Session Overview |
Thursday, May 30 |
15:10 |
Energy-Efficient Photo-Electrochemical CO2 Electrolysis to Produce Feedstock Chemicals and Fuels
* Md Golam Kibria, University of Calgary, Canada Photo-Electrochemical CO2 reduction (eCO2R) is one of the emerging approaches to converting CO2 to value-added products using water and renewable electricity. One of the performance metrics for eCO2R is the energy efficiency needed to drive the economic viability of the process. In this talk, I will present the latest developments in our lab in this pacey field. I will give three examples wherein we are improving the efficiency of CO2 electrolysis. In the first example, I will talk about an integrated approach to separate and convert CO2 using a MOF-based Mixed Metrix Membrane (MMM) to ethylene and other feedstock chemicals. Through this process, the CO2 from industrial off-gas can be directly converted to ethylene or CO without requiring a CO2 capture process, significantly reducing the required energy of the process. In the second example, I will talk about how we are utilizing waste (i.e., glycerol) from the biodiesel industry to make fine chemicals and concomitantly reduce the energy required for CO2 electrolysis. In the last example, I will present the latest developments in our efforts to make directly deposited ultrathin solid polymer electrolytes to enable energy-efficient CO2 electrolysis. I will conclude my talk by highlighting the importance of system-level analysis that can guide emerging technologies to make the biggest impact and help transition to our net-zero target. |
15:35 |
Carbon Nitride (CN) Nanosheets and Doped CN Nanoparticles for Photovoltaics, Solar Fuels and Sensing
* Karthik Shankar, University of Alberta, Canada High performance semiconductors constituted of earth abundant elements are much needed to realize the full promise of the green transformation. One particularly promising example is bulk carbon nitride (CN), which is a layered polymeric organic semiconductor constituted by a sp2 hybridized framework similar to graphite. Typical small molecule and polymeric organic semiconductors are vulnerable to heat, moisture and oxygen. On the other hand, CN owing to its graphitic structure, exhibits remarkable chemical, photochemical and thermal stability. The most commonly encountered composition of CN is g-C3N4 which has a wide band gap (Eg) of 2.7 eV. We introduced a nitrogen-rich CN with the composition C3N5, which had a narrow band gap of 1.76 eV. C3N5 outperformed g-C3N4 as an electron transport layer (ETL) in MAPbBr3 based halide perovskite solar cells, and generated a much higher open circuit photovoltage. C3N5 blended with MAxFA1–xPb(I0.85Br0.15)3 active layer passivated traps and improved the photoconversion efficiency of the resulting solar cells. Colloidal nanoparticles (NPs) can be formed from both bulk CN and CN nanosheets. Phosphorus doping of CN NPs narrows the band gap. Photoanodes consisting of TiO2 nanotube arrays decorated with P-doped CN NPs (Eg = 2.1 eV) generated a photocurrent density of 2.54 mAcm-2 under AM1.5G one sun illumination in sunlight-driven water-splitting. A champion hydrogen evolution rate of 22 µmol h−1 corresponding to a Faradaic efficiency of 93.2% was achieved using TiO2 nanotube arrays decorated with P-doped CN NPs. Monolayered graphenic carbon nitride was used to perform in situ surface passivation and stabilization of CsPbBr3 nanocrystals to form core-shell quantum dots which generated a photocurrent density of 1.55 mAcm-2 in photoelectrochemical water-splitting and also successfully reduced CO2 to CO under solar illumination. We synthesized exfoliated 2D nanosheets of a modified carbon nitride constituted of tris-s-triazine (C6N7) linked pyromellitic dianhydride polydiimide (CN:PDI) with a deep oxidative highest occupied molecular orbital (HOMO) position, which ensures sufficient oxidizing power for photogenerated holes in CN. Furthermore, carboxyl-rich g-C3N4 NPs were found to be selective fluorescence quenching sensors for the detection of Ag+ and Ce3+ ions with a detection limit of 30 pM for Ag+ ions. |
16:00 |
Perovskite Photovoltaics: Performance, Upscaling, and Reliability
* Makhsud Saidaminov, University of Victoria, Canada In this talk, I will present our works in the development of printable perovskite films with tens of nanometer thicknesses and their integration into photovoltaic modules. Time permitting, I will elaborate on our progress in the automated synthesis of perovskite single crystals with centimeter dimensions and their integration into X-ray detectors. |
16:25 |
Single-Crystal Plasmonics for Energy Harvesting and Catalysis
Albert Adserias, Simon Fraser University, Canada Finlay MacNab, Simon Fraser University, Canada Sasan Vosoogh-Grayli, University of Waterloo, Canada * Gary Leach, Simon Fraser University, Canada We describe a new platform chemistry to fabricate single crystal, plasmonic metal films and nanostructures with application to energy harvesting and catalysis. Surface plasmons concentrate the extended three-dimensional fields of propagating electromagnetic waves to nanometer-scale structures, where their enhanced and confined local fields can drive novel chemical and physical processes, including hot carrier generation, which can be leveraged for direct energy harvesting and catalysis applications. We identify the requirements for efficient hot electron extraction and demonstrate how this chemistry can be employed for the development of new green energy applications. |
16:40 |
Effect of in situ Exfoliation on the Photoluminescence and Photocatalytic Activity of Carbon Nitride
* Narendra Chaulagain, University of Alberta, Canada John Garcia, University of Alberta Kazi Alam, University of Alberta Karthik Shankar, University of Alberta Herein, carbon nitride nanosheets (CNNS) were synthesized using the in situ exfoliation technique by introducing sodiated sulfate hydrolyzed cellulose nanocrystals (NaCNC) in the precursor mixture. Na-CNNS exhibits strongly blue-shifted absorption and fluorescence edges, and significant advantages in photogenerated charge carrier transfer and separation when compared to bulk CN (BCN). Given its higher PEC water splitting performance, the Na-CNNS structure appears to be a suitable candidate for photocatalytic application. |
16:55 |
Etching-free pixel definition in InGaN green micro-LEDs
* Zhiyuan Liu, King Abdullah University of Science and Technology, Saudi Arabia Yi Lu, King Abdullah University of Science and Technology, Saudi Arabia Haicheng Cao, King Abdullah University of Science and Technology, Saudi Arabia Glen Isaac Maciel Garcia, King Abdullah University of Science and Technology, Saudi Arabia Tingang Liu, King Abdullah University of Science and Technology, Saudi Arabia Xiao Tang, King Abdullah University of Science and Technology, Saudi Arabia Na Xiao, King Abdullah University of Science and Technology, Saudi Arabia Raul Aguileta Vazquez, King Abdullah University of Science and Technology, Saudi Arabia Mingtao Nong, King Abdullah University of Science and Technology, Saudi Arabia Xiaohang Li, King Abdullah University of Science and Technology, Saudi Arabia The traditional plasma etching process for defining micro-LED pixels could lead to significant sidewall damage. Defects near sidewall regions act as non-radiative recombination centers and paths for current leakage, significantly deteriorating device performance. In this study, we demonstrated a novel selective thermal oxidation (STO) method that allowed pixel definition without undergoing plasma damage. The 10-µm green micro-LED array fabricated exhibited leakage currents density 1.2×10−6 A/cm² at −10 V and a peak on-wafer external quantum efficiency of approximately 6.55%. |