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Cobalt-based heterogeneous cocatalysts are important substitutions of noble metal cocatalysts in many important commercial chemical processes, but their efficiency is extremely low on a per metal atom basis, because only the atoms located at surface active-sites participate in the chemical reaction. Thus, cocatalysts with small cluster dispersions are highly desirable to maximize the amount of active-sites and enhance the per atom efficiency. Here, we report the synthesis of sub-nanometer CoO clusters which are anchored to 2D ultrathin TiO(B) nanosheets, as a cocatalyst for H evolution reaction (HER). It was found that the conduction type of CoO clusters turns from P-type to N-type, and the heterojunction band structure between TiO(B) and CoO clusters changes from type II to type I, when the cluster size is reduced from nanometer scale to the sub-nanometer scale. With a suitable energy band matching between TiO(B) and sub-nanometer CoO clusters, the electrons generated in TiO(B) during the photocatalytic process reduce the Co ions into metallic Co atoms, which produce excellent photocatalytic stability and extremely high HER efficiency comparable to that of the noble Pt cocatalyst.

We present a novel hybrid electrodes based on reduced graphene oxide/nickel/zinc oxide heterostructures. The sensor was fabricated by template-free hydrothermal growth of ZnO nanorod arrays on conductive glass substrates (FTO) followed by conformal electrodeposition of nickel nanoparticles with an average size of 18 nm. Then, in-situ reduction and electrophoretic deposition of graphene oxide (GO) nanosheets on the structured ZnO/Ni electrode was performed. The prepared three-dimensional nanostructure exhibited fast electrocatalytic response (<3s) towards glucose oxidation due to the large surface area and high electro-activity. The prepared biosensor possessed a wide linear range over 0.5 μM to 1.11 mM, a low detection limit of 0.15 μM at signal/noise ratio (S/ N) of 3, and a sensitivity of 2030 µAcm-2 mM-1. Therefore, the performance of the sensor regarding the detection limit and sensitivity is better than many other electrodes utilized for non-enzymatic glucose detection. No interference from different electroactive substances such as uric acid and ascorbic acid is also noticed. The potential application of the 3D hybrid biosensors for detection of glucose in real human serum samples is shown. This novel structured electrode holds great promise for the development of biosensors and other electrochemical devices.

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