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Tremendous efforts have been directed to developing reliable electrocatalysts to gain clean hydrogen energy from water splitting and encounter energy challenges. The morphology at the nanoscale of electrocatalysts has also a significant influence on hydrogen evolution reaction. An alkaline-based electrocatalyst, strontium hydroxide hydrate, has been synthesized at temperatures of 80, 140, and 200 °C using the hydrothermal process. The employed growth temperature capably influences the morphology and intrinsic characteristics of the strontium hydroxide hydrate for the hydrogen evolution reaction. The mesoporous nature, greater electrochemical and specific surface area of nanorods, and facile proton donation by the acid jointly enhance the HER activity. Hy-Sr-(OH)2-200 nanorods have exhibited a good overpotential of 84 mV in 0.5 M H2SO4 at the current density of 10 mA cm–2, which is better than the nanopallets (Hy-Sr-(OH)2-80) and the hybrid morphology consisting of nanopallets and nanorods (Hy-Sr-(OH)2-140). The mesoporous nature, greater electrochemical and specific surface area, and nanorod-like morphology have promoted and facilitated the adsorption and desorption of the active hydrogen atoms at the active sites inside the Hy-Sr-(OH)2-200 nanorods. As a result, Hy-Sr-(OH)2-200 nanorods exhibit the Tafel slope of 81 mV dec–1 in 0.5 M H2SO4 and follow the Volmer–Heyrovsky phenomena. Moreover, Hy-Sr-(OH)2-200 nanorods show a good turnover frequency of 142.84 ms–1 at the fixed reversible hydrogen potential of 0.5 V, which is better than the other employed electrolytes and electrocatalysts fabricated at temperatures of 80 and 140 °C. The symmetric system, consisting of Hy-Sr-(OH)2-200 nanorods, shows a good overpotential of 240 mV at a current density of 10 mA cm–2, along with a Tafel slope of 79 mV dec–1 in 0.5 M H2SO4. The electrocatalyst of Hy-Sr-(OH)-2-200 nanorods comprehensively exhibits good performance for the hydrogen evolution reaction. [ABSTRACT FROM AUTHOR]

It is demonstrated that it is possible to coat the individual fibers of wood-based nanocellulose with polypyrrole using in situ chemical polymerization to obtain an electrically conducting continuous high-surface-area composite. The experimental results indicate that the high surface area of the water dispersed material, to a large extent, is maintained upon normal drying without the use of any solvent exchange. Thus, the employed chemical polymerization of polypyrrole on the microfibrillated cellulose (MFC) nanofibers in the hydrogel gives rise to a composite, the structure of which-unlike that of uncoated MFC paper-does not collapse upon drying. The dry composite has a surface area of approximately 90 m(2)/g and a conductivity of approximately 1.5 S/cm, is electrochemically active, and exhibits an ion-exchange capacity for chloride ions of 289 C/g corresponding to a specific capacity of 80 mAh/g. The straightforwardness of the fabrication of the present nanocellulose composites should significantly facilitate industrial manufacturing of highly porous, electroactive conductive paper materials for applications including ion-exchange and paper-based energy storage devices.

Conducting polymers for battery applications have been subject to numerous investigations during the last two decades. However, the functional charging rates and the cycling stabilities have so far been found to be insufficient for practical applications. These shortcomings can, at least partially, be explained by the fact that thick layers of the conducting polymers have been used to obtain sufficient capacities of the batteries. In the present letter, we introduce a novel nanostructured high-surface area electrode material for energy storage applications composed of cellulose fibers of algal origin individually coated with a 50 nm thin layer of polypyrrole. Our results show the hitherto highest reported charge capacities and charging rates for an all polymer paper-based battery. The composite conductive paper material is shown to have a specific surface area of 80 m(2) g(-1) and batteries based on this material can be charged with currents as high as 600 mA cm(-2) with only 6% loss in capacity over 100 subsequent charge and discharge cycles. The aqueous-based batteries, which are entirely based on cellulose and polypyrrole and exhibit charge capacities between 25 and 33 mAh g(-1) or 38-50 mAh g(-1) per weight of the active material, open up new possibilities for the production of environmentally friendly, cost efficient, up-scalable and lightweight energy storage systems.

This work investigates the movement of anions during potentiostatic controlled reduction of novel composite materials consisting of high surface area cellulose substrates, extracted from the Cladophora sp. algae, coated with thin ( approximately 50 nm) layers of the intrinsically conducting polymer (ICP) polypyrrole. The coating was achieved by chemical polymerization of pyrrole on the cellulose fibers with iron(III) chloride and phosphomolybdic acid, respectively. The composites are in the form of paper sheets and can be directly immersed into an electrolyte solution for ion absorption/desorption. The motion of glutamate and aspartate anions during cathodic polarization was investigated as a function of preceding anodic polarization at various potentials. The composite was found to exhibit memory effect as the response to a cathodic polarization of constant magnitude produced different responses depending on the magnitude of the preceding anodic potential. After the application of a cathodic potential to the composite, the reduction current curvesgenerated by anions leaving the compositewere found to initially increase in magnitude followed by a monotonic decay. A similar response has not been described and analyzed for electrochemical reduction of anion containing ICP materials earlier. A theoretical model was developed to aid the analysis of the experimental data. The model accounts for both freely mobile anions and anions that may be temporarily trapped in a contracting PPy network during cathodic polarization. By fitting the recorded reduction current curves to this model, detailed information about the ionic movement in the composite could be obtained, which may be used to further optimize the materials properties of conducting polymer systems aimed for specific electrochemical ion exchange processes.