| To deal with the problem of creating sustainable energy solutions, Electrochemistry will play a vital role, particularly in the conversion and storage of electrical into chemical energy or the reverse conversion and storage. Electrochemical water splitting is used as the initial reaction for hydrogen green economy. However, during the water splitting, the oxygen evolution reaction(OER) at the anode suffers from sluggish kinetics, which limits the overall rate efficiency of water splitting. Therefore, it’s very essential to develop high efficiente O ER electrocatalysts, particularly with earth-abundant and inexpensive materials. Focuses on this point, this paper summarized the development on OER electrocatalysts, expounding on the designing and synthesis novel Co based catalysts. However, the non-noble metal electrocatalysts at present cannot reach the demand for practical application. Based on this problem, we choose to design and synthesize cheap, robust, and efficient Co based materials as OER electrocatalysts, or composite the Co-based composite with conductive carbon supporting materials to improve the catalytical performance. In this paper, we also study the effect of crystal plane and structure on the OER activity. T he main research results obtained of this paper are listed as follows:Co3O4 nanorods-multiwalled carbon nanotubes hybrid(Co3O4@MWCNT) has been rationally designed and synthesized with the assistance of DETA, and this cheap and easily prepared electrocatalyst showed highly efficient OER activity in alkaline electrolyte. The well-defined Co3O4 nanorods uniformly anchored onto mildly oxidized MWCNTs present a mace shape. The OER tests showed that the effect of EDTA on the morphology and catalytical performance of the Co3O4@MWCNT is very clear and important, and the Co3O4@MWCNT hybrid exhibited more prominent catalytic activity towards oxygen evolution reaction(O ER) than Co3O4-MWCNT which without EDTA during synthesis process. This work offers a strategy for rational design and synthesis efficient metal oxide/MWCNT composite with special structure.In the above work, the HRTEM showed that the mainly exposed plane of the Co3O4 nanorods is {110}, which is composed mainly by Co3+, so we hypothesis Co3+ might be the active sites for OER. Focuses on this point, we synthesized Co3O4 nanorods and nanocubes with different dominant exposed planes({110} and {100} respectivly), and then investigated the plane effects of Co3O4 nanocrystalline on the OER activity. Results show that the surface Co3+ species of the Co3O4 crystal should be the active sites for OER catalysis. This work is meaningful for rational design and synthesis of metal oxides with more active plane exposed for efficient OER electrocatalysts.In this section, mesoporous Co3O4 with sheet and cube sugar shape are successfully synthesized with facile hydrothermal method, and without using any surfactants or template. Unusually, we added the alkali(NaOH and Na2CO3) in particle source, the mesoporous Co3O4 synthesized by this ―naturally precipitation‖ method showed enhanced OER performance than the normal Co3O4 particle, moreover, the mesoporous Co3O4 with sheet like performed the better OER activity than cube sugar-shaped catalyst, we think the ultrathin sheet with mesoporous is more convenient for ―inside surface‖ Co to contact with electrolyte and the evolution of O2 when compared with the sugar-shaped mesoporous Co3O4.Cobalt carbonate hydroxide hydrate(CCHH) is mainly used as precursor for Co3O4, and it is nearly not applied for electrocatalyst. As for its poor conductivity, we anchored CCHH nanosheets onto mildly oxidized multiwalled carbon nanotubes, and the resulted hybrid(CCHH/MWCNT) is used as high efficient electrocatalyst for water oxidation. This work not only provides a novel cobalt-based electrocatalyst for oxygen evolution, but also offers a useful and viable approach to deliberately synthesize functional nanocomposites for applications in energy conversion and storage. |
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