Thomas Gill: Catalytic Materials for Solar Water Oxidation
Solar water-splitting technology can be leveraged to produce fuels and valuable chemicals in an environmentally friendly manner. Though oxygen is the most commonly studied anodic product in this process, hydrogen peroxide has garnered attention as an alternative due to its potential applications as a fuel and water purifying agent. Our work demonstrates that doping bismuth vanadate (BVO) with gadolinium (Gd) reduces the overpotential needed to produce hydrogen peroxide by over 30%, improves catalytic lifetime by a factor of 20, and achieves a faradaic efficiency of ~100% under illumination. Ultimately, gadolinium is shown to drastically improve the activity, selectivity, and stability of BVO, providing a significant step toward the realization of photoelectrochemical hydrogen peroxide as a technology which can address global water and energy demands.
David Mackanic: Design of Polymers for Flexible and Stretchable Lithium Ion Batteries
Batteries for wearable electronics should be safe, flexible, and robust. Solid-state batteries based on solid or gelled polymer electrolytes have the potential to fulfill these criteria. However, many current electrolyte architectures in solid-state batteries utilize polymers that are weak or easily deformable. We employ rational polymer design and synthesis to create a series of extremely tough elastomers with remarkably high lithium-ion conductivity. The catalogue of ion conducting elastomers (ICEs) are created by varying the strength of polymer-polymer interactions within the electrolyte. In their optimal configuration, the gelled ICEs can be stretched elastically to over 30x their original length and have an ionic conductivity of 2E-4 at 25C. We observed that controlling polymer-polymer interactions allows for de-coupling of ion transport from the mechanical robustness of the films. We demonstrate the application of ICEs in a quasi-solid-state battery configuration. Successful operation of such a battery is demonstrated at conditions that mimic those of wearable electronics.
Nate Wolf: Effects of Pressure on Halide-Perovskite Solar-Cell Absorbers
Metal halide perovskites are semiconducting materials which recently gained distinction for their promising optical and electronic properties. Our research focuses on a stable, non-toxic perovskite alternative, Cs2SnIVI6, which unexpectedly has high conductivity and low band gap despite its crystallographically disconnected structure. In our work, we systematically tune this crystallographic disconnection by compressing and expanding the distance between metal halide octahedra using two strategies: high-pressure diamond anvil cell compression and chemical substitution of bulky cations. We track optical and electronic properties as a function of interoctahedral distance to better understand the unique properties of Cs2SnIVI6.
Dianne Xiao: CO2 Utilization for Carboxylic Acid Synthesis
The development of new, scalable CO2 utilization strategies could transform CO2 from a waste product and greenhouse gas into a valuable commodity chemical precursor. Carboxylic acids are attractive targets because they have numerous high-volume applications and their synthesis from petroleum hydrocarbon feedstocks requires difficult and costly oxidations. However, current hydrocarbon carboxylation strategies all consume stoichiometric amounts of an energy-intensive promoter (e.g. strong base or Lewis acid) and strong acid (e.g., HCl). In contrast, Dr. Xiao will present a semi-continuous cycle catalyzed by M2CO3/TiO2 that converts aromatic hydrocarbons into their carboxylic acid or methyl ester derivatives (e.g., benzene to methyl benzoate), without generating any stoichiometric waste.
Free and open to all.