Narrow Results

The cobalt oxide and boron-doped cobalt oxide thin films were produced by spray deposition method. All films were obtained onto glass and fluorine-doped tin oxide (FTO) substrates at 400${}^{\circ }$C and annealed at 550${}^{\circ }$C. We present detailed analysis of the morphological and optical properties of films. XRD results show that boron doping disrupts the structure of the films. Morphologies of the films were investigated by using a scanning electron microscopy (SEM). Optical measurements indicate that the band gap energies of the films change with boron concentrations. The electrochemical supercapacitor performance test has been studied in aqueous 6 M KOH electrolyte and with scan rate of 5 mV/s. Measurements show that the largest capacitance is obtained for 3% boron-doped cobalt oxide film.

In this paper, three-dimensional (3D) Co₃O₄ flower-like microspheres have been successfully synthesized via a facile ethylene glycol (EG)-mediated solvothermal method followed by calcination. The as-prepared flower-like precursors microspheres are formed from the assembly of 2D nanosheets in the presence of hexadecyltrimethylammonium bromide (CTAB). The flower-like architectures of the prepared precursors could be tailored by changing the amount of CTAB. Furthermore, when evaluated as a gas sensor, the obtained Co₃O₄ flower-like microspheres exhibit a good response and sensitivity toward ethanol gas, suggesting their promising potential for gas sensors application.

As one of the electrode materials for supercapacitor, Co₃O₄/graphene composite was mainly synthesized via two-steps method. Here, a facile one-pot method was used for Co₃O₄/graphene composite, and the performances of one-pot-synthesized Co₃O₄/graphene composite were carefully investigated. Liquid-phase exfoliation was used for graphene and the $D$-band/$G$-band ratio of liquid-phase exfoliated graphene was only 0.094, which indicated that the graphene had low defect density and enhanced electrical conductivity. Morphologies investigation of Co₃O₄/graphene composites indicated that Co₃O₄ nanoparticles with mean diameter of 14nm were uniformly anchored on graphene sheets. The facile one-pot method associated with liquid-phase exfoliated graphene induced Co₃O₄/graphene composite with enhanced specific capacitance of 392 F$\cdot$g${}^{-1}$ at a current density of 1 A$\cdot$g${}^{-1}$. The Co₃O₄/graphene composite also expressed relatively small internal resistance and diffusion resistance (0.36$\mathrm{\Omega }$ and 0.45$\mathrm{\Omega }$, respectively). Moreover, the synthesized Co₃O₄/graphene composite yielded excellent rate performances with only 9.5% capacitance loss when current density was increased by a factor of 10.

Developing a general, green and effective strategy to improve the hydrogen evolution reaction (HER) electrocatalyst is urgently needed but challenging. Herein, we report a novel conducting polymer/metal/metal oxide composite as HER catalyst prepared by a two-step strategy, in which the Au/Co₃O₄ is synthesized by a one-pot hydrothermal method, subsequently, cyclic voltammetry is employed to electropolymerize polythionine on the Au/Co₃O₄. It is demonstrated that the HER electrocatalytic activity of Au/Co₃O₄ is effectively improved by the coating polythionine layer. The optimal polythionine/Au/Co₃O₄ displays an excellent electrocatalytic ability towards HER with an overpotential of 168mV at $10\mathrm{\text{mA}}\cdot {\mathrm{\text{cm}}}^{-2}$ and low Tafel slope of 79mV$\cdot$dec${}^{-1}$ in 0.5M H₂SO₄, which is greatly superior to those of the Au/Co₃O₄ (an overpotential of 300mV at $10\mathrm{\text{mA}}\cdot {\mathrm{\text{cm}}}^{-2}$ and tafel slope of $157\mathrm{\text{mV}}\cdot {\mathrm{\text{dec}}}^{-1})$. Interestingly, the HER performance of N-doped reduced graphene (N-rGO) can also be significantly boosted by the coating polythionine layers, indicating the multifunctionality of polythionine in the enhancement of HER performance of nano electrocatalysts.