Multistage interfacial engineering of 3D carbonaceous NiP nanospheres/nanoflowers derived from Ni-BTC metal-organic frameworks for overall water splitting.

The regulation of the multi-dimensional interface plays an important role in optimizing the electron transport and gas mass transfer during catalysis, which is conducive to promoting the electrocatalytic process. Herein, a self-supporting electrode has been developed with the multistage interface within 3D NiP@C nanospheres/nanoflowers arrays derived from metal-organic frameworks (MOFs) as template skeletons and precursors. The constructed nanosphere interface protrudes outward to optimize the contact with the electrolyte while the nanoflower lamellar connection promotes rapid electron transfer and exposes more active sites, and accelerates the gas diffusion with the abundant interspace channels. According to theoretical calculation, the synergistic effect between NiP and C is conducive to the optimal adsorption and desorption of H*, thus contributing to the improvement of catalytic kinetics. With the optimized growth times assembled onto nickel foam substrates, the NiP@C-12 h requires overpotentials of only 69 mV and 205 mV to drive the current density of 10 mA cm towards hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), respectively. And it reveals an ultralow cell voltage of 1.55 V at 10 mA cm to achieve overall water splitting (OWS). In addition, the stability of the NiP@C/NF electrocatalyst emerges as prominent long-term stability, which is attributed to the carbonaceous nanosphere anchors on the substrate to minimize the possibility of oxidation of the catalyst surface. This strategy of in situ growth of MOF-derived phosphates provides a general idea for interfacial engineering modification of OWS electrode materials.