Three-dimensional “skin-core” structures of FeCe co-doped PPy@FCC-ZIF by in-situ ion exchange etching to used stabilize water electrolysis in high current density

Abstract

As an effective energy storage medium, hydrogen can store large-scale energy. At the same time, hydrogen energy solves the problem of renewable energy volatility and promotes the balanced allocation of energy. In all the hydrogen production methods, the use of electricity to drive water decomposition to produce hydrogen is a sustainable solution. In this paper, using PPy as the active intermediate layer, composite nanoarray electrocatalyst with three-dimensional “skin core” structure was prepared by in-situ growth of Co-ZIF and ion exchange etching of Fe and Ce elements. Among them, the existence of PPy can provide an active site for the growth of Co-ZIF, which improves the unstable situation of electrolysis of self-supporting catalyst based on nanosheet structure under high current density. In addition, the co-doping of Fe and Ce improved the electric field structure of Co-ZIF nanosheets and increased the catalytic activity of the catalyst. The prepared PPy@FCC-ZIF/NF catalysts have a low overpotential of 260 mV, 299 mV and 383 mV at current densities of 50, 200 and 500 mA cm⁻², respectively. Even at the high current density of 1 A cm⁻², the overpotential is only 440 mV. In addition, the electrolytic water system with PPy@FCC-ZIF/NF as anode exhibited stable electrolytic behavior. When using Pt/C as the cathode, the device can electrolysis 125 h with a stable working voltage of 1.70 V at 50 mA cm⁻². When the commercial NiMo/NF catalyst is used as the cathode, it can be stably electrolyzed for 60 h at a high current density of 500 mA cm⁻². This study provides the idea for the research of advanced three-dimensional self-supported electrocatalysts and the possibility for the construction of new commercial electrocatalysts.