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

A research team from Gyeongsang National University has developed a pulsed-laser-fabricated ruthenium@carbon catalyst that dramatically enhances the efficiency of hydrazine-assisted hydrogen production while simultaneously degrading this industrial pollutant. Published in eScience with DOI 10.1016/j.esci.2025.100408, the study demonstrates how the optimized Ru@C-200 catalyst achieves ultralow overpotentials for both hydrogen evolution and hydrazine oxidation, addressing two critical challenges in sustainable energy systems.

Hydrogen is expected to play a central role in future carbon-neutral energy systems, but conventional water electrolysis faces limitations due to 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 researchers synthesized the ruthenium@carbon material using a pulsed-laser ablation-in-liquid strategy that produced uniform Ru nanospheres encapsulated within graphitic carbon shells, with Ru@C-200 displaying 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. Comprehensive characterization confirmed the fcc-structured metallic Ru core and enhanced ordering of the carbon shell at higher laser energies. In situ analyses revealed that metallic Ru sites are responsible for hydrogen evolution, whereas surface-generated RuOOH species drive hydrazine oxidation, providing mechanistic insight into the catalyst's dual functionality.

When tested in practical applications, a Ru@C-200‖Ru@C-200 pair in a hydrazine-splitting electrolyzer 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, achieving 90% energy efficiency and remaining 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 in integrated systems.

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. Its ability to completely oxidize hydrazine while generating hydrogen positions it 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, potentially accelerating adoption of safer, more efficient hydrogen infrastructures.

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. 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. 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, offering new possibilities for integrated clean-energy technologies and environmental remediation strategies.