Performance Supercapacitors Research Articles

Synthesis of Eco-friendly Zn-Ni bimetallic MOFs with biodegradable glycolic acid ligands for enhanced supercapacitor performance and hydrogen evolution reaction

Electrochemical technologies like supercapacitors and water-splitting electrolysis are gaining traction due to their impressive efficiency in both energy storage and generation. A hydrothermal technique was employed to synthesize a metal–organic framework (MOF) containing zinc and nickel. Glycolic acid (GA), a naturally occurring biodegradable ligand, was utilized to explore its potential for incorporation into the MOF heterostructure. The ZnNi-MOF (GA) composites showed a notable specific capacity of 1648 C g−1 (2060 F/g) under a current density of 1.0 A g−1 at 70 °C. The study investigated a supercapacitor system design where a combination of polyaniline-doped activated carbon was used for the negative electrode and a zinc-nickel metal–organic framework (GA) was used for the positive electrode. The synthesized ZnNi-MOF (GA)//AC energy storage device demonstrated a specific capacity of 110 C g−1 (55 F g−1) at a higher current density of 2.0 A g−1. The recyclability and stability of device (ZnNi-MOF (GA)//AC) were evaluated using 10000 charge–discharge cycles, yielding an 86% capacity retention. The ZnNi-MOF (GA) composite displayed outstanding catalytic ability in the hydrogen evolution reaction (HER) in comparison to other tested materials, achieving the lowest Tafel slope of 42.79 mV/dec. The findings of our research suggest that ZnNi-MOF (GA) exhibits desirable characteristics that make it a promising material for electrodes in the applications of supercapattery and HER.

N/O Co-doped Porous Carbon with Controllable Porosity Synthesized via an All-in-One Step Method for a High-Rate-Performance Supercapacitor.

A green and economical methodology to fabricate carbon-based materials with suitable pore size distributions is needed to achieve rapid electrolyte diffusion and improve the performance of supercapacitors. Here, a method combining in situ templates with self-activation and self-doping is proposed. By variation of the molar ratio of magnesium folate and potassium folate, the pore size distribution was effectively adjusted. The optimal carbon materials (Kx) have a high specific surface area (1021-1676 m2 g-1) and hierarchical pore structure, which significantly promotes its excellent capacitive properties. Notably, K2 shows an excellent mass specific capacitance of 233 F g-1 at 0.1 A g-1. It still retained 113 F g-1 at 55 A g-1. The assembled symmetric supercapacitor exhibited an outstanding cyclic stability. It maintains 100% capacitance after 100 000 cycles at 10 A g-1. The symmetric supercapacitor demonstrated a maximum power density of 99.8 kW kg-1. This study focuses on the preparation of layered pore structures to provide insights into the sustainable design of carbon materials.

Mechanical Processing with Solid-State of Supercapacitor Materials: A Review of High Energy Milling and High Velocity Particle Methods

Supercapacitors have emerged as a crucial energy storage technology, bridging the gap between traditional capacitors and batteries. The performance of supercapacitors is heavily dependent on the properties of the electrode materials used. Mechanical processing methods, particularly High Energy Milling (HEM) and High-Velocity Particle (HVP) methods have shown great promise in enhancing the physical and electrochemical properties of supercapacitor materials. This review explores the fundamental principles, mechanisms, and recent advancements in HEM and HVP techniques for the synthesis and modification of supercapacitor materials. High energy milling, including ballmill and attritor milling, facilitates particle size reduction, increased surface area, and the creation of nanostructures, leading to improved capacitance and energy density. High velocity particle methods, such as cold spraying and thermal spraying, enable the deposition of uniform and dense coatings, enhancing conductivity and stability. The review also discusses the impact of process parameters on material properties, the challenges faced in scaling up these techniques, and the potential future directions for research. By providing a comprehensive overview of these mechanical processing methods, this paper aims to highlight their significance and potential in advancing supercapacitor technology.

Well-dispersed NiFeS2@Cu2S heterojunction nanorods as high energy density electrode for supercapacitors

Transition metal sulfide heterostructures have demonstrated significant potential in enhancing the performance and cycling stability of supercapacitors due to their adjustable electronic structure. In this study, we synthesized an integrated electrode by constructing NiFeS2@Cu2S heterostructure nanorods onto a copper foam (CF) substrate. The heterostructure displays a crucial role in improving the electrochemical properties of the NiFeS2@Cu2S electrode, which exhibits a high specific capacity of 588 mAh g−1 at a current density of 1 A g−1. Moreover, The assembled CF@NiFeS2@Cu2S //CF@AC asymmetric supercapacitor (ASC) delivers an impressive energy density of 68.6 Wh kg−1 at a power density of 800 W kg−1. This work provides a novel strategy to design and construct highly efficient electrode materials for energy storage applications.

Bipolar Supercapacitive Performance of N-Containing Carbon Materials Derived from Covalent Triazine-Based Framework.

The search for new electrode materials for bipolar-supercapacitor performance is the intention of numerous research in the area of functional framework materials. Among various electrode materials, covalent triazine-based frameworks (CTFs) are in the spotlight drawing much attention as potential electrode material for energy storage. Herein, we present the synthesis of nitrogen-functionalized CTFs marked as CTF-Py-600 and CTF-Py-700 with high nitrogen content (18% and 14%, respectively) for supercapacitor application by applying 2,6-dicyanopyridine monomer via the polymerization reaction under ionothermal condition. The BET surface area of these materials are in the range of 940-1999 m2g-1. CTF-Py-700 demonstrates outstanding electrochemical performance in both potential windows. At the negative potential window, it exhibits a higher specific capacitance of 435 F g-1 (at 1 A g-1) compared to the positive potential window, where it shows a specific capacitance of 306 F g-1 (at 1 A g-1) owing to the synergistic existence of its large surface area (1999 m2g-1) and high nitrogen content (14%) with inherent microporosity. Remarkable cycling stability without noticeable degradation of specific capacitance after 15000 cycles was recorded for CTF-Py-700. This suggests that the nitrogen-functionalized CTFs are going to be a highly demanded electrode material for electrochemical energy storage applications.

Oxalate-derived porous C-doped NiO with amorphous-crystalline heterophase for supercapacitors

Constructing amorphous/crystalline heterophase structure with high porosity is a promising strategy to effectively tailor the physicochemical properties of electrode materials and further improve the electrochemical performance of supercapacitors. Here, the porous C-doped NiO (C-NiO) with amorphous/crystalline heterophase grown on NF was prepared using NF as Ni source via a self-sacrificial template method. Calcining the self-sacrificial NiC2O4 template at a suitable temperature (400 °C) was beneficial to the formation of porous heterophase structure with abundant cavities and cracks, resulting in high electrical conductivity and rich ion/electron-transport channels. The density functional theory (DFT) calculations further verified that in-situ C-doping could modulate the electronic structure and enhance the OH− adsorption capability. The unique porous amorphous/crystalline heterophase structure greatly accelerated electrons/ions transfer and Faradaic reaction kinetic, which effectively improved the charge storage. The C-NiO calcined at 400 °C (C-NiO(400)) displayed a markedly enhanced specific charge, outstanding rate property and excellent cycling stability. Furthermore, the hybrid supercapacitor assembled by C-NiO(400) and active carbon achieved a high energy density of 49.0 Wh kg−1 at 800 W kg−1 and excellent cycle stability (90.9 % retention at 5 A/g after 10 000 cycles). This work provided a new strategy for designing amorphous/crystalline heterophase electrode materials in high-performance energy storage.

Preparation of MnS/NiCo2S4 composite nanosheets self-supported electrode and the performance in water-system asymmetric supercapacitors

Abstract In this paper, the MnS@NiCo2S4 composite self-supporting electrode was designed and prepared with a mixture of nickel, cobalt, and manganese sulfide as the research object. The capacitance of the electrode can reach 2, 372.7 F g−1 at the current density of 1 A g−1, and the voltage window can also be widened to 0-0.6 V and maintains a multiplier performance of 62.1% at 10 A g−1. Following 5, 000 cycles of charging and discharging, the electrode exhibits a capacity retention of 78.2% relative to its initial capacity, with the coulombic efficiency consistently hovering around 100%. This performance indicates that the electrode can carry out stable and reversible electrochemical processes. A supercapacitor assembled with 1 M KOH as the electrolyte, activated carbon as the anode, and MnS/NiCo2S4 as the cathode, delivers an energy density of 46.9 W h kg−1. In the life test of the charge and discharge cycle, the discharge capacity after 10, 000 cycles is 89.2% of the initial capacity, indicating that the device has good cycle stability. This study provides an idea for the potential application of metal sulfide-based electrodes with wide potential windows and high electrochemical properties in water asymmetric supercapacitors.

Supercapacitors and rechargeable batteries, a tale of two technologies: Past, present and beyond

Supercapacitors and rechargeable batteries are energy storage devices where the performance strengths of one are traditionally the weaknesses of the other. Batteries benefit from superior energy storage capacity while supercapacitors possess higher power rates and longer cycle life. The rapid adoption of these devices in electric vehicles and grid energy storage applications is driving their further development and production. Accumulating and comprehending the current knowledge of both device technologies shall serve as a foundation for the progress in future research and development within these two distinct fields that share common goals. Therefore, in this review, we aggregate the supercapacitor and battery energy-power performance trends from over the last 18 years, to construct a projection of where the technologies could be heading in the coming decade. We specifically discuss the influence of each of these technologies in the energy storage landscape and their effect on hybridization research. Projections of the trends suggest that by 2040 the best-performing asymmetric and hybrid supercapacitors could be comparable to commercial battery technologies that are currently under development, in terms of energy density (ED). In terms of power density (PD), battery technology can achieve performance comparable to certain electrical double layer (EDL)-based supercapacitors. For some applications, we foresee that the two devices will continue to hybridize to fill the energy-power gap in a way that the penalty to PD for enhanced ED becomes insignificant. This expected improvement may eventually reach a saturation point, suggesting that once a certain level of ED is achieved, any further enhancements of the metric only lead to severe trade-offs with PD, and vice versa. The saturation observed in these technologies has also prompted an exploration of new pathways, with a notable emphasis on sustainability, to achieve high performance using renewable materials and methods.

Wide electrochemical stability window of NaClO4 water-in-salt electrolyte elevates the supercapacitive performance of poly(3,4-ethylenedioxythiophene)

Water-in-salt electrolytes (WiSEs) have emerged as the primary preference in the domain of aqueous-based supercapacitors, thanks to their wide electrochemical stability window (ESW > 1.23 V). Here, we have chemically synthesized a unique lettuce coral-like structure of tosylate doped-poly(3,4-ethylenedioxythiophene) (PEDOT-tos) and tested it for supercapacitor application in a 17 molal (m) NaClO4 WiSE, achieving an ESW of 1.9 V. The energy and power densities (Ed and Pd) of our PEDOT-tos supercapacitor are as high as 14 Wh kg-1 and 7210 W kg-1, respectively, with over 80 % capacitance retention after 10,000 continuous Galvanostatic charge-discharge cycles. The NaClO4 WiSE increases the Ed and Pd of PEDOT by several folds compared to traditional H2SO4 electrolyte. This work encourages the exploration of a suitable combination of a PEDOT-based composite material and WiSE for high-performance supercapacitors.

Unlocking Enhanced Electrochemical Performance of MBene-MoB Through Controlled Aluminum Dissipation from MoAlB.

2D transition metal borides, known as MBenes, have attracted considerable attention due to their exceptional properties. This study explores the feasibility of aluminum (Al) etching from MoAlB using environmentally friendly and sustainable fluoride-free dilute acidic/alkaline solutions at room temperature, revealing its thermodynamic and kinetic viability. Furthermore, it is found that complete removal of Al can be achieved in dilute alkaline reagent under hydrothermal conditions, yielding pristine single/few-layered MBene-MoB for the first time, while acidic solutions result in ≈33% etching rates. XRD refinement, which tracks aluminum removal from 0% to 100%, reveals transient metastable phases of MoAl1-xB (x<0.5) in the initial etching stages, evolving into relatively stable pure Mo2AlB2 structures with 50% Al deficiency, serving as a precursor to MBenes. The subsequent loss of Al results in a 2D MBene-MoB structure. DFT calculations confirm excellent conductivity for MoAlB, MoAl1-xB (x=0-1), and MBene-MoB. Remarkably, MBene-MoB exhibits superior supercapacitor performance with a 4025.60mFcm-2/201.28Fg-1 capacitance. Simulations validate rapid electrolyte diffusion in layered MBene-MoB, contributing significantly to enhanced capacitance. Additionally, in the hydrogen evolution reaction (HER), MBene-MoB demonstrates superior catalytic activity compared to the precursor MoAlB and commercial MoB. Calculations suggest the potential for enhancing HER through surface modulation, considering its suboptimal hydrogen adsorption energy.

Environmental and Energy Applications of Graphene-Based Nanocomposites: A Brief Review

Chemically stable two-dimensional nanostructured graphene with huge surface area, high electrical conductivity and mechanical excellence has gained significant research attention in the past two decades. Its excellent characteristics make graphene one of the important materials in various applications such as environmental and energy storage devices. Graphene no doubt has been a top priority among the carbon nanomaterials owing to its structure and properties. However, the functionalization of graphene leads to various nanocomposites where its properties are tailored to be suited for various applications with more performance, environmental friendliness, efficiency, durability and cost effectiveness. Graphene nanocomposites are said to exhibit more surface area, conductivity, power conversion efficiency and other characteristics in energy devices like supercapacitors. This review was aimed to present some of the applications of graphene-based nanocomposites in energy conversion devices like supercapacitors and Li-ion batteries and some of the environmental applications. It was observed that the performance of supercapacitors was obstructed due to restacking and agglomeration of graphene layers. This was addressed by combining MO (metal oxide) or CP (conducting polymer) with graphene as material for electrodes. Electrodes with CP or MO/graphene composites are summarized. Heterogeneous catalysts were of environmental concern in recent years. In this context, graphene-based nanocomposites gained significance due to expansion in structural diversity. A minimum overview is presented in this paper in terms of structural aspects and properties of GO/rGO-based materials used in supercapacitors and environmental applications like dye removal. Continuous efforts towards synthesis of productive graphene-based nanocomposites might lead to significant output in applications related to environment and energy sectors.

Mangosteen husk-derived porous carbon for quasi solid-state supercapacitor with advanced performances

Exploiting advanced electrode materials and electrolytes are two fundamental approaches to enhance the electrochemical performances of supercapacitor. Herein, mangosteen husk-derived porous carbon (MHPC) and KOH gel-electrolyte are prepared and applied in quasi solid-state supercapacitor. In coin-type supercapacitor employing 6 M KOH gel-electrolyte, the MHPC electrode exhibits a high specific capacitance of 285 F g−1 at a current density of 0.2 A g−1, coupled with exceptional cyclability, retaining 88.9 % of its initial capacity after 10,000 cycles. Additionally, the elaborated MHPC electrode and 6 M KOH gel-electrolyte enabled the flexible device in maintaining superior capacitive properties under arbitrary bending angles. Our findings present an avenue in the development of cost-effective and highly safe energy storage devices.

Machine learning prediction of supercapacitor performance of N-doped biochar from biomass wastes based on N-containing groups, element compositions, and pore structures

N-doped biochar has great potential for development in the field of supercapacitors. In this study, Random Forest and Extreme Gradient Boosting models are used to predict the specific capacitance of N-doped biochar. The prediction is based on several features, including pore structure parameters, element composition, N-containing group of N-doped biochar, and electrochemical testing characteristics. Shapley additive explanations and partial dependency plots are used to explore the impact of the features on specific capacitance. Results show that both the Random Forest and the Extreme Gradient Boosting models exhibited excellent prediction performance, with R2 of 0.95 and 0.96, respectively. N-6 contributes more to the higher specific capacitance among the three N-containing groups. According to the partial dependency plots, when the specific surface area, pore size, and degree of graphitization are around 2200 m2/g, 4 nm, and 1, respectively, the specific capacitance of N-doped biochar is about 303 F/g at 1 A/g. In addition, a procedure for predicting the specific capacitance of N-doped biochar is developed based on the PySimpleGUI library and the Extreme Gradient Boosting model. This study provides a reference for the preparation of high specific capacitance of N-doped biochar.

Exploring the electrochemical and electrocatalytic performance of bismuth oxide and bismuth manganese oxide nanostructures for supercapacitor and water splitting

In this research, bismuth oxide (BO) with non-uniform nanorods featuring a monoclinic crystal structure and bismuth manganese oxide (BMO) with irregularly shaped nanosheets exhibiting a cubic crystal structure were synthesized hydrothermally. These materials were designed for applications in supercapacitors and the oxygen evolution reaction (OER). Electrochemical analysis of BO-NF (Nickel Foam) and BMO-NF electrodes in KOH highlights BMO's superior performance for both supercapacitor and water splitting applications. BMO-NF electrode exhibit higher specific capacitance, lower resistance, and exceptional cyclic stability compared to BO-NF electrode. In asymmetric liquid-state supercapacitor devices, BMO-NF electrode outperforms BO-NF electrode, showcasing advanced capabilities. Additionally, for water splitting, BMO-NF electrode demonstrates a lower overpotential, a more favourable Tafel slope, a larger electrochemical active surface area, and greater stability, underscoring its enhanced efficiency and reliability. Overall, this study shows that the BMO is found to be the more promising material for the energy storage and electrocatalytic applications.

Current insights and future prospects of graphene aerogel-enhanced supercapacitors: A systematic review

Supercapacitors present a compelling alternative to conventional batteries, offering rapid energy storage and high power density. Despite their advantages, they typically fall short in energy density compared to traditional batteries, primarily due to limitations in electrode materials. Graphene Aerogels (GA) have emerged as a promising solution to enhance supercapacitor performance because of their unique properties, such as high surface area and excellent conductivity. This systematic review provides a comprehensive analysis of recent advancements in GA technology, focusing on their synthesis methods and applications in supercapacitors. It highlights significant improvements that GA can bring to Electric Double-Layer Capacitors (EDLCs), pseudocapacitors, and hybrid supercapacitors. Additionally, the review explores GA's potential for enhancing electric generators and integrating into flexible, wearable technologies. Future research directions are emphasised, particularly regarding GA’s potential applications in waste management and environmental protection. The review was conducted through a thorough literature search, prioritising peer-reviewed sources related to GA synthesis and supercapacitor applications. Methodological quality and potential biases of the included studies were assessed using principles similar to the Cochrane Risk of Bias tool. Thematic analysis was employed to synthesise findings and identify key trends and challenges. Limitations such as potential biases and methodological variations are discussed. Overall, this review highlights the technological prospects of GA and provides guidance for future research in supercapacitor development and applications.

Improving energy density of battery-type electrode material by growing β-Ni(OH)2 in situ on biochar for hybrid supercapacitors

The insufficient energy density of electrode materials has hindered the popularity and application of supercapacitors. The construction of hybrid supercapacitors offers an ideal solution by combining transition-metal hydroxides with high specific capacity and biochar with excellent conductivity. In this study, an electrode material (β-Ni(OH)2@AC22 composite) was created by in situ growth flower-like β-Ni(OH)2 nanosheets on biochar (AC) that extracted from the seed coat of Xanthoceras sorbifolium Bunge. This β-Ni(OH)2@AC22 composite exhibited a remarkable specific capacity of 617.5C g−1 (1 A g−1), nearly four times that of AC, and remarkable cycling stability (85.6 % retention after 5000 cycles). Using this composite as the positive electrode and biochar as the negative electrode, the assembled battery-type hybrid supercapacitors (HSCs) achieved a specific capacity of 92.75C g−1 (1 A g−1). The HSCs demonstrated a specific energy of 57.9 Wh kg−1, a specific power of 750.9 W kg−1, and even maintained 42.2 Wh kg−1 at a maximum specific power of 6049.4 W kg−1. The device maintained a specific capacity of about 78.7 % after 7000 charging/discharging cycles, demonstrating good practical performance. These results highlight the practical application potential of the prepared composites in supercapacitors, with biochar serving as a basis for enhancing the electrochemical performance of supercapacitors.

Incorporating Ag into Nd-Succinate MOF: Tunned electrochemical supercapacitor behaviour of Ag modified Nd-Succinate and electrochemical reaction mechanism

The electrode materials must be tailored to achieve higher energy and power densities and thus improve the supercapacitor's performance. This study explores the impact of incorporating Silver (Ag) into a Neodymium-Succinate Metal Organic Framework (Nd-Succinate) on supercapacitor behaviour. Initially, the Nd-Succinate MOF was characterized by structural, morphological, and spectroscopic characterizations. Subsequently, Ag/Nd-Succinate was synthesized and characterized. The electrochemical performance of Ag/Nd-Succinate was evaluated in a 6 M KOH electrolyte; the results indicated a significant enhancement in supercapacitor performance upon incorporating Ag into parent Nd-Succinate. From galvanostatic Charge-Discharge cycles (GCD), the capacitance for Ag/Nd-Succinate was determined to be 1389 F/g, i.e., 42 % higher than that of bare Nd-Succinate which was measured at 978 F/g. at a current density of 1.25 A/g. Ag/Nd-Succinate showcased an 89 % retention value for multiple retention cycles, slightly higher than the retention value obtained (84 %) for Nd-Succinate. The results of electrochemical experiments (Cyclic voltammetry (CV) and Electrochemical Impedance Spectra (EIS)) provided information about the nature of electron transfer and capacitance enhancement upon the introduction of Ag into Nd-Succinate. These findings provide valuable information on modifying MOFs and introducing metal that will help produce high-performance supercapacitor electrodes.

Probing the layer-dependent behavior of electronic properties and quantum capacitance in 2H MoS2: A computational analysis with emphasis on mechanical stability

The quest for clean, sustainable energy sources was prompted by the fast depletion of fossil fuels and the world's expanding energy requirements. To store renewable energy, it is important that effective energy storage devices such as supercapacitor (SCs) be manufactured. SCs offer a promising avenue for fast-charging, energy storage, and long-life cycles but maximizing their energy density remains a problem. This study theoretically explores the intrinsic Quantum capacitance (Cq) of MoS2 in the 2H phase with a few number of layers and how factors like electronic structure and density of states influence its capacitance behavior. In the present work, the first principles analysis utilizing computational modelling with Density Functional Theory (DFT) has been employed to investigate the Cq and surface charge density (σ) of MoS2. By explaining the connection between MoS2's electrical and structural properties with its Cq, valuable insights for optimizing it's SC performance were obtained. Both the density of states (DOS) and the Cq increase with the number of layers. Among the observed structures the highest value of Cq is observed for the three layered structure of 2H–MoS2 (2H3L-MoS2) at +1 V which is 1615.14 μF cm−2. Investigating the mechanical stability of optimized structure (2H3L-MoS2), a high Young's modulus of 180.46 GPa is observed for 2H3L structure. Hence, 2H-phase of MoS2 can be used as an excellent anode material for asymmetric SCs and flexible electronic devices.

Construction of ultra-thin NiMo3S4 nanosheet sphere electrode for high-performance hybrid supercapacitor

The construction of electrode materials with rational morphology and structure based on bimetallic sulfides is crucial to improve the performance of supercapacitors. Ultra-thin three-dimensional nickel molybdenum sulfide nanosheet spheres (NiMo3S4 NSSs) are grown on nickel foam (NF) using a one-step hydrothermal synthesis. NiMo3S4 NSSs have a diameter of ∼ 5 μm and nanosheet thickness of 200 nm. The effects of increasing the hydrothermal synthesis time and molar concentration ratios of Ni2+ to MoO42- on the morphologies of the NiMo3S4 are investigated. Due to the synergistic effect of NiMo3S4 NSSs and bimetallic ions which can provide a larger solution contact areas and improve the redox activity, the electrode exhibits good electrochemical properties. The specific capacity of NiMo3S4 NSSs/NF electrode can reach 1002.4 C/g (1 A/g). After being assembled into a hybrid supercapacitor (HSC) with activated carbon (AC), the energy density can reach 72.1 Wh/kg at the power density of 749.9 W/kg. In addition, the HSC shows an excellent stability of 89 % after 10, 000 charge-discharge cycles (10 A/g).

Improved supercapacitive performance based on novel RuO2/SiO2 nanocomposites

In this work, RuO2/SiO2 nanocomposites are synthesized by dispersing RuO2 in SiO2 nanoparticles with hydrothermal method. The morphology and structure of the composites are comprehensively characterized and confirmed that the agglomeration of RuO2 is reduced and their dispersion is enhanced. Their supercapacitive performances are evaluated by electrochemical tests. It shows that the RuO2/SiO2 nanocomposite provides a specific capacitance of 1785.1 F g−1 at 1 A g−1 and maintains 90.7 % capacitance retention after 10,000 cycles. Asymmetric supercapacitors are prepared with the RuO2/SiO2 composite as the positive electrode and conductive carbon as the negative electrode. The specific capacitance is 159.4 F g−1 at 0.05 A g−1. An energy density of 14.2 Wh kg−1 is obtained at a power density of 79.9 W kg−1. Through the doping of SiO2, RuO2 grows dispersedly outside SiO2, and thus the agglomeration of RuO2 is weakened, and both proton diffusion and electron transfer are effectively enhanced, and the electrochemical properties are improved significantly, showing great potential for commercial applications.