Title:	Mechanistic understanding of molecular catalysts for water oxidation and carbon dioxide reduction-important step in developing non-fossil fuels
DNr:	SNIC 2016/1-174
Project Type:	SNIC Medium Compute
Principal Investigator:	Sascha Ott <sascha.ott@kemi.uu.se>
Affiliation:	Uppsala universitet
Duration:	2016-04-01 – 2017-04-01
Classification:	10404 10405
Homepage:	http://www.kemi.uu.se/Research/principal-investigators/sascha-ott/
Keywords:

Abstract

To design active catalysts, understanding of the catalytic pathway and the structure of reactive intermediates are of prime importance. This project emphasizes on understanding a) Electrocatalytic carbon dioxide reduction using Ruthenium catalysts b) Photo-induced catalytic water oxidation pathways using Iron and Cobalt catalysts and possible structures of the reactive intermediates. a) CO2 reduction serves as one of the renewable carbon-neutral sources to produce low-carbon products. CO is one of the components of water gas which is presently combined with gasification of coal to produce pure hydrogen. HCOOH is one of the most promising materials for hydrogen storage today since it readily decomposes into H2 and CO2 in the presence of a suitable catalyst. CH3OH has an advantage of being a liquid. Methane is more easily stored than hydrogen. Thus CO2 reduction can also be readily employed on commercial scale to meet the urgent requirements of alternative renewable sources of energy. Designing catalysts for CO2 reduction is still in its preliminary stage and is a blooming area of research. As stated above, to build efficient catalysts, the understanding of mechanistic details (energies and nature of transition states and intermediates) is very important and for that computational tools are essential. Some of the ruthenium complexes synthesized by our group have been studied recently and using DFT, we have been able to understand the fact that the first electron entering the ligand fortified the reduction of CO2 bound to the metal center. b) Solar energy induced water splitting process requires the coupling of the two half-reactions: (i) oxidation of H2O to generate the reducing equivalents and (ii) reduction of protons to molecular hydrogen. As water oxidation is the bottle neck of this process, development of water oxidation catalysts (WOC) have been exhilarated. Quite many Ruthenium and Iridium complexes have been reported till date to be active in this catalytic process and can be useful in understanding the catalytic pathways which are pivotal developing better catalysts; but extensive use of such metals brings some of the obstacles such as being expensive and toxic. To be able to use widely, we need to concentrate on earth abundant, cheap first row transition metals which can sustain multiple redox levels. Fulfilling the above mentioned criteria, Iron and Cobalt complexes exemplify a prospective candidate. Although few iron and cobalt complexes have been reported to catalyze water oxidation , the complete mechanism is yet to be revealed. In this quest we have been investigating robust Fe and Co polypyridyl complexes. As the catalytic water oxidation results are very promising, detail mechanistic investigations are being commenced to proceed towards developing improved catalysts. Recently we have been able to understand strong influence of the chloride ion in the catalytic water oxidation activity and complete mechanism involving high valent metal oxo species is under investigation. 1. BA. Johnson, S.Maji, H.Agarwala, TA White, E.Mijangos, and Sascha Ott Angew.Chem. 2016, 55, 1825–1829. 2. B.Das, A.Orthaber, Sascha Ott, and Anders Thapper accepted ChemSusChem