Interface-coupling of CoFe-LDH on MXene as high-performance oxygen evolution catalyst

Oxygen evolution reaction (OER) is the bottleneck reaction of the overall water splitting process despite the intensive research in the past decades. Efficient yet stable low-cost OER catalysts have been widely explored but further improvement is still highly demanded. Herein, a type of hybrid OER catalyst was prepared by the growth of CoFe-LDH (layered double hydroxide) on the surface of Ti3C2 MXene nanosheets, which exhibits superior OER performance than the state-of-the-art RuO2. The enhancement of the OER performance could be attributed to the combination of oxygen-breaking ability of CoFe-LDH and metallic conductivity of Ti3C2 MXene substrate. Meanwhile, the direct growth of CoFe-LDH on the hydroxyl-rich surface of MXene effectively prevents itself from aggregation, exposing more CoFe-LDH edge active sites. What's more important is that the intimate interface between CoFe-LDH and Ti3C2 MXene brings in efficient charge transfer and oxygen activation, which is supported by the DFT calculation results. The direct growth of CoFe-LDH on MXene endows the insulating LDH with metallic features with the O 2p states become distributed above the Fermi level which is mediated by the possible anionic redox process. This work demonstrates the great potential of MXene-based hybrid nanostructure for energy conversion applications.