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Among various types of alternative energy devices, solid oxide fuel cells (SOFCs) operating at low temperatures (300‐600°C) show the advantages for both stationary and mobile electricity production. Proton‐conducting oxides as electrolyte materials play a critical role in the low‐temperature SOFCs (LT‐SOFCs). This review summarizes progress in proton‐conducting solid oxide electrolytes for LT‐SOFCs from materials to devices, with emphases on (1) strategies that have been proposed to tune the structures and properties of proton‐conducting oxides and ceramics, (2) techniques that have been employed for improving the performance of the protonic ceramic‐based SOFCs (known as PCFCs), and (3) challenges and opportunities in the development of proton‐conducting electrolyte‐based PCFCs.

 

The unique chemical and physical properties of graphene and its derivatives (graphene oxide, heteroatom‐doped graphene, and functionalized graphene) have stimulated tremendous efforts and made significant progress in fuel cell applications. This review focuses on the latest advances in the use of graphene‐based materials in electrodes, electrolytes, and bipolar plates for fuel cells. The understanding of structure‐activity relationships of metal‐free heteroatom‐doped graphene and graphene‐supported catalysts was highlighted. The performances and advantages of graphene‐based materials in membranes and bipolar plates were summarized. We also outlined the challenges and perspectives in using graphene‐based materials for fuel cell applications.

 

Highly efficient capacitive deionization (CDI) relies on unimpeded transport of salt ions to the electrode surface. Graphene is an ideal candidate to provide superb conditions for ion adsorption as it possesses high theoretical surface area and electrical conductivity. When ions are stored solely within the electric double layers (EDLs), a hydrophilic graphene surface with hierarchical pores can maximize the accessible surface area and promote the ion transport. In the case of synergistic ion storage via electrostatic adsorption and faradaic redox reaction, graphene can act as both the electron highway and the reciprocal spacer to provide surface-confined effects. Substantially, structural and chemical engineering towards graphene can enhance the ion removal capacity and rate, and improve the charge efficiency and ion selectivity. In this review, we keep pace with the in-depth studies of CDI technologies and recent progress on graphene-based materials for CDI. Major challenges in the rational assembly of the desired material functionalities in terms of surface area, pore structure, and hydrophilicity are addressed. As electrode materials develop, the ultimate goal is to achieve highly efficient, energy-saving, and environment-friendly CDI. 

Steam reforming of methane (SRM) is one of the most important industrial processes, which produces 95% of hydrogen used in the USA. However, SRM is an endothermic reaction, which requires a high energy input and a high reaction temperature (>800 °C) for the current process. Furthermore, its products must be subjected to a water–gas shift (WGS) process. A photocatalytic process is expected to solve the energy issue and to eliminate the necessity of WGS for SRM. However, the hydrogen yield from the current photocatalytic steam reforming of methane (PSRM) is very low (μmol h −1 g −1 level), which is far below industrial interest. This work demonstrates that a Pt/blackTiO 2 catalyst dispersed on a light-diffuse-reflection-surface is excellent for efficient visible-light PSRM. Under visible light illumination on the catalyst by filtering UV light from AM 1.5G sunlight, CH 4 and H 2 O were directly converted into H 2 and CO 2 without WGS, leading to a high H 2 yield of 185 mmol h −1 g −1 with a quantum efficiency of 60% at 500 °C. The yield is 3 orders of magnitude larger than the reported values, which can be attributed to the synergistic effect between potential and kinetic energies. This opens up a new opportunity for hydrogen production from water and natural gas using solar energy.