Binary transition metal phosphides hold immense potential as innovative electrode materials for constructing high-performance energy storage devices. Herein, porous binary nickel–cobalt phosphide (NiCoP) nanosheet arrays anchored on nickel foam (NF) were rationally designed as self-supported binder-free electrodes with high supercapacitance performance. Taking the combined advantages of compositional features and array architectures, the nickel foam supported NiCoP nanosheet array (NiCoP@NF) electrode possesses superior electrochemical performance in comparison with Ni-Co LDH@NF and NiCoO₂@NF electrodes. The NiCoP@NF electrode shows an ultrahigh specific capacitance of 2143 F g⁻¹ at 1 A g⁻¹ and retained 1615 F g⁻¹ even at 20 A g⁻¹, showing excellent rate performance. Furthermore, a binder-free all-solid-state asymmetric supercapacitor device is designed, which exhibits a high energy density of 27 W h kg⁻¹ at a power density of 647 W kg⁻¹. The hierarchical binary nickel–cobalt phosphide nanosheet arrays hold great promise as advanced electrode materials for supercapacitors with high electrochemical performance.

We found that Ni(OH) ₂ nanosheets of Ni(OH) ₂ /NOSCF decorated with ∼3.3 nm CeO ₂ NPs displayed enhanced OER performance.

Coal based nanofibers were prepared by electrospinning a mixture of polyacrylonitrile and acid treated coal. Coal based activated carbon fibers were further obtained by carbonization and steam activation. The effects of acid treatment on raw coal were studied to explain the enhanced solubility in various solvents. The solubility of coal was as high as 6.6 wt% in N,N-dimethylformamide. The electrochemical performance of supercapacitor electrodes using coal based activated carbon fiber mats was then studied. This binder-free electrode showed a specific capacitance of 230 F g⁻¹ at a current density of 1 A g⁻¹ and an excellent capacity retention of 97% after 1000 cycles.

A one-pot hydrothermal route was developed for the preparation of nitrogen-doped graphene (NG) hydrogels using graphene oxide (GO) as a raw material and nine amino acids with different acidities (acidic, neutral and basic) as doping agents. The morphology, structure and composition of the prepared NG using three amino acids (DL-aspartic acid, acidic; L-glycine, neutral; L-arginine, basic) were characterized by SEM, nitrogen physisorption, Raman and XPS spectroscopy. Acidic amino acids yielded NG with a cross-linked 3D network with a large specific surface area of 367.1 m² g⁻¹, while NG arising from the use of basic amino acids showed a tightly stacked structure with a much smaller surface area of 10.5 m² g⁻¹. The charged amino acids, and the ensuing electrostatic interactions between the amino acid and GO, affect the morphology of NG, and ultimately affect its electrochemical performance. The samples prepared using acidic amino acids, with the lowest surface N content (1.0%) but the largest surface area, displayed high specific capacitance of 246 F g⁻¹ at 3 A g⁻¹. The microstructure, surface area and effective nitrogen content, mainly the pyridinic nitrogen group related to pseudocapacitance, play important roles in the capacitive performance of the NG samples.