Andrew A. Gewirth

Bio: Andrew A. Gewirth is an academic researcher from University of Illinois at Urbana–Champaign. The author has contributed to research in topics: Electrolyte & Catalysis. The author has an hindex of 61, co-authored 298 publications receiving 13293 citations. Previous affiliations of Andrew A. Gewirth include University of Texas at Austin & Urbana University.

Electroreduction of dioxygen for fuel-cell applications: materials and challenges.

Abstract: A review of the oxygen reduction reaction (ORR) and its use in fuel-cell applications is presented. Discussed are mechanisms of the ORR and implementations of catalysts for this reaction. Specific catalysts discussed include nanoparticles, macrocycles and pyrolysis products, carbons, chalcogenides, enzymes, and coordination complexes. A prospectus for future efforts is provided.

Nonprecious Metal Catalysts for Oxygen Reduction in Heterogeneous Aqueous Systems

Abstract: A comprehensive review of recent advances in the field of oxygen reduction electrocatalysis utilizing nonprecious metal (NPM) catalysts is presented Progress in the synthesis and characterization of pyrolyzed catalysts, based primarily on the transition metals Fe and Co with sources of N and C, is summarized Several synthetic strategies to improve the catalytic activity for the oxygen reduction reaction (ORR) are highlighted Recent work to explain the active-site structures and the ORR mechanism on pyrolyzed NPM catalysts is discussed Additionally, the recent application of Cu-based catalysts for the ORR is reviewed Suggestions and direction for future research to develop and understand NPM catalysts with enhanced ORR activity are provided

Nanoporous Copper–Silver Alloys by Additive-Controlled Electrodeposition for the Selective Electroreduction of CO2 to Ethylene and Ethanol

Abstract: Electrodeposition of CuAg alloy films from plating baths containing 3,5-diamino-1,2,4-triazole (DAT) as an inhibitor yields high surface area catalysts for the active and selective electroreduction of CO2 to multicarbon hydrocarbons and oxygenates. EXAFS shows the co-deposited alloy film to be homogeneously mixed. The alloy film containing 6% Ag exhibits the best CO2 electroreduction performance, with the Faradaic efficiency for C2H4 and C2H5OH production reaching nearly 60 and 25%, respectively, at a cathode potential of just −0.7 V vs RHE and a total current density of ∼ – 300 mA/cm2. Such high levels of selectivity at high activity and low applied potential are the highest reported to date. In situ Raman and electroanalysis studies suggest the origin of the high selectivity toward C2 products to be a combined effect of the enhanced stabilization of the Cu2O overlayer and the optimal availability of the CO intermediate due to the Ag incorporated in the alloy.

Atomic-Resolution Electrochemistry with the Atomic Force Microscope: Copper Deposition on Gold

Abstract: The atomic force microscope (AFM) was used to image an electrode surface at atomic resolution while the electrode was under potential control in a fluid electrolyte. A new level of subtlety was observed for each step of a complete electrochemical cycle that started with an Au(111) surface onto which bulk Cu was electrodeposited. The Cu was stripped down to an underpotential-deposited monolayer and finally returned to a bare Au(111) surface. The images revealed that the underpotential-deposited monolayer has different structures in different electrolytes. Specifically, for a perchloric acid electrolyte the Cu atoms are in a close-packed lattice with a spacing of 0.29 ± 0.02 nanometer (nm). For a sulfate electrolyte they are in a more open lattice with a spacing of 0.49 ± 0.02 nm. As the deposited Cu layer grew thicker, the Cu atoms converged to a (111)-oriented layer with a lattice spacing of 0.26 ± 0.02 nm for both electrolytes. A terrace pattern was observed during dissolution of bulk Cu. Images were obtained of an atomically resolved Cu monolayer in one region and an atomically resolved Au substrate in another in which a 30° rotation of the Cu monolayer lattice from the Au lattice is clearly visible.

Fast parallel algorithms for short-range molecular dynamics

Abstract: Three parallel algorithms for classical molecular dynamics are presented. The first assigns each processor a fixed subset of atoms; the second assigns each a fixed subset of inter-atomic forces to compute; the third assigns each a fixed spatial region. The algorithms are suitable for molecular dynamics models which can be difficult to parallelize efficiently—those with short-range forces where the neighbors of each atom change rapidly. They can be implemented on any distributed-memory parallel machine which allows for message-passing of data between independently executing processors. The algorithms are tested on a standard Lennard-Jones benchmark problem for system sizes ranging from 500 to 100,000,000 atoms on several parallel supercomputers--the nCUBE 2, Intel iPSC/860 and Paragon, and Cray T3D. Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems. For large problems, the spatial algorithm achieves parallel efficiencies of 90% and a 1840-node Intel Paragon performs up to 165 faster than a single Cray C9O processor. Trade-offs between the three algorithms and guidelines for adapting them to more complex molecular dynamics simulations are also discussed.

Co3O4 nanocrystals on graphene as a synergistic catalyst for oxygen reduction reaction

Abstract: Catalysts for oxygen reduction and evolution reactions are at the heart of key renewable-energy technologies including fuel cells and water splitting. Despite tremendous efforts, developing oxygen electrode catalysts with high activity at low cost remains a great challenge. Here, we report a hybrid material consisting of Co₃O₄ nanocrystals grown on reduced graphene oxide as a high-performance bi-functional catalyst for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Although Co₃O₄ or graphene oxide alone has little catalytic activity, their hybrid exhibits an unexpected, surprisingly high ORR activity that is further enhanced by nitrogen doping of graphene. The Co₃O₄/N-doped graphene hybrid exhibits similar catalytic activity but superior stability to Pt in alkaline solutions. The same hybrid is also highly active for OER, making it a high-performance non-precious metal-based bi-catalyst for both ORR and OER. The unusual catalytic activity arises from synergetic chemical coupling effects between Co₃O₄ and graphene.

Reviving the lithium metal anode for high-energy batteries

Abstract: Lithium-ion batteries have had a profound impact on our daily life, but inherent limitations make it difficult for Li-ion chemistries to meet the growing demands for portable electronics, electric vehicles and grid-scale energy storage. Therefore, chemistries beyond Li-ion are currently being investigated and need to be made viable for commercial applications. The use of metallic Li is one of the most favoured choices for next-generation Li batteries, especially Li-S and Li-air systems. After falling into oblivion for several decades because of safety concerns, metallic Li is now ready for a revival, thanks to the development of investigative tools and nanotechnology-based solutions. In this Review, we first summarize the current understanding on Li anodes, then highlight the recent key progress in materials design and advanced characterization techniques, and finally discuss the opportunities and possible directions for future development of Li anodes in applications.

Multicopper Oxidases and Oxygenases

Abstract: Copper is an essential trace element in living systems, present in the parts per million concentration range. It is a key cofactor in a diverse array of biological oxidation-reduction reactions. These involve either outer-sphere electron transfer, as in the blue copper proteins and the Cu{sub A} site of cytochrome oxidase and nitrous oxide redutase, or inner-sphere electron transfer in the binding, activation, and reduction of dioxygen, superoxide, nitrite, and nitrous oxide. Copper sites have historically been divided into three classes based on their spectroscopic features, which reflect the geometric and electronic structure of the active site: type 1 (T1) or blue copper, type 2 (T2) or normal copper, and type 3 (T3) or coupled binuclear copper centers. 428 refs.