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

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

Low pressure CO2 hydrogenation to methanol over gold nanoparticles activated on a CeOx/TiO2 Interface

Capture and recycling of CO2 into valuable chemicals such as alcohols could help mitigate its emissions into the atmosphere. Due to its inert nature, the activation of CO2 is a critical step in improving the overall reaction kinetics during its chemical conversion. Although pure gold is an inert noble metal and cannot catalyze hydrogenation reactions, it can be activated when deposited as nanoparticles on the appropriate oxide support. In this combined experimental and theoretical study, it is shown that an electronic polarization at the metal-oxide interface of Au nanoparticles anchored and stabilized on a CeOx/TiO2 substrate generates active centers for CO2 adsorption and its low pressure hydrogenation, leading to a higher selectivity toward methanol. This study illustrates the importance of localized electronic properties and structure in catalysis for achieving higher alcohol selectivity from CO2 hydrogenation.U.S. Department of Energy DE-AC02- 98CH10886, DE-AC02-05CH11231Brookhaven National Laboratory DE-SC001270

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

Effectively increased efficiency for electroreduction of carbon monoxide using supported polycrystalline copper powder electrocatalysts

Many electrocatalysts can efficiently convert CO_2 to CO. However, the further conversion of CO to higher-value products was hindered by the low activity of the CO reduction reaction and the consequent lack of mechanistic insights for designing better catalysts. A flow-type reactor could potentially improve the reaction rate of CO reduction. However, the currently available configurations would pose great challenges in reaction mechanism understanding due to their complex nature and/or lack of precise potential control. Here we report, in a standard electrochemical cell with a three-electrode setup, a supported bulk polycrystalline copper powder electrode reduces CO to hydrocarbons and multicarbon oxygenates with dramatically increased activities of more than 100 mA cm^(–2) and selectivities of more than 80%. The high activity and selectivity that was achieved demonstrates the practical feasibility of electrochemical CO or CO_2 (with a tandem strategy) conversion and enables the experimental exploration of the CO reduction mechanism to further reduced products

Effectively increased efficiency for electroreduction of carbon monoxide using supported polycrystalline copper powder electrocatalysts

Many electrocatalysts can efficiently convert CO_2 to CO. However, the further conversion of CO to higher-value products was hindered by the low activity of the CO reduction reaction and the consequent lack of mechanistic insights for designing better catalysts. A flow-type reactor could potentially improve the reaction rate of CO reduction. However, the currently available configurations would pose great challenges in reaction mechanism understanding due to their complex nature and/or lack of precise potential control. Here we report, in a standard electrochemical cell with a three-electrode setup, a supported bulk polycrystalline copper powder electrode reduces CO to hydrocarbons and multicarbon oxygenates with dramatically increased activities of more than 100 mA cm^(–2) and selectivities of more than 80%. The high activity and selectivity that was achieved demonstrates the practical feasibility of electrochemical CO or CO_2 (with a tandem strategy) conversion and enables the experimental exploration of the CO reduction mechanism to further reduced products