Optimizing active sites <i>via</i> chemical bonding of 2D metal–organic frameworks and MXenes for efficient hydrogen evolution reaction activity

Metal-organic frameworks (MOFs) are promising electrocatalysts due to their large surface areas and abundant metal sites, but their efficacy is limited by poor exposure of active metal atoms to the electrolyte. To address this issue, we report an innovative approach that integrates a conductive layered MXene (Ti₃C₂T_<i>x</i>) with a 2-dimensional (2D) Ni₃(2,3,6,7,10,11-hexaiminotriphenylene)₂-MOF through <i>in situ</i> synthesis of the MOF on the MXene, maximizing the accessible exposure of active sites for electrocatalytic hydrogen evolution reaction (HER) activity. XPS analysis confirms that the MOF is chemically bonded with the MXene layers, while SEM analysis shows complete overlapping, intercalation, and surface growth of the MOF on the MXene layers. The optimized chemically bonded MOF on MXene exhibits superior electrocatalytic activity, with an overpotential of 180 mV in alkaline media-four times better than that of the pristine MOF-and an overpotential of 240 mV in acidic media, three times better than that of the pristine MOF. The enhanced electrocatalytic activity is attributed to the bond formation between Ti atoms from the MXene and N atoms from the MOF, which facilitates charge transfer and improves both the kinetics and active electrocatalytic area for the HER. This method offers a simple, pioneering approach to fabricate noble metal-free, nanostructured electrocatalysts, enhancing water electrolysis efficiency and extending applicability to other conductive MOFs.