Two major energy-related problems confront the world in the
next 50 years. First, increased worldwide competition for
gradually depleting fossil fuel reserves (derived from past
photosynthesis) will lead to higher costs, both monetarily and politically. Second, atmospheric CO_2 levels are at their highest recorded level since records began. Further increases are predicted to produce large and uncontrollable impacts on the world climate. These projected impacts extend beyond climate to ocean acidification, because the ocean is a major sink for atmospheric CO2.1 Providing a future energy supply that is secure and CO_2-neutral will require switching to nonfossil energy sources such as wind, solar, nuclear, and geothermal energy and developing methods for transforming the energy produced by these new sources into forms that can be stored, transported, and used upon demand.

Frontiers, Opportunities, and Challenges in Biochemical and Chemical Catalysis of CO2 Fixation

Catalytic removal of NO

This review summarizes different catalytic options for the production of syngas and hydrogen starting from simple hydrogen-containing molecules. Particular attention is given to new direct catalytic alternatives in natural gas conversion. Improvements in syngas technology are discussed, including partial oxidation, autothermal reforming, combined reforming and carbon dioxide reforming, and the energy efficiencies of direct and indirect methane conversion are compared. Processes, issues and practical difficulties are discussed with academic and applied efforts presented in parallel. It is emphasized that most of the ongoing research related to the direct processes is at the exploratory stage while technology utilizing indirect approach has advanced to semi-works and initial commercialization plants. The new emerging processes based on partial oxidation features are unique for syngas generation. Further enhancement of such processes plus improvements in other second generation technologies and advances in direct processes are anticipated to provide additional, new attractive paths to the chemical conversion of natural gas. Similarly, on board generation of hydrogen-rich gaseous fuels either for spark ignition engines or for coupled-fuel-cells electric engines is discussed within the scope of both partial oxidation and catalytic decomposition of methanol. A concept based in the thermochemical water splitting, which provides a renewable portable fuel from water in the form of H2, is also presented. Above all, as the chemistry involved in most of these catalytic alternatives takes place under extreme conditions, highly stable catalysts and engineering concepts are being developed.

New catalytic routes for syngas and hydrogen production

CO electroreduction activity on oxide-derived Cu (OD-Cu) was found to correlate with metastable surface features that bind CO strongly. OD-Cu electrodes prepared by H2 reduction of Cu2O precursors reduce CO to acetate and ethanol with nearly 50% Faradaic efficiency at moderate overpotential. Temperature-programmed desorption of CO on OD-Cu revealed the presence of surface sites with strong CO binding that are distinct from the terraces and stepped sites found on polycrystalline Cu foil. After annealing at 350 °C, the surface-area corrected current density for CO reduction is 44-fold lower and the Faradaic efficiency is less than 5%. These changes are accompanied by a reduction in the proportion of strong CO binding sites. We propose that the active sites for CO reduction on OD-Cu surfaces are strong CO binding sites that are supported by grain boundaries. Uncovering these sites is a first step toward understanding the surface chemistry necessary for efficient CO electroreduction.

M. J. Sandoval

Papers

Infrared Studies of the Mechanism of Methanol Decomposition on Cu/SiO2

Temperature-Programmed Desorption Studies of the Interactions of H2, CO, and CO2 with Cu/SiO2