Electronic regulation of electrochemical reconstruction via a Ce3+/Ce4+ electron buffer for efficient alkaline water splitting.

The rational regulation of electrochemical reconstruction is a promising route to high-performance oxygen evolution reaction (OER) electrocatalysts, yet the underlying electronic mechanisms and their technological relevance remain elusive. Herein, a Ce-doped Ni-based metal organic framework (NiCe NDC) precatalyst is fabricated via a facile one-step solvothermal method. The reversible Ce3+/Ce4+ redox pair acts as a dynamic electron-buffering center, and the strong Ni 3d-O 2p-Ce 4f orbital coupling induces controllable reconstruction into stable β-NiOOH, while inhibiting the over-oxidation and structural deterioration of active phases. In situ Raman spectroscopy and X-ray photoelectron spectroscopy verify the optimized reconstruction kinetics and reversible Ce valence evolution, while density functional theory (DFT) calculations confirm that near-Fermi-level Ce 4f states serve as electron reservoirs to modulate the Ni d-band center, enrich electronic density at the Fermi level, and reduce the free-energy barrier of the rate-determining *O to *OOH step. Optimized NiCe NDC delivers superior alkaline OER performance with a low overpotential of 194 mV at 10 mA cm-2, a small Tafel slope of 61.8 mV dec-1, and long-term stability over 100 h at 100 mA cm-2. Coupled with a Pt/C cathode, the assembled overall water-splitting electrolyzer achieves current densities of 10-1000 mA cm-1 under low cell voltages of 1.42-1.90 V. A techno-economic assessment (TEA) of a 20 MW alkaline electrolyzer estimates a levelized cost of hydrogen (LCOH) of ∼USD 5.40 kg-1H₂. This work reveals the electronic mechanism of rare-earth-regulated reconstruction and provides a feasible strategy for designing advanced OER catalysts toward industrial green hydrogen production.