Boosting alkaline hydrogen evolution and Zn-H2O cell induced by interfacial electron transfer

Directly use of metal-organic frameworks (MOFs) as electrocatalysts by taking the intrinsic advantages of MOFs architecture for water splitting have attracted tremendous interest. Herein, we reported a vapor-phase transformation method to construct well-aligned nickel based MOFs (Ni-MOF) nanoarrays grown on electrochemical exfoliated graphite (EG) foil and further phosphorization treatment to derive a Ni-MOF/Ni2P@EG. In such a hybrid structure, Ni2P with a particle size of similar to 9 nm was encapsulated into Ni-MOF nanorod arrays on EG foil. Profiting from super hydrophilic nature and nanoarray feature, the Ni-MOF/Ni2P@EG hybrid displayed an excellent activity of hydrogen evolution reaction (HER) with low overpotentials of 132 and 233 mV at 10 and 150 mA cm(-2), respectively, as well as a small Tafel slope of 59 mV dec(-1) in alkaline media, which are among the best values in all previously reported MOFs-based hybrid HER electrocatalysts and even outperform commercial Pt/C at high current density (250 mV at 150 mA cm(-2)). The strong coupling effect of the constructed interfaces in this hybrid resulted in an efficient electron transfer from Ni2P to Ni-MOF, which promotes the adsorption of water molecules for accelerating water dissociation step, thus boosting hydrogen generation. Further, this Ni-MOF/Ni2P@EG could be used as cathode in alkaline Zn-H2O cell, reaching a power density of 4.1 mW cm(-2) with high stability to integrate hydrogen production with electricity generation.