Huiqing Fan

Surfactant-assisted photochemical deposition of three-dimensional nanoporous nickel oxyhydroxide films and their energy storage and conversion properties

Three-dimensional (3D) nanoporous nickel oxyhydroxide (NiOOH) films were prepared on a TiO2 nanoarray substrate by a novel surfactant-assisted photodeposition method using Ni2+-containing solutions as precursors, and their energy storage and conversion behaviors were investigated. In the photodeposition process, photogenerated holes were used to oxidize Ni2+ ions to Ni3+ ions, resulting in the precipitation of NiOOH onto the TiO2 nanoarray substrate. The amount of photochemically deposited NiOOH increased with an increase in the surfactant (sodium lauryl sulfate, SDS) concentration in the deposition solution. If the SDS concentration did not surpass 0.3 wt%, the photochemically deposited NiOOH composite film exhibited a 3D nanoporous structure, and the pore size decreased with an increase in the SDS concentration. The 3D nanoporous NiOOH composite film which was prepared by photodeposition for 5 h in the presence of 0.3 wt% SDS presented the largest discharge capacity in our experimental range, implying enhanced UV-induced oxidative energy storage. The as-photodeposited NiOOH nanoflakes with a quasi two-dimensional structure exhibited close contact with TiO2 nanorods, originating from the fact that NiOOH was deposited at the sites where the photogenerated holes were available. It was demonstrated that the as-photodeposited 3D nanoporous NiOOH composite film could be used for the removal of trace amounts of indoor formaldehyde gas, which was mainly due to the stored oxidative energy. The photodeposition method demonstrated here can be used as a general route to fabricate photocatalyst-based composite materials.

Facile morphology controlled synthesis of nanostructured Co3O4 films on nickel foam and their pseudocapacitive performance

Nanostructured transition metal oxides are a current investigation focus for supercapacitors. We herein report a facile solvothermal synthesis of nanostructured Co3O4 films on nickel foam. The morphologies and dimensions of the Co3O4 films can be effectively tuned by tailoring the solvent compositions in the solvothermal reaction solutions. The effect of solvent composition on the morphologies of nanostructured Co3O4 films is analyzed. The 3D hierarchically porous Co3O4 network film, which is synthesized in the solvothermal reaction solution with an intermediate ethylene glycol/water volume ratio (1 : 29), shows a markedly enhanced pseudocapacitive performance. The specific capacitances of the Co3O4 network film electrode at the current densities of 0.870 and 17.391 A g−1 are 2817 and 1948 F g−1, respectively, revealing its large specific capacitance and excellent rate capability. Furthermore, the Co3O4 network film electrode exhibits good electrochemical cycling stability with a specific capacitance of 1628 F g−1 after 3500 cycles at a current density of 4.348 A g−1. The prominent pseudocapacitive performance of the Co3O4 network film electrode can be attributed to its unique structural characteristics. The as-synthesized 3D hierarchically porous Co3O4 network film with excellent pseudocapacitive performance demonstrates promising potential as a high-performance electrode for supercapacitors.