The development of self-charging supercapacitor power cells (SCSPCs) has profound implications for smart electronic devices used in different fields. Here, we epitaxially electrodeposited Mo- and Fe-codoped MnO2 films on piezoelectric ZnO nanoarrays (NAs) grown on the flexible carbon cloth (denoted ZnO@Mo-Fe-MnO2 NAs). An SCSPC device was assembled with the ZnO@Mo-Fe-MnO2 NA electrode and poly(vinylidenefluoride-co-trifluoroethylene) (PVDF-Trfe) piezoelectric film doped with BaTiO3 (BTO) and carbon nanotubes (CNTs) (denoted PVDF-Trfe/CNTs/BTO). The SCSPC device exhibited an energy density of 30 μWh cm-2 with a high-power density of 40 mW cm-2, and delivered an excellent self-charging performance of 363 mV (10 N) driven by both the piezoelectric ZnO NAs and the PVDF-Trfe/CNTs/BTO films. More intriguingly, the device also could also be self-charged by 184 mV due to residual stress alone, and showed excellent energy conversion efficiency and low self-discharge rate. This work illustrates for the first time the self-charging mechanism involving electrolyte ion migration driven by both electrodes and films. A comprehensive analysis strongly confirmed the important contribution of the piezoelectric ZnO NAs in the self-charging process of the SCSPC device. This work provides novel directions and insights for the development of SCSPCs.

The kinetic process of a slow oxygen evolution reaction (OER) always constrains the efficiency of overall water electrolysis for H2 production. In particular, nonprecious metal electrodes for the OER have difficulty simultaneously possessing good electrocatalytic activity and long-term stability in pH-universal media. In this work, urea is first used as a pore-forming agent and active C/N source to fabricate a nanoporous NiFeCoCN medium-entropy alloy (MEA) by high-temperature sintering based on the nanoscale Kirkendall effect. The NiFeCoCN MEA achieves an overpotential of 432 mV at a current density of 10 mA cm-2 and a lower Tafel slope of 52.4 mV dec-1 compared to the IrO2/Ti electrode (58.6 mV dec-1) in a 0.5 M H2SO4 solution. In a 1 M KOH solution, the NiFeCoCN MEA obtains an overpotential of 177 mV for 10 mA cm-2 and a Tafel slope of 36.1 mV dec-1, which is better than IrO2/Ni foam. This work proves a novel strategy to design and prepare nanoporous MEA materials with desirable C/N species, which provides promising prospects for the industrial production of H2 energy.