruthenium@carbon material using a pulsed-laser ablation-in-liquid strategy that produced uniform Ru nanospheres encapsulated within graphitic carbon shells. Among all samples, Ru@C-200 displayed the most favorable balance of conductivity, structural stability, and electronically coupled metal–carbon interfaces. This optimized design enabled a low overpotential of 48 mV for hydrogen evolution and only 8 mV for hydrazine oxidation at 10 mA cm⁻², far outperforming conventional electrocatalysts.

When tested in a hydrazine-splitting electrolyzer, a Ru@C-200‖Ru@C-200 pair required only 0.11 V to achieve 10 mA cm⁻² and maintained stability for over 100 hours. The team further demonstrated a rechargeable Zn–hydrazine battery capable of powering hydrogen production independently. The battery achieved 90% energy efficiency and remained stable across 600 charge–discharge cycles. These results underscore how engineered Ru–C interfaces simultaneously improve activity, selectivity, and durability for both anodic and cathodic reactions.

According to the research team, the Ru@C-200 catalyst stands out for its rare combination of low energy consumption, long-term durability, and bifunctional catalytic capability. The expert emphasized that strong electronic coupling between the ruthenium core and carbon shell plays a pivotal role in accelerating charge transfer and efficiently activating hydrazine and hydrogen-related intermediates. They noted that this interface-engineered design demonstrates how a single multifunctional catalyst can address the dual needs of lowering hydrogen production costs and eliminating hazardous hydrazine pollutants.

The ability to completely oxidize hydrazine while generating hydrogen positions this technology as a practical solution for industries that manage hydrazine-rich wastewater. The successful coupling with a rechargeable Zn–hydrazine battery illustrates a self-powered model in which hydrogen production, waste treatment, and energy storage occur simultaneously. This approach may accelerate the adoption of safer, more efficient hydrogen infrastructures and inspire new hydrazine-assisted technologies tailored for clean energy conversion and environmental remediation. The findings highlight a promising strategy to combine green energy generation with pollutant removal using a single multifunctional electrocatalyst.