Hydrogen production via electrochemical water splitting powered by renewable electricity is a critical process for a sustainable hydrogen economy.
Advancing alkaline water electrolysis (ALKWE) to achieve ampere-level current densities with reduced energy consumption is a central objective. However, this goal is hindered by the trade-off between activity and stability in the hydrogen evolution reaction (HER), which is exacerbated by violent hydrogen bubble evolution at high current densities. These bubbles disturb mass transport, block active sites, and cause catalyst layer peeling.
An atomic-to-macroscale assembled Ni/MoO2 electrode for alkaline water electrolysis (Image by JIANG Shang)
In a study published in the Journal of the American Chemical Society, a team led by Prof. DENG Dehui, Associate Prof. LIU Yanting, and Prof. YU Liang from the Dalian Institute of Chemical Physics (DICP) of the Chinese Academy of Sciences (CAS) proposed an atomic-to-macro multiscale electrode design strategy. By constructing monolithic electrodes with hierarchical porous structures, the team achieved high-efficiency and long-life hydrogen production at ampere-level current densities.
The team constructed a monolithic electrode (Ni/MoO2) featuring abundant atomic heterointerfaces and tri-scale (nano-micro-macro) porosity. This was achieved through the in situ growth of Ni nanoparticle-anchored MoO2 onto a porous Ni framework prepared via powder metallurgy.
The team found that the electrode exhibits a triple-enhancement effect in water electrolysis. First, the interfacial electron transfer from Ni to MoO2 moderately weakens H* adsorption and promotes H2 desorption, thereby enhancing intrinsic activity. Second, the tri-scale hierarchical porosity, together with the hydrophilic MoO2 coating, accelerates bubble detachment and promotes electrolyte permeation, improving mass transfer. Finally, the strong interactions between Ni and MoO2, along with their robust integration onto the electrode skeleton, enhance structural stability.
As a result, the electrodeachieves an overpotential of 145 mV at 1 A cm-2 in 1 M KOH—lower than the 300 mV required for commercial Pt/C catalysts—while maintaining stable operation for over 3,500 hours. In practical alkaline electrolyzer tests, it achieves a cell voltage of 1.80 V with an energy consumption of 4.3 kWh Nm-3 H2 at 1 A cm-2 under industrial conditions (30 wt% KOH at ≥ 85 °C), 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 tradeoff, providing an important advancement for sustainable hydrogen production," said Prof. DENG.