Poster Session 6

ABSTRACT:

In this work, the effect of alkali treatments namely Na and RbF has been investigated on the potential induced degradation (PID) for CdS/CIGS solar cells. Four device types with variations in Na content and RbF post-deposition treatment (PDT) have been studied. Baseline Na devices (Type 1) show an average efficiency of ~18% which does not show an improvement with RbF-PDT (Type 1R) in this sample series. Low Na devices with and without RbF-PDT both show average efficiency of ~16% for this sample series. PID tests were conducted in dark at temperatures between RT- 85 °C under 1000 V applied between back of the soda-lime glass and the Mo contact. All device types show degradation due to increase in shunt-conductance, which could be partially recovered by reversing the bias voltage polarity. Recovery of PID degradation is a temperature-dependent phenomenon, wherein, higher recovery is observed at a higher temperature. Preliminary results show low-Na devices recover to 80%, whereas, baseline Na devices recover to 50% of initial efficiency at 85 °C. RbF-PDT does not change the recovery of baseline Na devices, however, low-Na devices with RbF-PDT show recovery to only 25% of initial device efficiency.

ABSTRACT:

Biochar (BC) is a biomass-derived black carbon with interconnected networks of micropores, which is an economical substitute for conventional adsorbents, such as activated carbon. In this study, we investigated the effect of physical and chemical modifications on the surface area, hydrophilicity, functional groups, and surface morphology of walnut biochar. The BC used here is prepared through pyrolysis at a temperature of 900 °C in an argon gas inert environment. Then, the BCs are modified using hydrochloric acid (HCl), Potassium Hydroxide (KOH), and DI water to be subsequently used for remediation of chlorinated hydrocarbons such as trichloroethylene (TCE) and Perchloroethylene (PCE). After modification, the different biochars are characterized using Scanning Electron Microscopy (SEM), Fourier Transform Infrared (FTIR) spectroscopy, Contact Angle measurements, and Brunauer-Emmett-Teller (BET) characterizations. The results can advance the understanding of different modification effects on BCs’ properties, aiming at the wide adoption of cost-effective and eco-friendly adsorbents.

ABSTRACT:

In order to meet the increasing global demand for electricity and reduce global carbon emissions, it is essential to shift our energy system away from fossil fuel towards renewable energy sources. Since the booming research on “perovskite” solar cell technology, perovskite materials have obtained immense research interest owing to their promising photovoltaic properties and rapid growth in efficiency from 3.8% to 25.7% achieved from fundamental research just within a decade. Their ability to be synthesized atmospherically with a low cost and wide range of compositional variety make them favorable to study. Owing to their higher stability, greater efficiency, and lesser toxicity they show the immense possibility to replace the conventional silicon solar cells. Our present work aims at analyzing the effect of different additives, such as pyrazine and GuaSCN in the fabrication and development of highly efficient and stable lead-free nontoxic Cs₂SnI₆ perovskite material. Our result shows pyrazine and GuaSCN generate low bandgap (~1.2-1.3 eV) perovskite films and assist in higher photon absorption capability within the range of 400 nm -700 nm of visible light wavelength, compared to the samples with no additive present. Our X-ray diffraction analysis (XRD) shows these additives help in the formation of cubic Cs₂SnI₆ perovskite with very less CsI impurity present. Samples with additives tend to have similar X-ray diffraction patterns before and after heat treatment in the dark confirming their ability to block degradation and maintain high stability even after 100 hours of heat exposure at 65 °C.

ABSTRACT:

Haloacetonitriles (HANs) are unwanted nitrogenous disinfection byproducts (DBPs) generated during the disinfection of water with free chlorine (Cl2) or chloramine (CLM). Even though HAN precursors have been discovered in a variety of water sources and have greater toxicity than their regulated counterparts, much remains unknown about which chemicals act as HAN precursors. The widespread consumption of antibiotics and use of pesticides/herbicides/insecticides in agriculture has resulted in their presence in surface and groundwater. Furthermore, those chemicals that are not entirely eliminated by water or wastewater treatment may create DBPs during subsequent disinfection. Therefore, it is important to know the role of antibiotics and agrochemicals as HAN precursors. Formation potential (FP) testing is commonly used as an indirect assessment of DBP precursors in a source water or to assess the potential (i.e., formation yield) of a particular chemical to form DBPs. As a representative of pesticides/herbicides/ insecticides, atrazine, carbaryl, and simazine were chosen; all have a secondary amine group with an aromatic nitrogen ring. For antibiotics, sulfanilamide, sulfisoxazole, and sulfacetamide with a sulfonamide functional group attached to an aniline group were chosen. Each compound was reacted with chlorine and chloramine at specific test conditions to find out its potential as an HAN precursor. Overall, this study will increase our understanding of HAN precursors, and could lead to changes in water treatment techniques, policy changes or removal of a chemical from the market if it has a high potential to form HANs.

ABSTRACT:

Nuclear power is a clean, reliable source of energy that can help mitigate the effects of global climate change. Concerns over safety and waste are often associated with the use of nuclear power. Generation IV Molten Salt Reactors (MSRs) eliminate a major nuclear safety concern, core meltdowns, and can consume used nuclear fuel waste. However, information regarding some fundamental characteristics of molten salt fuel systems are yet to be fully established. Electrochemistry is a highly-selective method for determining values like formal potentials and diffusion coefficients based on spectroscopic responses to applied potentials. Boron doped diamond (BDD) material is predicted to be a resilient electrochemical tool in high-temperature, radioactive molten salts given its inert nature and the strength of the sp³ carbon-carbon bonding within a single crystal. In this study, we investigated the redox behavior of stable Eu (as EuCl₃, III/II) as a non-radioactive surrogate for U-238 (as UCl₃ or UCl₄, IV/III) in chloride molten salt systems using electrochemical techniques with BDD. Cyclic voltammetry (CV) was used to determine the following redox properties: formal reduction potential (E°’), peak separation (ΔE), electron transfer stoichiometry (n), diffusion coefficient (D), and electron transfer rate constant (k). We also studied the resulting corrosion of the BDD electrodes over prolonged exposure to the chloride molten salts at different temperatures. The BDD material has been shown to withstand molten chloride solvent salts at 500 °C over hundreds of hours based on electrochemical response comparisons and topographical analyses, informing future experiments with uranium(III/IV) chloride and fluoride. This work advances the understanding of the chemistry of a Gen IV nuclear reactor like the MSR, while again proving the applicability of BDD as electrode material for harsh environments.