Improving the electro-catalytic activity of graphene has recently been the subject of intense research for high efficiency flexible energy storage and conversion devices. We report the synthesis of a large scale graphene film by a CVD method and its electro-catalytic activity by functionalization with HNO₃ for a high efficiency electrochemical electrode in DSSCs. We found that HNO₃ functionalization on graphene enhances the tri-iodide reduction rate by three times in a dye sensitized solar cell compared to that of pristine graphene. The X-ray photoelectron spectroscopy (XPS) and ultra-violet photoemission spectroscopy (UPS) studies confirm the covalently attached C–OH, C(O)OH and NO³⁻ moieties to carbon atoms through sp²–sp³ hybridization, and this results in the Fermi level shift towards p-type doping. We believe that the covalently attached functional groups cause the enrichment of the electro-catalytically active sites along with facilitating the charge transfer kinetics from graphene counter electrodes to redox couples. The enhanced catalytic effect of functionalized graphene offers insights into new types of electrode development opportunities in graphene based energy storage and conversion devices.

A copper-and-zinc (Cu–Zn) alloy material was synthesized using a vacuum sealing method, in which evaporated zinc was reacted with copper film or nanoparticles to form a homogeneous Cu–Zn alloy. This alloy was evaluated as an electrocatalyst and/or cocatalyst for photocatalysis to selectively reduce carbon dioxide to formic acid. Based on the optimised alloy composition, the Cu₅Zn₈ catalyst exhibited efficient electrochemical CO₂ reduction. Furthermore, we constructed a photoelectrochemical (PEC) three-electrode system, in which the Cu₅Zn₈ film functioned as the cathode for CO₂ reduction in the dark and strontium titanate (SrTiO₃) served as the photoanode for water oxidation. The PEC system also selectively reduced CO₂ to formic acid with a faradaic efficiency of 79.11% under UV-light and the absence of an applied bias potential. SrTiO₃ particles decorated with nanoparticles of the Cu–Zn alloy also photocatalytically reduced CO₂ to formic acid under UV-light. Isotope trace analysis demonstrated that water served as the electron donor to produce oxygen and organic molecules under UV light, similar to photosynthesis in plants. The Cu–Zn alloy material developed in the present study is composed of ubiquitous and safe materials, and can catalyse CO₂ conversion by means of various kinds of renewable energies.

A visible-light-sensitive tin sulfide photocatalyst was designed based on a ubiquitous element strategy and density functional theory (DFT) calculations. Computational analysis suggested that tin monosulfide (SnS) would be more efficient than SnS₂ as a photocathode for hydrogen production because of the low ionization potential and weak ionic character of SnS. To test this experimentally, nanoparticles of SnS were loaded onto a mesoporous electrode using a wet chemical method, and the bandgap of the synthesized SnS quantum dots was found to be tunable by adjusting the number of successive ionic layer adsorption and reaction (SILAR) cycles, which controls the magnitude of the quantum confinement effect. Efficient hydrogen production was achieved when the bandgap of SnS was wider than that of the bulk form.