No abstract

Redox flow batteries (RFBs) are ideal for large-scale, long-term energy storage applications. However, the limited solubility of most ions and compounds in aqueous and non-aqueous solvents (1-1.5 M) restricts its use in the days-energy storage scenario, which necessitates a huge volume of solution in the numerous tanks and the vast floorspace for these tanks, making an RFB systems costly. To resolve the low energy storage density issue, this work presents a novel way in which the reactants and products are stored in both solid and soluble forms and only the soluble ions are circulated through the batteries. Storing the active ions in solid form can greatly increase the storage energy density of the system. With a solid to liquid storage ratio of 2:1, for example, the energy density of the electrolyte of vanadium sulfate (VOSO4), an active compound used in the all-vanadium RFB, can be increased from 40 Ah L-1 to 163 Ah L-1 (>4X), allowing an existing 6-hr RFB system to become a 24-hr system with minimal modifications. To show how the concept works, an H2-V flow battery with a solid/liquid storage system is used, and its successful demonstration validates the solid-liquid storage concept.

a b s t r a c tThree p-A-porphyrins containing long alkoxyl chains attached to the ortho position of phenyl ring and a phenyl carboxylate acid or acrylic acid at the meso position of porphyrin were synthesized. All compounds were characterized by 1 H NMR and mass spectrometry. Optical and electrochemical properties were also obtained. The photovoltaic properties of these p-A-porphyrins were examined for the first time and sensitizers N-1 and N-3 achieved comparable light to electricity conversion efficiencies: 3.94% for N-1 and 4.14% for N-3. However, preparation of N-1 required simple and cost-effective synthesis which made it a promising candidate for the future practical DSSC applications. The low efficiency conversion of N-2 was well explained by the amount of dye loading, IPCE and EIS.

Synthesis and characterization of high electrochemical surface area core-shell RhxSy catalysts for HER/HOR in HBr solution are discussed. Catalysts with RhxSy as shell and different percentage (5%, 10%, and 20%) platinum on carbon as core material are synthesized. Cyclic voltammetry was used to evaluate the Pt- equivalent mass specific ECSA and durability of these catalysts. The results show that the catalyst with core-shell structure has better performance compared to commercial catalyst (RhxSy/C catalyst from BASF). XRD, XPS and TEM were used to characterize the bulk and surface compositions and to confirm the core-shell structure of the catalysts, respectively.