Transition Metal (Mn, Fe, Ni) Doping of ZIF-67 for Enhanced Electrocatalytic Performance in Water Splitting

Electrocatalytic water splitting offers a viable route to sustainable hydrogen generation, yet the development of non-noble metal catalysts that combine high efficiency with long-term stability remains a significant hurdle. Zeolitic imidazolate framework-67 (ZIF-67) has emerged as a potential electrocatalyst, but its activity is often limited by insufficient active sites and poor conductivity. In this study, Mn, Fe, and Ni doped derivatives of ZIF-67 (ZIF-67/M, M = Mn, Fe, Ni) were synthesized via a post-synthetic modification method to improve the electrocatalytic performance. The effects of metal doping on structure, morphology, and water splitting activity were systematically investigated. XRD and FTIR confirmed the successful incorporation of heteroatoms without destroying the crystalline framework, while TGA revealed altered thermal stability. BET measurements showed a transformation from microporous to mesoporous structures upon doping, and SEM exhibited crystal distortion, aggregation, and increased surface roughness. Electrochemical tests demonstrated that doping significantly enhanced both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) performances. At 10 mA cm−2, ZIF-67/Fe exhibited the lowest overpotentials for OER (271 mV) and HER (338 mV), outperforming ZIF-67/Mn, ZIF-67/Ni, and pristine ZIF-67. Overall water splitting tests on ZIF-67/Fe showed negligible overpotential change after 24 h, confirming good ambient stability. In summary, metal doping effectively enhances the electrocatalytic water splitting performance of ZIF-67 by modulating its coordination environments and active site distribution, with ZIF-67/Fe exhibiting the best overall performance as a promising bifunctional electrocatalyst.