Recently, Professors Jiang Qing and Yang Chuncheng from the College of Materials Science and Engineering, Jilin University have achieved new advances in the field of electrocatalytic water splitting. The corresponding research paper, entitled Heterogeneous interface and vacancy engineering contribute to metastable catalysts for overall water splitting, was published in Acta Materialia, 2025, 289, 120934.

Developing high-efficiency and low-cost electrocatalysts for water splitting is critical to advancing green hydrogen production. Although metastable catalysts exhibit outstanding catalytic activity toward water splitting, their practical application is severely restricted by facile phase transformation and complicated synthetic procedures, leading to unsatisfactory stability and practicability.

To address the above bottlenecks, a thermal shock strategy was adopted in this work to fabricate self-supported electrodes consisting of Co/Fe co-doped metastable hexagonal close-packed (hcp) Ni/NiO heterostructures with abundant oxygen vacancies grown on nickel foam substrates. Multiple characterizations including X-ray diffraction, spherical aberration-corrected transmission electron microscopy and electron paramagnetic resonance spectroscopy verify that the self-supported electrode possesses metastable hcp Ni crystals, robust heterointerfaces between hcp Ni and face-centered cubic (fcc) NiO, and plentiful oxygen vacancies distributed throughout the material. In addition, in-situ Raman spectroscopy was employed to deeply reveal the dynamic reaction mechanism on catalyst surfaces.

Figure 1. Microstructural characterizations and in-situ Raman spectra of the self-supported electrode.

The unique electron configuration and high-energy state of metastable hcp Ni accelerate rapid electron transport and generate abundant active sites, drastically boosting electrocatalytic reaction kinetics. The construction of heterostructures not only modulates the electronic structure and improves intrinsic catalytic activity, but also greatly enhances the structural durability of metastable catalysts. Meanwhile, Co/Fe dual doping and oxygen vacancy engineering optimize the band structure and electron conductivity of the catalyst, as well as tune the adsorption/desorption energy of reaction intermediates, which further elevates electrocatalytic performance. Benefiting from the above synergistic effects, the anion exchange membrane electrolyzer assembled with this electrode delivers current densities of 10 mA cm⁻² and 1.0 A cm⁻² at low cell voltages of only 1.48 V and 2.55 V, respectively, together with remarkable long-term cycling stability.

Figure 2. Electrochemical performance of anion exchange membrane electrolyzers equipped with the self-supported electrode