Qianqiao Chen

CoFe-based materials are considered promising bifunctional catalysts for overall water splitting due to multicomponent synergistic effects. However, the unrestricted mobility of metal atoms during high-temperature synthesis often leads to particle aggregation and coarsening, which can block active sites and impede the precise modulation of electronic structures. This severely limits their HER/OER catalytic activity and long-term stability. To address these issues, this study proposes a spatial confinement strategy using ZIF as both a precursor and a confinement framework. This approach effectively suppresses the disordered agglomeration of CoFe nanoparticles and exposes more active sites. Further combining carbonization and in-situ nitridation modification, a composite system of CoFe metal nitride and N-doped carbon was prepared, significantly improving the kinetic properties of HER and OER. The CoFe composite catalyst achieves the optimal overpotential of 85 mV for the HER at 10 mA·cm-2, and 273 mV for the OER at 50 mA·cm-2. The assembled overall water splitting system requires only 1.59 V at a working current of 10 mA·cm-2, and can operate stably for 12 hours at 50 mA·cm-2. This study provides a feasible approach to solving the particle aggregation problem of CoFe alloy-based catalysts, thereby enhancing their application prospects in the field of electrocatalysis.

Exposing catalytically active sites and modulating the electronic structure of active metals are key strategies for enhancing oxygen evolution reaction (OER) performance. Leveraging the tunable interlayer anions in layered double hydroxides, we developed a scalable synthesis of high-performance OER catalysts consisting of FeNiCo spinel oxide and high-valence metal oxides (MoO₃, WO₃, CrO₃, V₂O₅). This approach integrates separate nucleation/aging steps, transition-metal oxyanion intercalation, and thermal oxidation. The resulting defect-rich ultrathin oxide nanosheets precisely regulate the electronic structure of active sites, shifting the rate-determining step (O* → OOH*) to improve the OER thermodynamics. These catalysts outperform commercial RuO₂ in both activity and stability. Remarkably, FeNiCoO₄/MoO₃ achieves a current density of 50 mA cm^-2 at an overpotential of just 238 mV with a Tafel slope of 41.12 mV dec^-1, exceeding all reported powder-based oxide OER catalysts. It also demonstrates an excellent 100 h stability at 50 mA cm^-2. This work provides a universal and scalable platform for designing efficient OER electrocatalysts.

A high-entropy strategy can promote the electrocatalytic activity of catalysts through a synergistic electronic environment. In this work, a high-entropy FeCoNiCrCe LDH was in situ constructed on a nickel foam substrate via facile pulse current (PC) electrodeposition at room temperature in just 20 minutes. This electrode outperforms its counterpart prepared by direct current (DC) electrodeposition, with a low overpotential of 215 mV at 10 mA cm⁻² and a small Tafel slope of 45.15 mV dec⁻¹. Notably, it exhibited remarkable stability during a 7-day chronopotentiometric test at 50 mA cm⁻². The enhancements arise not only from the synergistic effect of five-metal composition, but more importantly, from the microstructural advantages of the PC-prepared electrode, which are revealed from a novel perspective by comparison with its DC-prepared counterpart electrode. which are revealed from a novel perspective by comparison with its DC-prepared electrode, which served as the counterpart. The optimized surface morphology with uniform element distribution and similar content by PC electrodeposition enables more effective electronic structure modulation of the active sites by Cr and Ce in the local micro-region. Moreover, the near-equal element composition in FeCoNiCrCe is conducive to increasing the configuration entropy, making the high-entropy stabilization effect more pronounced, thereby leading to enhanced structural stability and OER durability compared to the DC counterpart.

A defect-rich CrNiCoO ₄ /MoO ₃ heterostructure was constructed via a multi-step strategy, achieving exceptional OER activity (260 mV@50 mA cm ⁻² ) and efficient overall water splitting (2.00 V@100 mA cm ⁻² ), outperforming the noble-metal benchmark.

Urea oxidation reaction (UOR) is an attractive alternative anodic reaction to oxygen evolution reaction (OER) for its low thermodynamic potential (0.37 V vs RHE). A major challenge that prohibits its practical application is the six-electron transfer process during UOR, demanding enhancements in the catalytic activity. Herein, a Fe-doped Ni3S2 catalyst with a uniform flower-like structure is synthesized in situ on nickel foam via a simple one-step hydrothermal method. The electrochemical properties of Fe-Ni3S2 are significantly improved since a current density of 10 mA cm-2 only requires a 1.33 V potential and remains stable for 60 h. The structural characterization demonstrates a strong interaction between Fe and Ni3S2. After Fe doping, the active site increases, which promotes the formation of NiOOH on the catalyst surface, thus speeding up the UOR process. These changes are beneficial to charge transfer and optimize the adsorption energy of the intermediates. In situ EIS further confirms that Fe promotes electron transfer during the UOR process, reduces the interface resistance between the catalyst and the electrolyte, and lowers the driving voltage.