An alkaline-acid asymmetric electrolyzer using NiCoP/CoP/Co3O4 multi-shell hollow nanoflakes as cathode and Ag as anode to realizing energy efficient production of hydrogen and shape controllable silver oxide

Abstract

Large scale hydrogen generation by water electrolysis is severely impeded by the high cost of noble metal electrode materials and the kinetic-sluggish anodic oxygen evolution reaction (OER). Here we design a MOF-derived NiCoP/CoP/Co3O4 multi-shell hollow nanoflakes as a low-cost cathode electrocatalyst for hydrogen evolution reaction (HER), and replace the OER with more favorable silver oxidation reaction (AOR). The NiCoP/CoP/Co3O4 supported on carbon cloth ([email protected]/CoP/Co3O4) endows an impressive low overpotential (η) of 90 mV at 10 mA cm−2 and a low Tafel slope of 81.7 mV dec−1 for HER in 0.5 M H2SO4 electrolyte. Coupling it with Ag electrode to forming an asymmetric alkali-acid electrolyzer exhibits superior performance with the requirement of a cell voltage of only 1.16 V to attain 10 mA cm−2 with nearly 100% of Faradaic efficiencies for both H2 and Ag2O generation, showing dramatically lower voltage than that previously reported for conventional water splitting systems. In addition, the size and shape of Ag2O can be controlled by manipulating current density. Our electrolyzer design provides not only an economical approach to produce H2 and Ag2O but also shows great promise for expansion into the electrosynthesis of other value-added chemicals.