Boosting oxygen evolution reaction performance on NiFe‑based catalysts through d‑orbital hybridization

Electrochemical water splitting is one of the most promising approaches to sustainable hydrogen production, yet the sluggish oxygen evolution reaction (OER) on the anode side remains a persistent bottleneck. Addressing this challenge, a research team led by Prof. Haifeng Bao at Wuhan Textile University, in collaboration with Wuhan University, has developed a novel NiFe-based catalyst that employs 5d lanthanum doping to precisely engineer the electronic structure of the active site—achieving unprecedented efficiency and durability through tailored d-orbital coupling.

The new catalyst, termed NiFeLa, was synthesized using a simple electrodeposition technique, where La atoms are incorporated into the NiFe alloy framework to form asymmetric La–NiFe coordination environments. This structural distortion optimizes the d-band center and enhances d–p orbital hybridization with oxygen-containing intermediates. As a result, the catalyst exhibits superior OER kinetics, characterized by a low overpotential of 190 mV at 10 mA cm^-2 and an outstanding Tafel slope of only 34.3 mV dec^-1.

High-resolution STEM, XAS, and XPS analyses revealed that La doping disrupts the symmetry of NiFe sites, resulting in localized electronic heterogeneity and lattice strain. These factors collectively enhance the adsorption strength of key intermediates like *OOH and *OO species while lowering the energy barrier of the rate-determining step in the OER pathway. Notably, in situ UV–Vis spectroelectrochemical analysis confirmed the earlier onset of oxygen intermediate formation for NiFeLa compared to its undoped counterpart, consistent with a lattice oxygen-mediated (LOM) mechanism.

The catalyst also shows exceptional long-term durability, maintaining stable operation for over 600 hours at 100 mA cm^-2 in alkaline electrolyte. Electrochemical impedance spectroscopy (EIS) revealed significantly reduced charge transfer resistance and superior interfacial conductivity, further confirming the improved catalytic kinetics. In terms of electrochemical surface area (ECSA), NiFeLa displayed a large double-layer capacitance, indicating abundant active sites.

Importantly, the practical utility of NiFeLa was demonstrated in an anion exchange membrane water electrolyzer (AEMWE). The assembled device achieved a cell voltage of just 1.58 V at 1 A cm^-2, outperforming commercial RuO₂-based systems and operating stably for more than 600 hours. These metrics position NiFeLa among the most promising non-precious metal OER catalysts for real-world water electrolysis systems.

Density functional theory (DFT) calculations corroborated the experimental findings, showing that La doping elevates the d-band center and reduces antibonding electron density, leading to stronger metal–oxygen interactions. Interestingly, the study also found that excessive La content may compromise catalyst stability due to increased surface energy—highlighting the importance of optimized doping concentrations.

By successfully integrating orbital-level engineering with practical electrochemical performance, the NiFeLa catalyst represents a milestone in the design of earth-abundant, high-performance materials for green hydrogen technologies. It exemplifies how fine-tuning electronic structure and breaking local symmetry can dramatically reshape catalytic activity and stability.

This work paves the way for next-generation electrolyzers that are both efficient and affordable, offering a viable path toward scaling up green hydrogen production in support of global decarbonization goals.