Electrocatalytic water splitting is considered an effective way to produce clean hydrogen in a sustainable and eco-friendly manner. However, the anodic oxygen evolution (OER) of water electrolysis is a complex four-electron transfer process with slow kinetics, which limits the overall efficiency of hydrogen production by water electrolysis. ***-based catalysts such as RuO2 and IRO2 exhibit excellent OER catalytic performance, but their scarcity and high cost limit their large-scale application in water electrolysis. Therefore, it is of great significance to develop efficient and cost-effective non-optimal electrocatalysts to promote the practical application of water electrolysis hydrogen production technology.
Recently,Du Xing, Wuhan University of Science and TechnologywithDong Jichen, Institute of Chemistry, Chinese Academy of SciencesA simple method for the preparation of a series of bimetallic C-Mofs (NixFe1-X-THQ, THQ=tetrahydroxy-1,4-benzoquinone hydrate) using a minimal phenyl ligand with a high-density catalytic active site was reported. By adjusting the ratio of Ni Fe, a series of catalysts with the best electronic structure, intermediate adsorption capacity and fast charge transfer rate were obtained.
The experimental results show that the optimal Ni05fe0.The OER overpotential of the 5-THQ catalyst is only 272 mV at a current density of 10 mA cm2, and the catalyst has an OER overpotential of 1There was no significant decrease in activity after continuous operation for 40 hours under 5 VRHE, and the morphology and structure of the material did not change after the reaction, indicating that Ni05fe0.5-Thq exhibits excellent stability (this remarkable electrochemical stability can be attributed to the strong chelation of the coordination bonds between Ni, Fe, and ThQ).
A series of spectroscopic characterizations and theoretical calculations show that Fe3+ (T2G3EG2) can achieve weak electronic interaction with the bridging O due to its high spin valence electron configuration and the corresponding three unpaired electrons in the symmetry (T2G) D orbital, while Ni2+ (T2G6EG2) can achieve strong E-E repulsion with the bridging O because it has a completely symmetric (T2G) D-orbital.
Therefore, when Ni2+ is coupled to Fe3+, the strong E-E repulsion between O2- and Ni2+ will trigger partial electron transfer from Ni2+ to Fe3+, which will well modulate the electronic configuration of the Ni site in NixFe1-X-Thq, so that the binding strength between the Ni site and the adsorbed oxygen species can be optimized to meet the Sabatier principle.
In addition, with the decrease of electron density, Ni2+ with low half-full EG orbital forms appropriate bonding with the adsorbed oxygen species, which is conducive to improving the catalytic activity and accelerating the OER reaction rate. In conclusion, this work provides guidance for the construction of bimetallic C-MOFS electrocatalysts with more high-density catalytic active centers to achieve efficient water electrolysis, and also provides new ideas for the design and research of MOFs electrocatalysts.
regulating electronic structure of bimetallic nife-thq conductive metal–organic frameworks to boost catalytic activity for oxygen evolution reaction. advanced functional materials, 2023. doi: 10.1002/adfm.202310902