The Counter Electrode Impact on Quantum Dot Solar Cell Efficiencies

The counter electrode (CE), despite being as relevant as the photoanode in a quantum dot solar cell (QDSC), has hard-ly received the scientific attention it deserves. In this study, nine CEs: single walled carbon nanotubes (SWCNTs), tungsten oxide (WO3), poly(3,4-ethylenedioxythiophene) (PEDOT), copper sulfide (Cu2S), candle soot, functionalized multiwalled carbon nanotubes ( F- MWCNTs), reduced tungsten oxide (WO3-x), carbon fabric (C-Fabric), and C-Fabric/WO3-x were prepared by using low cost components and facile procedures. QDSCs were fabricated with a TiO2/CdS film which served as a common photoanode for all CEs. The power conversion efficiencies (PCEs) were: 2.02, 2.1, 2.79, 2.88, 2.95, 3.78, 3.66, 3.96, and 4.6 % respectively, and the incident photon to current conversion efficiency re-sponse was also found to complement the PCE response. Among all CEs employed here, the C-Fabric/WO3-x outper-forms all the other CEs, for the synergy between C-Fabric and WO3-x comes to the fore during cell operation. The (i) low sheet resistance of C-Fabric, and its’ high surface area due to the mesh like morphology, enables high WO3-x load-ing during electrodeposition, and (ii) the good electrocatalytic activity of WO3-x, the very low overpotential and its high electrical conductivity that facilitate electron transfer to the electrolyte, are responsible for the superior PCE. WO3 based electrodes have not been used till date in QDSCs; the ease of fabrication of WO3 films, and their good chem-ical stability and scalability also favor their application to QDSCs. Futuristic possibilities for other novel composite CEs are also discussed. We anticipate this study to be useful for a well-rounded development of high performance QDSCs

Corrosion of chromia-forming and alumina-forming ferritic stainless steels under dual atmosphere exposure conditions

The surface morphology and chemistry of oxide scales formed on select chromia-forming and alumina-forming ferritic steels have been studied after exposure to a dual atmosphere of hydrogen and air. Localized Fe-rich oxide nodules with surface whiskers/platelets form at the onset of corrosion. The initiation and growth of localized nodules and breakdown of passivation are attributed to the presence of hydrogen, inclusion of iron oxide in the passivating scale, and subsequent growth of iron-rich oxide due to the establishment of redox (H2-H2O) atmosphere and modification of oxide defect chemistry

Controlled thermal pre-treatment of ZMG232G10® for corrosion mitigation under simulated SOFC interconnect exposure conditions

The IT-SOFC candidate interconnect material ZMG232G10® was thermally pre-treated in air and in H2 – 3% H2O to mitigate dual atmosphere corrosion. Bare and pre-treated steel samples were exposed to a dual atmosphere exposure condition (dry air/metal/4% H2 – N2 (bal.) + 3% H2O) for 500 h at 600 °C. Corrosion products and oxide morphology developed on the air-exposed surfaces were analyzed. Pre-treatments of the metal in oxidizing (air) and reducing (H2 – 3% H2O) gas atmospheres provide improved passivation against dual atmosphere corrosion compared to bare steel. The uniform and iron-free oxide scale developed during the pre-treatment of alloy in the low pO2 H2 – 3% H2O gas atmosphere provides an effective diffusion barrier against the outward transport of cations and oxidation of iron observed under dual atmosphere conditions

Stability of Proton-Conducting Solid Oxide Electrolyzers for Hydrogen Production and Energy Storage

Proton-conducting solid oxide electrolyzers (H-SOEs) provide promising opportunity to produce pure and dry hydrogen in steam electrolysis at relatively low operating temperatures (550-700˚C) utilizing electricity and heat generated from renewable energy sources. Compared to traditional high temperature (750-1000˚C) oxygen-conducting solid oxide electrolyzers (O-SOEs), lower operating temperature of H-SOE offers ease of thermal management, active stack and BOP materials cost reduction and reduction in chromium evaporation from metallic components. Like O-SOEs, preserving the long-term stability of H-SOEs is one of the technical challenges for large-scale hydrogen production. In this technical contribution, results of experimental evaluation of H-SOEs under real-world operating conditions are presented. As fabricated and posttest cells have been characterized using operando electrochemical impedance spectroscopy, X-ray diffraction, focused ion beam-transmission electron microscopy and other bulk and surface characterization techniques to examine bulk, surface and interface stability of electrochemically active components. Phase and morphological changes, compositional uniformity and interfacial reaction products formation have been examined. Electrolyte/electrode materials stability, cell and gas seal fabrication processes, and gaseous impurities affecting long-term electrochemical performance will be discussed. H-SOE electrochemical performance model based on cell materials and operating conditions has been proposed and validated based on single cell testing data