MOF-on-MOF in situ-derived hybrid CoNi@C/N-doped C micro-rods arrays as an efficient catalyst for hydrogen evolution reaction in alkaline solution

The development of durable and efficient transition alloy electrocatalysts under alkaline conditions for the hydrogen evolution reaction (HER) is pivotal for various applications in water electrolysis. Metal-organic frameworks (MOFs) are commonly subjected to pyrolysis to produce efficient alloy@carbon electrocatalysts. In this study, leveraging the respective advantages of two MOFs, the bimetallic CoNi embedded in carbon/ nitrogen-doped carbon (CoNi@CNC) arrays have been in-situ synthesized as HER electrocatalysts through annealing a MOF-on-MOF core-shell precursor assembled from MOF-74 and ZIF-67. The MOF-74 derivative has a uniform structure and large porosity except poor conductivity, while ZIF-67 derivative is highly conductive but structurally unstable. As a result, the CoNi@CNC hybrid electrode exhibits a low overpotential of 83 mV at 10 mA/cm2 in alkaline solution, as well as good durability at elevated current densities. It is found that the nitrogendoped carbon shell can modulate the electronic structure of alloy and increase its charge transfer ability, leading to improved electrocatalytic performance. The pure carbon inside maintains the columnar array structure of CoNi, improving the stability of catalyst. This strategy presents a novel approach for synthesizing promising HER electrocatalysts from MOFs for energy conversion technologies.