Hydrogen production through electrochemical water splitting powered by renewable electricity is a critical process for building a sustainable hydrogen economy.

Advancing alkaline water electrolysis (ALKWE) to achieve ampere-level current densities with reduced energy consumption is a key objective. However, this goal is hindered by the inherent trade-off between activity and stability in the hydrogen evolution reaction—a challenge exacerbated by the violent evolution of hydrogen bubbles at high current densities. These bubbles disrupt mass transport, block active sites, and lead to catalyst layer peeling.

To address these challenges, a research team from the Dalian Institute of Chemical Physics (DICP) of the Chinese Academy of Sciences (CAS) has proposed an atomic-to-macro multiscale electrode design strategy. By constructing monolithic electrodes with hierarchical porous structures, the team has achieved high-efficiency and long-life hydrogen production at ampere-level current densities.

Their findings were recently published in Journal of the American Chemical Society.

The team developed a monolithic Ni/MoO₂ electrode featuring abundant atomic heterointerfaces and tri-scale (nano-micro-macro) porosity. This was realized through the in situ growth of Ni nanoparticle-anchored MoO₂ onto a porous Ni framework prepared via powder metallurgy.

The researchers found that the electrode exhibits a triple-enhancement effect in water electrolysis. First, interfacial electron transfer from Ni to MoO₂ moderately weakens H* adsorption and promotes H₂ desorption, thereby boosting intrinsic activity. Second, the tri-scale hierarchical porosity, combined with the hydrophilic MoO₂ coating, accelerates bubble detachment and facilitates electrolyte permeation, improving mass transfer efficiency. Finally, strong interactions between Ni and MoO₂, along with their robust integration into the electrode skeleton, enhance structural stability.

As a result, the electrode achieves an overpotential of 145 mV at 1 A cm^-2 in 1 M KOH—significantly lower than the 300 mV required for commercial Pt/C catalysts—while maintaining stable operation for more than 3,500 hours. In practical alkaline electrolyzer tests under industrial conditions (30 wt% KOH at ≥ 85 °C), the electrode achieves a cell voltage of 1.80 V with an energy consumption of 4.3 kWh Nm^-3 H₂ at 1 A cm^-2, with operational durability exceeding 1,000 hours.

"This atomic-to-macro multiscale electrode design strategy overcomes the long-standing dilemma in high-current-density ALKWE caused by the activity-stability trade-off, providing an important advancement for sustainable hydrogen production," said Prof. DENG Dehui, a corresponding author of the study.

An atomic-to-macroscale assembled Ni/MoO₂ electrode for alkaline water electrolysis. (Image by JIANG Shang)