A high-temperature phosphorization for synthesis of core-shell Ni-NixPy@C nanocomposite-immobilized sponge-like P-doped porous carbon with excellent supercapacitance performance

Ni12P5 and Ni12P5-rGO for multifunctional electrocatalyst and supercapacitor application

Transition metal phosphides are crucial for various environmental and energy applications. In this study, porous Ni12P5 and Ni12P5-rGO were synthesized using a one-step solvothermal method. Red phosphorus served as the phosphorus source, while ethylene glycol acted as a capping agent to promote the formation of nanomaterials within a nitrogen-rich atmosphere. The catalytic performance of these materials was evaluated through their hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and capacitance properties. Notably, Ni12P5-rGO exhibited Tafel slopes of 66 mV/dec for OER and 33 mV/dec for HER, indicating enhanced charge transfer efficiency compared to Ni12P5, which showed slopes of 78 mV/dec and 102 mV/dec, respectively. This improvement suggests that Ni12P5-rGO facilitates faster electron transfer, resulting in superior catalytic performance. Additionally, the synergistic effect of reduced graphene oxide (rGO) contributes to improved charge storage capabilities. The Ni12P5-rGO demonstrated a specific capacitance of 192 F/g, significantly higher than the 110 F/g observed for Ni12P5 at a current density of 1 A/g. Remarkably, these materials maintained their capacity over 5000 cycles, achieving a commendable 98 % coulombic efficiency. These findings highlight the potential of Ni12P5-rGO as an effective material for energy conversion and storage applications, showcasing its promising role in advancing the efficiency of related technologies.

Porous prussian blue analogs derived nickel-iron bimetallic phosphide nanocubes on conductive hollow mesoporous carbon nanospheres for stable and flexible high-performance supercapacitor electrode

Nickel-iron bimetallic phosphide (Ni-Fe-P) is the ideal battery-type materials for supercapacitor in virtue of high theoretical specific capacitance. Nevertheless, its actual adhibition is astricted on account of inferior rate capability and cyclic stability. Herein, we constructed hierarchical core-shell nanocomposites with hollow mesoporous carbon nanospheres (HMCS) packaged via prussian blue analogs derived Ni-Fe-P nanocubes (Ni-Fe-P@HMCS), as a positive electrode for hybrid supercapacitor (HSC). Profiting from the cooperative effects of Ni-Fe-P nanocubes with small size and good dispersibility, and HMCS with continuously conductive network, the Ni-Fe-P@HMCS composite electrode with abundantly porous architectures presents an ultrahigh gravimetric specific capacity for 739.8 C g-1 under 1 A g-1. Specially, the Ni-Fe-P@HMCS electrode presents outstanding rate capability of 78.4% (1 A g-1 to 20 A g-1) and cyclic constancy for 105% after 5000 cycles. Density functional theory implies that the composite electrode possesses higher electrical conductivity than bare Ni-Fe-P electrode by reason of the incremental charge density, and the electrons transferring from NiFe3P4 to HMCS layers. Additionally, the assembled Ni-Fe-P@HMCS//HMCS HSC facility delivers the high energy density for 64.1 Wh kg-1, remarkable flexibility and mechanical stability. Thus, this work proffers a viable and efficacious measure to construct ultra-stability electrode for high-performance portable electronic facilities.

Hollow nanotube arrays of nickle-cobalt metal sulfide for high energy density supercapacitors

High energy density is still difficult to achieve using existing metal sulfides because of their low specific capacitance. To improve capacitance, a series of nickel and cobalt metal sulfides with different Ni/Co ratios were synthesized by a two-step hydrothermal method. Using the combining method of experimental research and first-principles calculation, the morphology, structural stability, electronic structure and electrochemical properties of metal sulfides were investigated systematically. The results show that the morphology of metal sulfides gradually grows from two-dimensional structure to nanotube arrays, and finally to nanorod arrays, as the Ni/Co ratios decrease. Among them, the NC24 sample with the Ni/Co ratio of 1 : 2 is a hollow nanotube array composed of NiCo₂S₄, which shows excellent electrochemical performance. The specific capacity of the NC24 sample reaches 1527C g^-1 at 1 A g^-1, and the capacity retention is 93.81% at 10 A g^-1 after 2000 cycles. Furthermore, a symmetrical supercapacitor assembled from the NiCo₂S₄ nanotube array shows a high energy density of 67.5 W h kg^-1. This strategy develops a nanotube array of metal sulfides and expands its application in a high energy density supercapacitor.

Status review of nickel phosphides for hybrid supercapacitors

Transition metal phosphides are a new class of materials that have attracted enormous attention as a potential electrode for supercapacitors (SCs) compared to metal oxides/hydroxides and metal sulfides due to their strong redox-active behaviour, good electrical conductivity, layered structure, low cost, and high chemical and thermal stability. Recently, several efforts have been made to develop nickel phosphides (Ni_xP_y) (NPs) for high-performance SCs. The electrochemical properties of NPs can be easily tuned by several innovative approaches, such as heteroatom doping, defect engineering, and developing a hollow architecture. The prospects of NPs as a positive electrode in hybrid SCs are summarized to understand the material's practical relevance. Finally, the challenges and perspectives are provided for the development of high-performance NPs for SCs. The thorough elucidation of the structure-property-performance relationship offers a guide for developing NP-based next-generation energy-storage devices.

B,N-Codoped Porous C with Controllable N Species as an Electrode Material for Supercapacitors

Manufacturing heteroatom-doped porous C with controllable N species is an important issue for supercapacitors. Herein, we report a low-cost and simplified strategy for synthesizing B,N-codoped porous C (BNPC) by a freeze-drying chitosan-boric acid aerogel beads and subsequent carbonization treatment. The BNPC samples were studied using various characterization technologies. The introduction of boric acid to chitosan successfully induced the formation of B,N-codoped C with a well-developed 3D interconnected porous structure. The B doping had a significant impact on the distribution of N species in the samples. Moreover, the good wettability of the sample resulting from B doping is favorable for electrolyte diffusion and ion transport. As a consequence, the optimal BNPC sample showed an excellent specific capacitance of 240 F g^-1 at 0.5 A g^-1 and an outstanding capacitance retention of 95.1% after 10000 cycles at 5 A g^-1. An assembled symmetrical supercapacitor displayed an energy density of 11.4 Wh kg^-1 at a power density of 250 W kg^-1. The proposed work provides a simple and effective method to obtain B,N-codoped C-based materials with high electrochemical performance.

One-pot construction of highly oriented Co-MOF nanoneedle arrays on Co foam for high-performance supercapacitor

Highly oriented Co-MOF nanoneedle arrays arein situconstructed on Co foam (Co-MOF@Co) by using a one-pot solvothermal strategy. As-prepared Co-MOF@Co can be directly served as a binder-free electrode for supercapacitor, which exhibits wonderful electrochemical performances, i.e. high specific capacitance (12783.0 mF cm^-2or 1164.2 F g^-1), exceptional cycling stability (90.5% retention over 10 000 cycles at 250 mA cm^-2) with a loading of 10.98 mg cm^-2. Meanwhile, an asymmetric supercapacitor of AC//Co-MOF@Co delivers a high ratability (87% retention upon ten-fold current density) and high energy density of 43.4 W h kg^-1at the power density of 145.1 W kg^-1.