Status review of nickel phosphides for hybrid supercapacitors

Recent advances in biopolymers-based carbon materials for supercapacitors

Supercapacitors as potential candidates for novel green energy storage devices demonstrate a promising future in promoting sustainable energy supply, but their development is impeded by limited energy density, which can be addressed by developing high-capacitance electrode materials with efforts. Carbon materials derived from biopolymers have received much attention for their abundant reserves and environmentally sustainable nature, rendering them ideal for supercapacitor electrodes. However, the limited capacitance has hindered their widespread application, resulting in the proposal of various strategies to enhance the capacity properties of carbon electrodes. This paper critically reviewed the recent research progress of biopolymers-based carbon electrodes. The advances in biopolymers-based carbon electrodes for supercapacitors are presented, followed by the strategies to improve the capacitance of carbon electrodes which include pore engineering, doping engineering and composite engineering. Furthermore, this review is summarized and the challenges of biopolymer-derived carbon electrodes are discussed. The purpose of this review is to promote the widespread application of biopolymers in the domain of supercapacitors.

Metal-organic framework-mediated construction of confined ultrafine nickel phosphide immobilized in reduced graphene oxide with excellent cycle stability for asymmetric supercapacitors

Transition metal phosphides (TMPs) with unique metalloid features have been promised great application potential in developing high-efficiency electrode materials for electrochemical energy storage. Nevertheless, sluggish ion transportation and poor cycling stability are the critical hurdles limiting their application prospects. Herein, we presented the metal-organic framework-mediated construction of ultrafine Ni₂P immobilized in reduced graphene oxide (rGO). Nano-porous two-dimensional (2D) Ni-metal-organic framework (Ni-MOF) was grown on holey graphene oxide (Ni(BDC)-HGO), followed by MOF-mediated tandem pyrolysis (carbonization and phosphidation; Ni(BDC)-HGO-X-P, X denoted carbonization temperature and P represented phosphidation). Structural analysis revealed that the open-framework structure in Ni(BDC)-HGO-X-Ps had endowed them with excellent ion conductivity. The Ni₂P wrapped by carbon shells and the PO bonds linking between Ni₂P and rGO ensured the better structural stability of Ni(BDC)-HGO-X-Ps. The resulting Ni(BDC)-HGO-400-P delivered a capacitance of 2333.3 F g^-1 at 1 A g^-1 in a 6 M KOH aqueous electrolyte. More importantly, Ni(BDC)-HGO-400-P//activated carbon, the assembled asymmetric supercapacitor with an energy density of 64.5 Wh kg^-1 and a power density of 31.7 kW kg^-1, almost maintained its initial capacitance after 10,000 cycles. Furthermore, in situ electrochemical-Raman measurements were exploited to demonstrate the electrochemical changes of Ni(BDC)-HGO-400-P throughout the charging and discharging processes. This study has further shed light on the design rationality of TMPs for optimizing supercapacitor performance.