Transition metal phosphides (TMPs) have recently emerged as an important type of electrode material for use in supercapacitors thanks to their intrinsically outstanding specific capacity and high electrical conductivity. Herein, we report the synthesis of bimetallic Co x Ni 1−x P ultrafine nanocrystals supported on carbon nanofibers (Co x Ni 1−x P/CNF) and explore their use as positive electrode materials of asymmetric supercapacitors. We find that the Co:Ni ratio has a significant impact on the specific capacitance/capacity of Co x Ni 1−x P/ CNF, and Co x Ni 1−x P/CNF with an optimal Co:Ni ratio exhibits an extraordinary specific capacitance/capacity of 3514 F g −1 /1405.6 C g −1 at a charge/discharge current density of 5 A g −1 , which is the highest value for TMP-based electrode materials reported by far. Our density functional theory calculations demonstrate that the significant capacitance/capacity enhancement in Co x Ni 1−x P/CNF, compared to the monometallic NiP/CNF and CoP/CNF, originates from the enriched density of states near the Fermi level. We further fabricate a flexible solid-state asymmetric supercapacitor using Co x Ni 1−x P/CNF as positive electrode material, activated carbon as negative electrode material, and a polymer gel as the electrolyte. The supercapacitor shows a specific capacitance/capacity of 118.7 F g −1 /166.2 C g −1 at 20 mV s −1 , delivers an energy density of 32.2 Wh kg −1 at 3.5 kW kg −1 , and demonstrates good capacity retention after 10000 charge/discharge cycles, holding substantial promise for applications in flexible electronic devices.

Polymerization rates of N‐vinyl pyrrolidone and corresponding activation energies depend on the nature of the polymerization solvent. This is mainly due to the influence of solvent polarity on the propagation reaction. The dependence of the termination rate on the viscosity of the polymerization medium has a relatively minor effect.

Silicon (Si) has been investigated as a promising photoelectrode material for use in photoelectrochemical water splitting. However, development of Si photocathodes that can operate at a high photocurrent density for solar-driven hydrogen production with long-term stability remains challenging. Herein, we report the fabrication of inverted pyramid textured p-Si photocathodes covered conformally and continuously with a thicknessgradient cobalt phosphide (Co 2 P) layer, which not only effectively isolates p-Si from aqueous electrolyte to avoid corrosion but also efficiently catalyzes the solar-driven hydrogen evolution reaction (HER). Thanks to the unique inverted pyramid structure, the dropcast Co 2 P can distribute all over the p-Si photocathode and form a macroscopically continuous but locally nonuniform layer on the sidewalls of each inverted pyramid. The local nonuniform distribution enables light absorption to be partially separated from catalytic activity. Consequently, the as-fabricated Co 2 P-coated p-Si photocathode exhibits a high photocurrent density of 35.2 mA cm −2 at 0 V versus the reversible hydrogen electrode under AM 1.5G illumination and can photoelectrochemically catalyze the HER above 30 mA cm −2 at least 150 h without notable degradation.

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All solid state batteries are essential candidate for miniaturizing the portable electronics devices.