Thomas Gill: Catalytic Materials for Solar Water Oxidation
Solar water-splitting is a technology which 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 Solid Polymer Electrolytes for Lithium Ion Batteries
Solid polymer electrolytes (SPEs) promise to improve the safety and performance of lithium ion batteries (LIBs). However, the low ionic conductivity and transference number of conventional poly(ethylene oxide) (PEO) based SPEs preclude their widespread implementation. Herein, we introduce crosslinked poly(tetrahydrofuran) (xPTHF) as a promising polymer matrix for “beyond PEO” SPEs. Molecular Dynamics and DFT simulations accompanied by 7Li NMR measurements show that the lower spatial concentration of oxygen atoms in the xPTHF backbone leads to loosened O-Li+ coordination. This weakened interaction enhances ion transport; xPTHF has a high lithium transference number of 0.53 and higher lithium conductivity than a xPEO SPE of the same degree of polymerization at room temperature.
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.
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Stanford, CA 94305
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