Porous nanosheet network architecture of CoP@Ni(OH)2 composites for high performance supercapacitors

Electrochemical Deposition for Cultivating Nano- and Microstructured Electroactive Materials for Supercapacitors: Recent Developments and Future Perspectives

The globe is currently dealing with serious issues related to the world economy and population expansion, which has led to a significant increase in the need for energy. One of the most promising energy devices for the next generation of energy technology is the supercapacitor (SC). Among the numerous nanostructured materials examined for SC electrodes, inorganic nanosheets are considered to be the most favorable electrode materials because of their excellent electrochemical performance due to their large surface area, very low layer thickness, and tunable diverse composition. Various inorganic nanosheets (NS) such as metal oxides, metal chalcogenides, metal hydroxides, and MXenes show substantial electrochemical activity. Herein, a comprehensive survey of inorganic NS arrays synthesized through the electrodeposition method is reported with the discussion on detailed growth mechanism and their application in the fabrication of SC electrodes/devices for powering flexible and wearable electronics appliances. To begin with, the first section will feature the various types of electrodeposition working mechanism, SC types and their working mechanisms, importance of nanosheet structure for SCs. This review gives a profound interpretation of supercapacitor electrode materials and their performances in different domains. Finally, a perspective on NS array through electrodeposition method applications in diverse fields is extensively examined.

Multimetallic transition metal phosphide nanostructures for supercapacitors and electrochemical water splitting

Transition metal phosphides (TMPs) have recently emerged as an important class of functional materials and been demonstrated to be outstanding supercapacitor electrode materials and catalysts for electrochemical water splitting. While extensive investigations have been devoted to monometallic TMPs, multimetallic TMPs have lately proved to show enhanced electrochemical performance compared to their monometallic counterparts, thanks to the synergistic effect between different transition metal species. This topical review summarizes recent advance in the synthesis of new multimetallic TMP nanostructures, with particular focus on their applications in supercapacitors and electrochemical water splitting. Both experimental reports and theoretical understanding of the synergy between transition metal species are comprehensively reviewed, and perspectives of future research on TMP-based materials for these specific applications are outlined.

Ultrathin and Highly Crumpled/Porous CoP Nanosheet Arrays Anchored on Graphene Boosts the Capacitance and Their Synergistic Effect toward High-Performance Battery-Type Hybrid Supercapacitors

Constructing novel electrode materials with supernal specific capacitance and cycle stability is important for the practical applications of supercapacitors. Herein, ultrathin and highly crumpled CoP/reduced graphene oxide (rGO) nanosheet arrays are grown on nickel foam (NF) through a hydrothermal-phosphidation route. Benefitting from the synergistic effects of CoP with large specific capacity and rGO with high conductivity and ultrathin nanosheet arrays structure, CoP/rGO shows extraordinary electrochemical performance. The CoP/rGO electrode possesses a superior specific capacity of 1438.0 C g^-1 (3595.0 F g^-1) at 1 A g^-1, which is 3.43, 2.05, and 2.26 times larger than those of Co(OH)₂/rGO, Co₃O₄/rGO, and bare CoP. In particular, the CoP/rGO nanosheet arrays show the highest specific capacities among the monometallic phosphide-based nanostructures reported so far. The CoP/rGO retains 1198.9 C g^-1 (2997.2 F g^-1) at 10 A g^-1, revealing the outstanding rate capability of 83%. Theoretical calculations reveal that rGO can adequately reduce the absorption energy of OH^- on CoP, which makes CoP/rGO have strong adsorption capacity of OH^-, resulting in boosting electrochemical performance. A hybrid supercapacitor of CoP/rGO/NF//AC was designed, which presents a superior energy density of 43.2 Wh kg^-1 at a power density of 1010.5 W kg^-1. After 10 000 cycles, the CoP/rGO/NF//AC supercapacitor reveals excellent cycling durability with a capacitance retention of 89%. This work provides a new insight into the design of high-performance electrode materials by combining high capacitive metal phosphides with conductive carbon, which is of great significance for energy storage systems.

High-rate asymmetrical supercapacitors based on cobalt-doped birnessite nanotubes and Mn-FeOOH nanotubes

Co-Doped MnO2 nanotubes (Co-MnO2-5) were prepared as the positive electrode of supercapacitors via a simple one-step hydrothermal method. Co doping and one-dimensional tunneling of nanotubes result in low internal resistance and good ionic contact, enhancing the conductivity and electrochemical performance of the electrodes.

Metal–organic-framework-derived hierarchical Co/CoP-decorated nanoporous carbon polyhedra for robust high-energy storage hybrid supercapacitors

Electrode materials exhibiting nanostructural design, high surface area, tunable pore size, and efficient ion diffusion/transportation are essential for achieving improved electrochemical performance.

Synthesis of FeP nanotube arrays as negative electrode for solid-state asymmetric supercapacitor

Recently, metal phosphides have attracted considerable attention as promising electrode materials for supercapacitors. In this work, FeP nanotube arrays have been successfully synthesized on carbon cloth using ZnO nanorod arrays as the sacrificial templets, via a phosphidation process. The dimensions of the FeP nanotubes are characterized using SEM and TEM showing the diameter to be approximately 200 nm and with a wall thickness of 50-100 nm. The tubular structure of FeP nanotubes provides a facile ion pathway and reduced inner inactive material, thus they are favorable for supercapacitor applications. As a result, the as-synthesized FeP nanotube arrays deliver an improved specific capacitance of 149.11 F g^-1 and a high areal capacitance of 300.1 mF cm^-2 at a current density of 1 mA cm^-2. Furthermore, an MnO₂//FeP solid-state asymmetric supercapacitor was fabricated with a high areal capacitance of 142 mF cm^-2, which indicates the great potential of FeP nanotube arrays to be a high-performing negative electrode material for supercapacitors.