Fuel Cell Research at the University of Delaware

The grant initiated nine basic and applied research projects to improve fundamental understanding and performance of the proton exchange membrane (PEM) fuel cells, to explore innovative methods for hydrogen production and storage, and to address the critical issues and barriers to commercialization. The focus was on catalysis, hydrogen production and storage, membrane durability and flow modeling and characterization of Gas Diffusion Media. Three different types of equipment were purchase with this grant to provide testing and characterization infrastructure for fuel cell research and to provide undergraduate and graduate students with the opportunity to study fuel cell membrane design and operation. They are (i) Arbin Hydrogen cell testing station, (ii) MTS AllianceâÃÂâ RT/5 material testing system with an ESPEC custom-designed environmental chamber for membrane Durability Testing and (iii) Chemisorption for surface area measurements of electrocatalysts. The research team included ten faculty members who addressed various issues that pertain to Fuel Cells, Hydrogen Production and Storage, Fuel Cell transport mechanisms. Nine research tasks were conducted to address the critical issues and various barriers to commercialization of Fuel Cells. These research tasks are subdivided in the general areas of (i) Alternative electrocatalysis (ii) Fuel Processing and Hydrogen Storage and (iii) Modeling and Characterization of Membranes as applied to Fuel Cells research.. The summary of accomplishments and approaches for each of the tasks is presented belo

Promoting H2O2 production via 2-electron oxygen reduction by coordinating partially oxidized Pd with defect carbon.

Electrochemical synthesis of H2O2 through a selective two-electron (2e-) oxygen reduction reaction (ORR) is an attractive alternative to the industrial anthraquinone oxidation method, as it allows decentralized H2O2 production. Herein, we report that the synergistic interaction between partially oxidized palladium (Pdδ+) and oxygen-functionalized carbon can promote 2e- ORR in acidic electrolytes. An electrocatalyst synthesized by solution deposition of amorphous Pdδ+ clusters (Pd3δ+ and Pd4δ+) onto mildly oxidized carbon nanotubes (Pdδ+-OCNT) shows nearly 100% selectivity toward H2O2 and a positive shift of ORR onset potential by ~320 mV compared with the OCNT substrate. A high mass activity (1.946 A mg-1 at 0.45 V) of Pdδ+-OCNT is achieved. Extended X-ray absorption fine structure characterization and density functional theory calculations suggest that the interaction between Pd clusters and the nearby oxygen-containing functional groups is key for the high selectivity and activity for 2e- ORR

OsNAR2.1 Positively Regulates Drought Tolerance and Grain Yield Under Drought Stress Conditions in Rice

Drought is an important environmental factor that severely restricts crop production. The high-affinity nitrate transporter partner protein OsNAR2.1 plays an essential role in nitrate absorption and translocation in rice. Our results suggest that OsNAR2.1 expression is markedly induced by water deficit. After drought stress conditions and irrigation, compared with wild-type (WT), the survival rate was significantly improved in OsNAR2.1 over-expression lines and decreased in OsNAR2.1 RNAi lines. The survival rate of Wuyunjing7 (WYJ), OsNRT2.1 over-expression lines and OsNRT2.3a over-expression lines was not significantly different. Compared with WT, overexpression of OsNAR2.1 could significantly increase nitrogen uptake in rice, and OsNAR2.1 RNAi could significantly reduce nitrogen uptake. Under drought conditions, the expression of OsNAC10, OsSNAC1, OsDREB2a, and OsAP37 was significantly reduced in OsNAR2.1 RNAi lines and increased substantially in OsNAR2.1 over-expression lines. Also, the chlorophyll content, relative water content, photosynthetic rate and water use efficiency were decreased considerably in OsNAR2.1 RNAi lines and increased significantly in OsNAR2.1 over-expression lines under drought conditions. Finally, compared to WT, grain yield increased by about 9.1 and 26.6%, in OsNAR2.1 over-expression lines under full and limited irrigation conditions, respectively. These results indicate that OsNAR2.1 regulates the response to drought stress in rice and increases drought tolerance

Imaging with an ultra-thin reciprocal lens

Imaging is of great importance in everyday life and various fields of science and technology. Conventional imaging is achieved by bending light rays originating from an object with a lens. Such ray bending requires space-variant structures, inevitably introducing a geometric center to the lens. To overcome the limitations arising from the conventional imaging mechanism, we consider imaging elements that employ a different mechanism, which we call reciprocal lenses. This type of imaging element relies on ray shifting, enabled by momentum-space-variant phase modulations in periodic structures. As such, it has the distinct advantage of not requiring alignment with a geometric center. Moreover, upright real images can be produced directly with a single reciprocal lens as the directions of rays are not changed. We realized an ultra-thin reciprocal lens based on a photonic crystal slab. We characterized the ray shifting behavior of the reciprocal lens and demonstrated imaging. Our work gives an alternative mechanism for imaging, and provides a new way to modulate electromagnetic waves

Computational and experimental demonstrations of one-pot tandem catalysis for electrochemical carbon dioxide reduction to methane

Electroreduction of carbon dioxide to hydrocarbons and oxygenates on copper involves reduction to a carbon monoxide adsorbate followed by further transformation to hydrocarbons and oxygenates. Simultaneous improvement of these processes over a single reactive site is challenging due to the linear scaling relationship of the binding strength of key intermediates. Herein, we report improved electroreduction of carbon dioxide by exploiting a one-pot tandem catalysis mechanism based on computational and electrochemical investigations. By constructing a well-defined copper-modified silver surface, adsorbed carbon monoxide generated on the silver sites is proposed to migrate to surface copper sites for the subsequent reduction to methane, which is consistent with insights gained from operando attenuated total reflectance surface enhanced infrared absorption spectroscopic investigations. Our results provide a promising approach for designing carbon dioxide electroreduction catalysts to enable one-pot reduction of products beyond carbon monoxide and formate

Oxygen induced promotion of electrochemical reduction of CO₂ via co-electrolysis

Harnessing renewable electricity to drive the electrochemical reduction of CO₂ is being intensely studied for sustainable fuel production and as a means for energy storage. Copper is the only monometallic electrocatalyst capable of converting CO₂ to value-added products, e.g., hydrocarbons and oxygenates, but suffers from poor selectivity and mediocre activity. Multiple oxidative treatments have shown improvements in the performance of copper catalysts. However, the fundamental underpinning for such enhancement remains controversial. Here, we combine reactivity, in-situ surface-enhanced Raman spectroscopy, and computational investigations to demonstrate that the presence of surface hydroxyl species by co-electrolysis of CO₂ with low concentrations of O₂ can dramatically enhance the activity of copper catalyzed CO2 electroreduction. Our results indicate that co-electrolysis of CO₂ with an oxidant is a promising strategy to introduce catalytically active species in electrocatalysis

Oxygen induced promotion of electrochemical reduction of CO₂ via co-electrolysis

Harnessing renewable electricity to drive the electrochemical reduction of CO₂ is being intensely studied for sustainable fuel production and as a means for energy storage. Copper is the only monometallic electrocatalyst capable of converting CO₂ to value-added products, e.g., hydrocarbons and oxygenates, but suffers from poor selectivity and mediocre activity. Multiple oxidative treatments have shown improvements in the performance of copper catalysts. However, the fundamental underpinning for such enhancement remains controversial. Here, we combine reactivity, in-situ surface-enhanced Raman spectroscopy, and computational investigations to demonstrate that the presence of surface hydroxyl species by co-electrolysis of CO₂ with low concentrations of O₂ can dramatically enhance the activity of copper catalyzed CO2 electroreduction. Our results indicate that co-electrolysis of CO₂ with an oxidant is a promising strategy to introduce catalytically active species in electrocatalysis