Doping nonmetal atoms into layered transition metal dichalcogenide MX2 structures has emerged as a promising strategy for enhancing their catalytic activities for the hydrogen evolution reaction. In this study, we developed a new and efficient one-step approach that involves simultaneous plasma-induced doping and exfoliating of MX2 bulk into nanosheets–such as MoSe2, WSe2, MoS2, and WS2 nanosheets–within a short time and at a low temperature (ca. 80 °C). Specifically, by utilizing active plasma that is generated with an asymmetric electrical field during the electrochemical reaction at the surface of the submerged cathode tip, we are able to achieve doping of nitrogen atoms, from the electrolytes, into the semiconducting 2H-MX2 structures during their exfoliation process from the bulk states, forming N-doped MX2. We selected N-doped MoS2 nanosheets for demonstrating their catalytic hydrogen evolution potential. We modulated the electronic and transport properties of the MoS2 structure with the synergy of nitrogen doping and exfoliating for enhancing their catalytic activity. We found that the nitrogen concentration of 5.2 atom % at N-doped MoS2 nanosheets have an excellent catalytic hydrogen evolution reaction, where a low overpotential of 164 mV at a current density of 10 mA cm–2 and a small Tafel slope of 71 dec mV–1–much lower than those of exfoliated MoS2 nanosheets (207 mV, 82 dec mV–1) and bulk MoS2 (602 mV, 198 dec mV–1)–as well as an extraordinary long-term stability of >25 h in 0.5 M H2SO4 can be achieved.

A novel redox gel polymer electrolyte based on redox additive, phloroglucinol, incorporated PVA–LiClO4 and graphene nanosheet-based electrodes for symmetrical supercapacitors.

With the goal of obtaining sustainable earth-abundant electrocatalyst materials displaying high performance in the hydrogen evolution reaction (HER), here we propose a facile one-pot plasmainduced electrochemical process for the fabrication of new core−shell structures of ultrathin MoS 2 nanosheets engulfed within onion-like graphene nanosheets (OGNs@MoS 2 ). The resultant OGNs@MoS 2 structures not only increased the number of active sites of the semiconducting MoS 2 nanosheets but also enhanced their conductivity. Our OGNs@MoS 2 composites exhibited high HER performance, characterized by a low overpotential of 118 mV at a current density of 10 mA cm −2 , a Tafel slope of 73 mV dec −1 , and long-time stability of 10 5 s without degradation; this performance is much better than that of the sheet-like graphene-wrapped MoS 2 composite GNs@MoS 2 (182 mV, 82 mV dec −1 ) and is among the best ever reported for composites involving MoS 2 and graphene nanosheets prepared through a simple one-batch process and using a low temperature and a short time for the HER. This approach appears to be an effective and simple strategy for tuning the morphologies of composites of graphene and transition metal dichalcogenide materials for a broad range of energy applications.

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The aim of this study is to prepare a two-dimensional (2D) WO 3 ·H 2 O nanostructure assembly into a flower shape with good chemical stability for electrochemical studies of catalyst and energy storage applications. The 2D-WO 3 ·H 2 O nanoflowers structure is created by a fast and simple process at room condition. This cost-effective and scalable technique to obtain 2D-WO 3 ·H 2 O nanoflowers illustrates two attractive applications of electrochemical capacitor with an excellent energy density value of 25.33 W h kg –1 for high power density value of 1600 W kg –1 and good hydrogen evolution reaction results (low overpotential of 290 mV at a current density of 10 mA cm –2 with a low Tafel slope of 131 mV dec –1 ). A hydrogen evolution reaction (HER) study of WO 3 in acidic media of 0.5 M H 2 SO 4 and electrochemical capacitor (supercapacitors) in 1 M Na 2 SO 4 aqueous electrolyte (three electrode system measurements) demonstrates highly desirable characteristics for practical applications. Our design for highly uniform 2D-WO 3 ·H 2 O as catalyst material for HER and active material for electrochemical capacitor studies offers an excellent foundation for design and improvement of electrochemical catalyst based on 2D-transition metal oxide materials.

In this study, the effect of oxygen vacancy in the CoMn2O4 on pseudocapacitive characteristics was examined, and two tetragonal CoMn2O4 spinel compounds with different oxygen vacancy concentrations and morphologies were synthesized by controlling the mixing sequence of the Co and Mn precursors. The mixing sequence was changed; thus, morphologies were changed from spherical nanoparticles to nanoflakes and oxygen vacancies were increased. Electrochemical studies have revealed that tetragonal CoMn2O4 spinels with a higher number of oxygen vacancies exhibit a higher specific capacitance of 1709 F g−1 than those with a lower number of oxygen vacancies, which have a higher specific capacitance of 990 F g−1. Oxygen vacancies create an active site for oxygen ion intercalation. Therefore, oxidation–reduction reactions occur because of the diffusion of oxygen ions at octahedral/tetrahedral crystal edges. The solid-state asymmetric pseudocapacitor exhibits a maximum energy density of 32 Wh-kg−1 and an excellent cyclic stability of nearly 100%.

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In this paper, a unique method for one-step surface-plasma-induced exfoliation of a graphite/bulk transitional-metal dichalcogenide (TMD) bilayer for the preparation of graphene (Gs)/TMD nanosheet composites is presented, using Gs−tungsten disulfide (WS 2 ) nanocomposites that functioned as electrocatalysts for the hydrogen evolution reaction (HER) as our case study. This approach of producing nanocomposites is universal for all TMD materials with a graphite substrate layer that generates surface plasma when serving as the cathode under 65 V in a 1 M H 2 SO 4 or KOH electrolyte at 90 °C for 50 min. After characterizing the resultant binary nanocomposites, we found that the optimal HER performance occurred for the resultant binary nanocomposites (GW3−H 2 SO 4 ) that is produced from a graphite/bulk WS 2 bilayer (thickness ratio 0.13:0.03 mm) with 1 M H 2 SO 4 as the electrolyte; it has a low overpotential of 180 mV at a current density of 10 mA cm −2 with a low Tafel slope of 76 mV dec −1 and with high stability up to 30 h. This cost-effective and scalable one-step techniquecombining two dissimilar two-dimensional nanostructured compositesfor electrocatalytic applications appears to be an efficient means of fabricating Gs/TMD nanosheet composites suitable for use as HER electrocatalysts.