| With the developments of society and technology, the activities of human being are highly dependent on the consumption of fossil fuels. However, the limited reserves and the environmental contamination caused by overusing the fossil fuels urge the scientists to develop sustainable clean energy carrier and high-performance energy storage systems. Aiming at producing clean energy carrier (hydrogen) with low energy consumption and stable fabricating supercapacitor electrodes with high and stable performance, we employed a series of synthetic methods to obtain well-aligned nanomaterials on the surface (i.e. nanoarrays) and investigated the relationship between structures and the energy storage and electrochemically catalytic (hydrogen evolution reaction and oxygen evolution reaction) performances. The research contents and conclusions are shown as following:1. We developed a hydrothermal method to construct vertically aligned one dimensional or two dimensional nano structures of NiO and Ni(OH)2, which showed ultrahigh specific capacitance (>2000 F/g), remarkable rate capability and stability. The high capacitive performance was attributed to the unique nanostructures:a. the nanoarray materials could guarantee a fast electron transfer process due to the direct growth nature, which offered an intimate contact to the current collector; b. the open space between adjust nanostructures created a high porosity, which significantly increased the surface area and facilitated the electrolyte penetration, accelerating the mass-transfer process in the interface; c. inherited from the merits of nanomaterials, the nanosizes of nanoarray materials made them fully exposed in the electrolyte, thus increasing the utilization of nanoarray materials.2. By selectively etching the bimetallic oxides/hydroxides nanoarray, we could obtain a highly porous nanoarray, which exhibits both higher specific capacitance and rate capability. As a typical example, by using a high concentrated NaOH solution to selectively etch the Al part of CoAl layer double hydroxide (CoAl-LDH) nanoarray, a highly porous cobalt hydroxide carbonate nanoarray could be fabricated with a capacitance higher than 1000 F/g, much better than that of CoAl-LDH precursor.3. We developed a multi-step hydrothermal method to hierarchical nanoarray materials, which overcame the problem of limited mass-loading (<3 mg/cm2) on the traditional nanoarrays. The hierarchical nanoarrays offered a mass-loading as high as-12 mg/cm2, which resulted in an ultrahigh areal capacitance (-24.95 F/cm2) and promising practical applications in NiZn batteries.4. We discovered the underwater superaerophobicity of three dimensional nanoarrays, which resulted in a fast current increase and stable working condition when the nanoarrays were used as electrochemical gas evolution reactions. For instance, constructing nanostructured MoS2 film could greatly reduce the adhesion force to the gas bubbles, and possess a gas bubble contact angle larger than 150°. When used in the electrochemical hydrogen evolution reaction, the nanostructured MoS2 film offered a small releasing size of gas bubbles and promoted the gas evolution behavior, resulted in even higher performance than the commercial Pt/C catalyst. Moreover, the "superaerophobic" surface can also be applied in oxygen evolution reaction and direct hydrazine fuel cells. As a result, the NiFe-LDH nanostructured film showed a higher OER performance than commercial Ir/C catalyst and the "superaerophobic" nanostructured Cu film exhibited a 3 times higher performance than commercial Pt/C electrode in direct hydrazine fuel cells.5. We developed an electrochemical tuning method in organic electro hyte to tune the electronic structure of existing catalyst, for further improving the corresponding catalytic performance. It is found that after delithiation process, the LiCo02 was converted to Lio.5Co02, which showed one order high electrocatalytic activity than that of pristine LiCoO2, demonstrating the effectiveness of the electrochemical tuning method. |
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