I-017

Paweł J. Kulesza

pkulesza@chem.uw.edu.pl

Anna Chmielnicka, Beata Rytelewska, Aldona Kostuch, Iwona A. Rutkowska

Faculty of Chemistry, University of Warsaw, Poland

Catalytic approaches for electrochemical reduction of inert inorganic molecules: oxygen, carbon dioxide and nitrogen

There has been growing interest in environmentally friendly alternative energy sources, energy conversion, and low-temperature methods of formation of fuels or utility chemicals. In this respect, the development of catalysts for effective electroreduction of small inert inorganic molecules, such as O2, CO2, and N2, is of primary importance. 

With reference to hydrogen-oxygen fuel cells, special attention has been paid to the development of both noble-metal-free and low-platinum-content electrocatalytic materials for efficient oxygen reduction with the ultimate goal of lowering the formation of undesirable H2O2 intermediate. An important strategy addressed here is the hybridization, activation, and stabilization of carbon-supported low-content Pt-catalysts by functionalization with certain nanostructured or substoichiometric metal oxides (e.g., CeO2 or WO3) both in simple or mixed forms.

Regarding the continuously rising levels of atmospheric carbon dioxide, the development of advanced technologies permitting CO2 utilization (reduction) is highly desirable. In principle, conventional electrocatalytic and visible-light-induced photoelectrochemical approaches are well-suited for reducing carbon dioxide and, possibly, generating carbon-based fuels or chemicals. But electroreduction of CO2 requires large over-potentials and suffers from the competitive hydrogen evolution. To overcome the problems, highly specific and selective catalysts would be required to drive effective conversion (reduction) of carbon dioxide (and water) into fuels, syn-gas, or utility chemicals. For example, the Cu-intercalated WO3 nanowires have exhibited good selectivity toward CO2-reduction, relative to the competitive hydrogen evolution, even in acidic medium.

The formation of ammonia is one of the most important chemical synthetic processes. In this respect, development of a low-temperature synthetic methodology is tempting from both practical and fundamental reasons. Currently, most electrochemical approaches to drive N2-fixation suffer from slow kinetics due to the difficulty of achieving the appropriate adsorption and activation of the dinitrogen molecule, leading to cleavage of the strong triple N≡N bond. We demonstrate that coordinatively stabilized iron catalytic sites, e.g., iron-centered heme-type porphyrins or iron phosphides, Fe2P or Fe3P, (alone or metal oxide supported)  could act as efficient catalysts for the formation of NH3 in alkaline and semi-neutral media.