A facile bottom-up strategy based on combustion-reduction toward monolithic micron/nanoporous nickel: An efficient electrode material for hydrogen evolution reaction and supercapacitor

•A monolithic micron-nano porous nickel was created via a bottom-up strategy.•The pore-enriched Ni powders are achieved via a combustion-reduction approach.•The designed MNPN can serve as a high-performance electrode for HER.•The MNPN is used as an efficient current collector for supercapacitor electrodes. Micron/nanoporous metals are of great importance in catalysis, sensor, and energy technologies. However, their practical application is limited because the existing fabrication approaches mainly depend on the top-down strategy, such as dealloying and template methods, which often require an introduction of sacrificial materials and an elaborate process. Herein, the Ni powders with a unique micron/nanoporous structure are achieved via a direct decomposition and reduction of NiNO3 precursor in the combustion flame. The prepared powders are applied to form monolithic micron/nanoporous nickel (MNPN) through a simple dry-press and heating treatment. The designed MNPN can serve as a robust self-supporting electrode for hydrogen evolution reaction, exhibiting a high catalytic activity with the current density of 10 mA cm−2 at overpotentials of 63 mV in 1.0 M KOH and 89 mV in 1.0 M phosphate buffer solution (PBS). Furthermore, the MNPN is also used as an efficient current collector for MNPN-MnO2 supercapacitor electrodes. The MNPN-MnO2 electrodes show a high specific capacitance of 970 F g−1 at 2 mV s−1 and outstanding electrochemical stability with retention of 103.6% after 10,000 cycles. Importantly, the work offers a reliable avenue to develop monolithic micron/nano-scale porous metals for a wide range of applications. [Display omitted]