The investigation of inexpensive, effective, environmentally friendly next-generation energy storage devices is an urgent task due to the discontinuities of new generation energy that hinder their further widely application. Among the multitudinous explored energy storage devices, supercapacitors have been regarded as the most potential energy storage systems thanks to their distinctive features of ultralong cycling lifespan, ultrafast charge/discharge process, and high power density compared with batteries and conventional capacitors. Nevertheless, the existing defect of low energy density has always been a bottleneck problem to their long-term development and widespread applications. Meanwhile, the electrodes are the core component in supercapacitors, determining the electrochemical performance directly. Consequently, transition metal oxides were chosen as the promoting materials to design and fabricate appropriately and rationally act as supercapacitor electrodes to harvest the outstanding electrochemical performance of both high energy and power density simultaneously. Here, we summarized the recent advances in transition metal oxides with different dimensions as electrodes for high-performance supercapacitors, including zero-dimensional nanostructures (nanospheres, nanocrystals, nanoparticles), one-dimensional nanostructures (nanorods, nanowires and nanotubes), two-dimensional nanostructures (nanoflakes, nanoplatelets), three-dimensional nanostructures (spherical structure, hollow structure, flower-like structure, honeycomb structure, mesoporous structure), and the corresponding supercapacitors electrochemical performance, expecting to make a thorough inquiry of the relationship between structure and property for highlighting the route to design and synthesis high-performance transition metal oxide-based supercapacitor electrodes.

Recent advances in transition metal oxides with different dimensions as electrodes for high-performance supercapacitors

Molybdenum disulfide (MoS2) is a promising nonprecious catalyst for the hydrogen evolution reaction (HER) that has been extensively studied due to its excellent performance, but the lack of understanding of the factors that impact its catalytic activity hinders further design and enhancement of MoS2-based electrocatalysts. Here, by using novel porous (holey) metallic 1T phase MoS2 nanosheets synthesized by a liquid-ammonia-assisted lithiation route, we systematically investigated the contributions of crystal structure (phase), edges, and sulfur vacancies (S-vacancies) to the catalytic activity toward HER from five representative MoS2 nanosheet samples, including 2H and 1T phase, porous 2H and 1T phase, and sulfur-compensated porous 2H phase. Superior HER catalytic activity was achieved in the porous 1T phase MoS2 nanosheets that have even more edges and S-vacancies than conventional 1T phase MoS2. A comparative study revealed that the phase serves as the key role in determining the HER performance, as 1T phase MoS2 always outperforms the corresponding 2H phase MoS2 samples, and that both edges and S-vacancies also contribute significantly to the catalytic activity in porous MoS2 samples. Then, using combined defect characterization techniques of electron spin resonance spectroscopy and positron annihilation lifetime spectroscopy to quantify the S-vacancies, the contributions of each factor were individually elucidated. This study presents new insights and opens up new avenues for designing electrocatalysts based on MoS2 or other layered materials with enhanced HER performance.

(Invited) Contributions of Phase, Sulfur Vacancies, and Edges to the Hydrogen Evolution Reaction Catalytic Activity of Porous Molybdenum Disulfide Nanosheets

Metal-organic framework-derived nanocomposites for electrocatalytic hydrogen evolution reaction

Beyond conventional hybrid ion capacitors (HICs) based on porous carbon capacitive materials, the introduction of faradaic pseudocapacitance in HICs is an effective method to enhance energy density. Herein, we prepare methylene blue functionalized graphene (MB-X) composites taking advantage of electrostatic and extensive π-conjugated interaction. The test results confirm that the composites have high rate capability and excellent cycle stability on account of the synergistic effect between graphene and MB molecules. In order to improve the safety of HICs, an aqueous electrolyte is a promising candidate as long as the cell voltage can be efficiently increased. Therefore, we skillfully employ aqueous solutions with different pH values as asymmetric electrolytes to assemble HICs, where polyimide acts as the battery material and MB-X serves as the capacitive material. Thanks to the asymmetric electrolytes, the constructed aqueous HICs can operate at a cell voltage of 1.9 V, much larger than the decomposition voltage of water. Moreover, the flexible structure, and reversible and fast redox reactions of both the anode and cathode make the aqueous HICs display a maximum energy density of 48.6 W h kg−1 and a maximum power density of 19 kW kg−1, as well as a long-cycle lifetime with a decay of 0.00172% per cycle.

Metal-free energy storage systems: combining batteries with capacitors based on a methylene blue functionalized graphene cathode

A simple one-step hydrothermal synthesis of cobaltnickel selenide/graphene nanohybrid as an advanced platinum free counter electrode for dye sensitized solar cell

/pdf/pulsed-laser-deposition-of-nise2-film-on-carbon-nanotubes-4mtkq0bgi8.pdf

Pulsed Laser Deposition of NiSe2 Film on Carbon Nanotubes for High-Performance Supercapacitor

Direct growth of high-content 1T phase MoS2 film by pulsed laser deposition for hydrogen evolution reaction

http://www.espublisher.com/uploads/article_pdf/esmm5f112.pdf

Rongrong Nie

Papers

Pulsed Laser Deposition of NiSe2 Film on Carbon Nanotubes for High-Performance Supercapacitor

Direct growth of high-content 1T phase MoS2 film by pulsed laser deposition for hydrogen evolution reaction

Ultrathin MoSe2 Nanosheets Coated on Hollow Carbon Spheres as Efficient Hybrid Catalyst for Hydrogen Evolution Reaction

MOF-derived cobalt-embedded nitrogen-doped mesoporous carbon leaf for efficient hydrogen evolution reaction in both acidic and alkaline media

Tuning the active sites in the cobalt-based nitrogen-doped carbon by zinc for enhancing hydrogen evolution reaction