Holistically Improving the Process of Producing Hydrogen from Water

Schematic illustration of the auxiliary-driving effect, highlighting its role in accelerating the HER process.
Image Credit: ©Hao Li et al.

Scientific Frontline: "At a Glance" Summary

• Main Discovery: Researchers developed a novel catalyst combining ruthenium and vanadium dioxide that simultaneously optimizes both water dissociation and hydrogen gas formation in alkaline water electrolysis.
• Methodology: The team employed an auxiliary-driving strategy to engineer the interface between ruthenium active sites and vanadium dioxide, forming conjugated pi-bonds and leveraging a reversible hydrogen spillover process to dynamically adjust electronic structures during the reaction.
• Key Data: The new catalyst demonstrated an overpotential of 12 millivolts at 10 milliamperes per square centimeter and a turnover frequency of 12.2 per second, indicating higher hydrogen evolution activity than conventional platinum-carbon and ruthenium-carbon catalysts.
• Significance: This approach overcomes the kinetic imbalances typical in anion exchange membrane water electrolysis by coordinating multiple reaction steps simultaneously, enabling highly efficient hydrogen production with minimal energy loss.
• Future Application: The highly durable catalyst design has the potential to lower the cost of green hydrogen production, supporting its broader integration into steel production, chemical manufacturing, commercial shipping, and large-scale renewable energy storage.
• Branch of Science: Materials Science and Electrochemistry
• Additional Detail: Device-level performance improvements were confirmed using distribution of relaxation time analysis, and the resulting experimental and computational data have been openly uploaded to the Digital Catalysis Platform.

Synthesis and Structural Elucidation of the Ru/VO2-CNFs.
Image Credit: ©Hao Li et al.

Producing clean hydrogen from water is often compared to storing renewable energy in chemical form, but improving the efficiency of that process remains a scientific challenge. Researchers at Tohoku University have now developed a catalyst design that helps hydrogen form more smoothly under alkaline conditions, a key step toward practical green hydrogen production.

Hydrogen generation in alkaline water electrolysis depends on the hydrogen evolution reaction (HER). In anion exchange membrane water electrolysis (AEMWE), this reaction involves two tightly connected steps: splitting water molecules and forming hydrogen gas. If either step slows down, overall performance suffers.

Many existing catalysts improve only one of these steps. Only a partial increase in efficiency can have a detrimental impact on overall output. It is similar to an assembly line where one worker moves faster but the next cannot keep up. To address this imbalance, the research team focused on coordinating both steps at the same time.

The researchers proposed an auxiliary-driving strategy that combines ruthenium (Ru) with vanadium dioxide (VO₂). By surrounding Ru active sites with VO₂, the catalyst is designed to consecutively optimize both the water dissociation step (Volmer step) and the hydrogen formation step (Heyrovsky step).

At the interface between Ru and VO₂, the formation of V-O-Ru conjugated π-bonds dynamically adjusts the electronic structure of the active sites. This promotes faster water dissociation. At the same time, a reversible hydrogen spillover process helps regulate hydrogen adsorption, bringing the catalyst closer to optimal reaction conditions predicted by microkinetic models.

a) Differential charge density difference of Ru/VO2-CNFs and Ru-CNFs, where yellow and blue regions indicate charge accumulation and depletion, respectively. (b) Gibbs free energy diagram for the alkaline HER process with the corresponding TS shown in the inset. (c) H* structures at different sites during hydrogen spillover progress. (d) Energy barrier for the hydrogen spillover process. (e) PDOS of OH-H state for Ru/VO2-CNFs. (f) PDOS of OH+H state for Ru/VO2-CNFs. (g) Plots of hydrogen desorption peak positions versus scan rates for Ru/VO2-CNFs, Ru-CNFs, Pt/C, and Ru/C. (h) 2D microkinetic volcano of HER as a function of (ΔGH∗, ΔGOH∗), simulated under alkaline conditions.
 Image Credit: ©Hao Li et al.

Under identical testing conditions, the new catalyst showed higher hydrogen evolution activity than conventional Ru/C and Pt/C catalysts. It achieved an overpotential of 12 mV at 10 mA cm⁻² and a turnover frequency of 12.2 s⁻¹, indicating efficient hydrogen production with low energy loss.

The team also evaluated the catalyst in a working AEMWE device. Using distribution of relaxation time (DRT) analysis, they confirmed that the improved reaction kinetics observed in laboratory tests translated to device-level performance.

"This auxiliary-driving concept allows us to coordinate multiple reaction steps rather than optimizing them separately," said Yizhou Zhang, associate professor at Tohoku University's Advanced Institute for Materials Research. "By engineering the interface between Ru and VO₂, we can improve overall reaction kinetics in alkaline hydrogen evolution."

More efficient and durable electrolyzers can reduce the electricity required to produce hydrogen and extend system lifetime. Lowering the cost of green hydrogen could support its broader use in sectors such as steel production, chemical manufacturing, shipping, and large-scale energy storage. The researchers plan to further refine the interfacial structure and explore whether the auxiliary-driving strategy can be applied to other catalytic systems.

All the key experimental and computational data are also uploaded to the Digital Catalysis Platform, the largest catalysis database to date developed by the Hao Li Lab.

Resource material: Digital Catalysis Platform

Published in journal: ACS catalysis

Title: Stepwise Acceleration of Water Dissociation and Hydrogen Spillover for Enhanced Overall Alkaline Hydrogen Evolution

Authors: Tingyu Lu, Jing Li, Caikang Wang, Heng Liu, Songbo Ye, Xue Jia, Linda Zhang, Di Zhang, Dongmei Sun, Yanhui Gu, Qiang Wang, Bo Da, Li Wei, Yizhou Zhang, Hao Li, and Yawen Tang

Source/Credit: Tohoku University

Reference Number: ms021926_01

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