Photo-powered energy storage devices are attracting significant research interest due to their potential application in smart electronics. They have become a promising alternative to current energy sources and are suitable as next-generation power sources. Both planar and flexible/fiber photosupercapacitors are in the limelight due to their ease of fabrication, economic compatibility and multi-axial flexibility. A large number of integrated devices have emerged in the last decade, and among them, solar cell devices combined with supercapacitors have unique photo conversion and storage properties with promising overall efficiency. Thus, researchers have tried a wide variety of device combinations, and all reports are well sorted in this review. Herein, we comprehensively discuss different types of photo-powered supercapacitors with their design configuration, working mechanism and fabrication. Finally, the future direction, opportunities and challenges in this research field are discussed.

Photo-powered integrated supercapacitors: a review on recent developments, challenges and future perspectives

Deciphering of the charge storage mechanism of conventional supercapacitors (SCs) can be a humongous stride towards developing high energy density and prolonged cyclability based SCs which can cease the energy crisis to a greater extent. Though ex-situ characterization techniques have helped to puzzle out the charge storage mechanism of the SCs, voluminous untrodden grey areas with unknown ensembles are still out there which cannot be left behind. Lately, in situ analytical characterization tools such as in situ X-ray diffraction (XRD), in situ X-ray absorption spectroscopy (XAS), in situ X-ray photoelectron spectroscopy (XPS), in situ Raman, in situ infrared/Fourier-transform infrared spectroscopy (IR/FTIR), in situ nuclear magnetic resonance (NMR), in situ atomic force microscopy (AFM), in situ scanning electron microscopy (SEM), in situ tunnelling electron microscopy (TEM), in situ electrochemical quartz crystal microbalance (EQCM) techniques etc. have exclusively come into picture to throw some light on the charge storage mechanism of SCs over the past decade or so. This review solely emphases on the insights of the charge storage mechanism interpreted from in situ characterization techniques along with the theoretical investigation validations. Various charge storage parameters obtained from electronic structure simulations like quantum capacitance, voltage induced by electrolyte ions, diffusion energy barrier of electrolyte ions etc. have been particularized with pertinent examples. Both the amalgamation of in situ techniques as well as theoretical simulations can efficiently elucidate the ion dynamics and charge transfer of the SC electrode systems with a whole new perspective. However, the comprehensive classification of SCs based on mechanism, choice of electrodes and device configuration, enlightenment of charge storage mechanism by in situ/operando techniques along with theoretical explorations can be retrieved in this audit.

Understanding the charge storage mechanism of supercapacitors: in situ/operando spectroscopic approaches and theoretical investigations

The world is currently facing critical water and energy issues due to the growing population and industrialization, calling for methods to obtain potable water, e.g., by photocatalysis, and to convert solar energy into fuels such as chemical or electrical energy, then storing this energy. Energy storage has been recently improved by using electrochemical capacitors and ion batteries. Research is actually focusing on the synthesis of materials and hybrids displaying improved electronic, physiochemical, electrical, and optical properties. Here, we review molybdenum disulfide (MoS2) materials and hybrids with focus on synthesis, electronic structure and properties, calculations of state, bandgap and charge density profiles, and applications in energy storage and water remediation.

/pdf/mos2-based-nanocomposites-synthesis-structure-and-4nxxxffvng.pdf

MoS2-based nanocomposites: synthesis, structure, and applications in water remediation and energy storage: a review

2D@3D MoS2@Ni/Co-S submicroboxes derived from prussian blue analouges for high performance supercapacitors

Flexible supercapacitors assembled with two-dimensional materials have become a research hotspot in recent years. Here, we have prepared two-dimensional nanomaterial MoS2 and SWCNT, CNF aerogel composite electrode, and its flexible all-solid-state supercapacitor. SWCNT can inhibit the accumulation of MoS2 nanosheets and enhance the conductivity of the composite electrode. CNF can improve the dispersion uniformity of MoS2 and SWCNT, and endow the composite electrode with a high specific surface area (328.86 m2 g–1) and excellent flexibility. MoS2–SWCNT/CNF supercapacitor has a good rectangular CV curve and symmetrical triangular GCD curve. The CV curve of the MoSCF3 supercapacitor with the highest MoS2–SWCNT content remains rectangular even at the scanning rate of 2000 mV s–1. Its voltage window can reach 1.5 V. MoS2–SWCNT/CNF supercapacitor has a specific capacity of 605.32 mF cm–2 (scanning rate of 2 mV s–1) and 30.34 F g–1 (0.01 A g–1), an area specific energy of 35.61 mWh cm–2 (area specific power of 0.03 mW cm–2), and extremely high cycle stability (91.01% specific capacity retention rate after 10 000 cycles) and good flexibility. The fine nanocomposite structure gives MoS2–SWCNT/CNF supercapacitor impressive electrochemical performance and excellent flexibility, which can be used in the field of portable electronic devices and flexible devices.

https://pubs.acs.org/doi/pdf/10.1021/acsomega.2c01815

Flexible and Freestanding MoS2 Nanosheet/Carbon Nanotube/Cellulose Nanofibril Hybrid Aerogel Film for High-Performance All-Solid-State Supercapacitors

Excellent cyclic stability and fast charge/discharge capacity demonstrated by supercapacitors foster research interest into new electrode materials with 100% cycle life and high specific capacitance. We report an improvement in the electrochemical performance of MoS2/multiwalled carbon nanotubes (MWCNT) nanohybrid and intensively explored its performance in symmetric and asymmetric supercapacitor (ASC) assembly. The symmetric assembly of MoS2/MWCNT exhibits capacitance of around 274.63 F g-1 at 2 A g-1 with higher specific energy/power outputs (20.70 Wh kg-1/1.49 kW kg-1) as compared to the supercapacitor based on pristine MoS2 (5.82 Wh kg-1/1.07 kW kg-1). On the other hand, a unique all-carbon-based ASC assembled with MoS2/MWCNT and VSe2/MWCNT composite with K2SO4 as electrolyte delivers the highest energy density of 32.18 Wh kg-1 at a power density of 1.121 kW kg-1 with exceptional cycling stability and excellent retention of about 98.43% even after 5000 cycles. These outstanding results demonstrate the excellent electrochemical properties of both symmetric and asymmetric systems with high energy density and performance, which further enable them to be a potential candidate for supercapacitor applications.

https://iopscience.iop.org/article/10.1088/1361-6528/abd05b/pdf

Energy storage performance of 2D MoS2 and carbon nanotube heterojunctions in symmetric and asymmetric configuration.

Vanadium Diselenide (VSe2) is a prominent candidate in the 2D transition metal dichalcogenides family for energy storage applications. Herein, we report the experimental and theoretical investigations on the effect of cobalt doping in 1T-VSe2. The energy storage performance in terms of specific capacitance, stability and energy and power density is studied. It is observed that 3% Co doped VSe2 exhibits better energy storage performance as compared to other concentrations, with a specific capacitance of ∼193 F g−1 in a two-electrode symmetric configuration. First-principles Density Functional Theory based simulations support the experimental findings by suggesting an enhanced quantum capacitance value after the Co doping in the 1T-VSe2. By making use of the advantages of the specific electrode materials, a solid state asymmetric supercapacitor (SASC) is also assembled with MoS2 as the negative electrode. The assembled Co-VSe2//MoS2 SASC device shows excellent energy storage performance with a maximum energy density of 33.36 Wh kg−1 and a maximum power density of 5148 W kg−1 with a cyclic stability of 90% after 5000 galvano static charge discharge cycles.

Sree Raj K A

Papers

Energy storage performance of 2D MoS2 and carbon nanotube heterojunctions in symmetric and asymmetric configuration.

Effect of cobalt doping on the enhanced energy storage performance of 2D vanadium diselenide: experimental and theoretical investigations