Conference Programme

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E-04: Electrocatalyst II
Tuesday, 20/Jun/2017:
1:30pm - 3:30pm

Session Chair: Rong Xu, Nanyang Technological University
Session Chair: Shizhang Qiao, University of Adelaide
Location: Nicoll 1

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1:30pm - 2:00pm

Nanoscale Metal-Organic Frameworks: Emerging Materials for Catalysis

Zhiyong TANG

National Center of Nanoscience and Technology, China

Distinct from classic inorganic nanoparticles of solid cores, nanoscale metal-organic frameworks (NMOFs) are of ordered crystalline pores with tunable composite, size and volume, which provide an ideal platform not only to manipulate the reaction active sites but also to understand the structure-functionality relationship. In this presentation, we will introduce two recent works involving catalytic application of NMOFS.

2:00pm - 2:15pm

Graphene Quantum Dot Hybrids for the Enhanced Oxygen Reduction Reaction

Ki Hwan KOH, Kihyun LEE, Sung-Chul YI, Tae Hee HAN

Hanyang University, South Korea

Graphene quantum dots (GQDs) have been widely investigated due to the various advantages including easy synthesis procedures, non-toxicity, chemical/physical stability, and controllable chemical functionality. GQDs can be easily hybridized with other nanomaterials due to the presence of functional groups, which can provide good opportunities to make a new designed material for better electrocatalytic performance. In this work, GQDs were covalently functionalized with iron (II) phthalocyanine (FePC) by a facile ferric chloride reaction in order to improve the oxygen reduction reaction (ORR) performance. Electrochemical measurements showed that GQDs functionalized with FePC exhibited enhanced electrocatalytic activity, implying that GQD-FePC could be used as an alternative electrocatalyst to commercial Pt/C in fuel cells.

2:15pm - 2:30pm

Supportless Pt-Based Electrocatalysts for Oxygen Reduction Reaction

Bao Yu XIA

Huazhong University of Science and Technology, China

Designing effective electrocatalysts for fuel cells has been a key scientific objective due to the urgent need for practical, cost-effective and sustainable energy sources. The extensive commercial application has been heavily hindered by several technological challenges, such as the high cost, poor activity and performance degradation of Pt/carbon catalyst in the sluggish oxygen reduction reaction (ORR). To move towards the successful commercialization, emphasizing solely on the catalytic activity is not sufficient, and requirements on performance stability are also stringent. Here we offer our Perspective on the most exciting developments in the materials science of self-supported Pt-based electrocatalysts, with an emphasis on alternatives (1D motifs, 2D membrane and 3D superstructure) to the state-of-the-art carbon supported Pt catalyst. After overviewing recent developments, we highlight the challenges and opportunities of the self-supported Pt-based electrocatalysts, which may offer a broad materials library for fuel cells and energy conversion applications.

2:30pm - 2:45pm

Optimizing C-C Coupling on Oxide Derived Copper Catalysts for Electrochemical CO2 Reduction

Yanwei LUM1,2,3, Binbin YUE4,5, Peter LOBACCARO1,6,7, Alexis T. BELL1,6,7, Joel W. AGER1,2,3

1Joint Center for Artificial Photosynthesis, Lawrence Berkeley National Laboratory, United States; 2Department of Materials Science and Engineering, University of California, Berkeley, United States; 3Materials Sciences Division, Lawrence Berkeley National Laboratory, United States; 4Center for High Pressure Science and Technology Advanced Research, China; 5Advanced Light Source, Lawrence Berkeley National Laboratory, United States; 6Department of Chemical and Biomolecular Engineering, University of California, Berkeley, United States; 7Chemical Sciences Division, Lawrence Berkeley National Laboratory, United States

Recently, "oxide derived" copper catalysts have been extensively studied for electrochemical CO2 reduction. Their typical preparation process involves oxidizing metallic copper to form copper oxides which are then reduced back to their metallic state. Catalysts so prepared have been reported to have higher activity and better selectivity towards C2 and C3 (C2+) products compared to their original form. Herein, we systematically compare four different variations of these electrocatalysts (as reported by others in the literature) and show that changing the cation of the electrolyte can further enhance their selectivities and activities towards C2+ products. We utilize two electrolyte conditions, 0.1 M KHCO3 and 0.1 M CsHCO3, and find that the presence of the larger cation in the electrolyte yields increases in selectivity towards C2+ products from -0.7 V to -1.0 V vs RHE for all catalysts studied. On the best performing oxide-derived catalysts with Cs+, we observe up to ~70% selectivity towards C2+ products with only ~3% selectivity towards C1 products at -1.0 V vs RHE. At the same conditions with K+, only ~56% selectivity towards C2+ products was observed. Additionally, study of these different electrocatalysts under the same conditions, combined with in-depth characterization with techniques such as synchrotron x-ray diffraction and x-ray photoelectron spectroscopy, allows us to discern the key factors governing product selectivity. We find that morphology, grain size and surface roughness of the oxide derived layer are critical parameters which affect the catalytic performance. The grain size of an optimally performing catalyst should be small and the morphology has to be optimized so as to raise local pH and enhance selectivity to C2+ products but not result in CO2 mass transport limitations. Electrochemical transport models have also been developed to better instruct future morphological designs of such oxide derived catalysts.

2:45pm - 3:00pm

Improved CO2 Electroreduction Selectivity on Solution Grown Non-Metallic Copper Starting Phases

Albertus Denny HANDOKO1, Boon Siang YEO2

1Institute of Materials Research and Engineering, Agency for Science, Technology and Research (A*STAR), Singapore; 2National University of Singapore, Singapore

The reduction of carbon dioxide to hydrocarbons and alcohols has the potential of generating a sustainable supply of valuable feedstock for our chemical industries and fuels to meet our energy needs. Metallic Cu is one of the most commonly reported materials capable of reducing CO2 to various carbonaceous products photo or electrocatalytically. However, product selectivity, and robustness remain as major concerns for Cu electrocatalyst.

Higher carbon chain products are more appealing for the higher energy density they contain. Although bare metallic Cu is capable of reducing CO2 electrocatalytically to higher carbon-chain products like ethylene and ethanol and many others, the current selectivity is typically low and rapid poisoning of metallic Cu is often reported.

In this study, the effect of various copper starting phases such as copper oxides using low temperature solution growth methods on CO2 electroreduction are investigated. Although all different copper starting phases will eventually reduce to metallic Cu at the electrochemical CO2 reduction potential, it was found that different copper starting phase improved the selectivity towards certain higher carbon-chain products like C2H4 or ethanol. Additionally, H2 selectivity can be suppressed down to 20% using non-metallic copper starting phase. Apart from the known voltage dependant product distribution, it was found that particle size, microstrains and crystallite faceting strongly favour the production of higher carbon chain products.

Interestingly, these solution grown non-metallic Cu starting phases were also found to be much more stable than bare metallic Cu. >6 hours of CO2 electroreduction could be performed with minimal current decay as compared to metallic Cu. These selectivity and stability phenomena could not be replicated by nanoparticulate Cu deposition (via electrodeposition), highlighting the importance of the freshly reduced Cu surfaces in CO2 electroreduction.

3:00pm - 3:30pm

Photoelectrochemical Solar Water Splitting from Disordered Metal Oxide Semiconductors

Jong Hyeok PARK

Yonsei University, South Korea

The development of new types of energy generation devices is promoted by increasing public awareness that the Earth's oil reserves could run out during this century. As the energy needs of the planet are likely to double within the next 50 years, the stage is set for a major energy shortage, unless renewable energy can cover the substantial deficit left by fossil fuels. Photoelectrochemical (PEC) solar water splitting has become a central research theme for more than four decades, still, their efficiencies remain low. Despite extensive efforts devoted to modifying photoelectrodes through various bandgap and catalysis engineering, the efficient methodologies for charge transfer at electrode/electrolyte interface remain underdeveloped. In this seminar, I will introduce various unique methods to increase light harvesting efficiency to generate hydrogen from solar light by applying disordered engineering to metal oxide materials. Especially, high efficiency TiO2, WO3, and BiVO4 photoanodes with the modification and charge transfer across the electrode/electrolyte interface will be presented.

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