In operando studies on the electrochemical oxidation of water mediated by molecular catalysts

Catalysis and Surface Chemistr

Evaluation of iron-based electrocatalysts for water oxidation: an on-line mass spectrometry approach

Metals in Catalysis, Biomimetics & Inorganic MaterialsCatalysis and Surface Chemistr

Design principles for homogeneous water oxidation catalysts based on first–row transition metals

The development of homogeneous first-row transition metal (FRTM) catalysts for the water oxidation reaction is considerably more challenging than for second and third-row catalysts. Given that FRTM catalysts are, in general, more labile, additional design principles must be considered to develop robust and stable catalysts for the water oxidation reaction. In this review, we highlight important design criteria and summarize important lessons learned for FRTM water oxidation catalysts.Catalysis and Surface Chemistr

On the homogeneity of a cobalt-based water oxidation catalyst

The homogeneity of molecular Co-based wateroxidation catalysts (WOCs) has been a subject of debate over thelast 10 years as assumed various homogeneous Co-based WOCswere found to actually form CoOxunder operating conditions. Thehomogeneity of the Co(HL)(HL=N,N-bis(2,2 '-bipyrid-6-yl)amine) system was investigated with cyclic voltammetry,electrochemical quartz crystal microbalance, and X-ray photo-electron spectroscopy. The obtained experimental results werecompared with heterogeneous CoOx. Although it is shown thatCo(HL) interacts with the electrode during electrocatalysis, theformation of CoOxwas not observed. Instead, a molecular depositof Co(HL) was found to be formed on the electrode surface. Thisstudy shows that deposition of catalytic material is not necessarilylinked to the decomposition of homogeneous cobalt-based water oxidation catalysts.Catalysis and Surface Chemistr

Thermally induced Oxygen vacancies in BiOCl nanosheets and their impact on photoelectrochemical performance

Oxygen vacancies (OVs) have been reported to significantly alter the photocatalytic properties of BiOCl nanosheets. However, their formation mechanism and their role in the enhancement of photoelectrochemical performance remain unclear. In this work, thermally induced oxygen vacancies are introduced in BiOCl nanosheets by annealing in He atmosphere at various temperatures and their formation mechanism is investigated by in-situ diffuse reflectance infrared (DRIFTS) measurements. The influence of OVs on band offset, carrier concentrations and photoelectrochemical performance are systematically studied. The results show that (1) the surface of BiOCl nanosheets is extremely sensitive to temperature and defects are formed at temperatures as low as 200 degrees C in inert atmosphere. (2) The formation of surface and bulk OVs in BiOCl is identified by a combination of XPS, in-situ DRIFTS, and EPR experiments. (3) The photocurrent of BiOCl is limited by the concentration of charge carriers and shallow defect states induced by bulk oxygen vacancies, while the modulation of these parameters can effectively increase light absorption and carrier concentration leading to an enhancement of photoelectrochemical performance of BiOCl.Metals in Catalysis, Biomimetics & Inorganic Material

Electrochemical and Spectroscopic Study of Mononuclear Ruthenium Water Oxidation Catalysts: A Combined Experimental and Theoretical Investigation

Solid state NMR/Biophysical Organic Chemistr

Fast Oxygen Reduction Catalyzed by a Copper(II) Tris(2-pyridylmethyl)amine Complex through a Stepwise Mechanism

Catalytic pathways for the reduction of dioxygen can either lead to the formation of water or peroxide as the reaction product. We demonstrate that the electrocatalytic reduction of O2 by the pyridylalkylamine copper complex [Cu(tmpa)(L)]2+ in a neutral aqueous solution follows a stepwise 4 e−/4 H+ pathway, in which H2O2 is formed as a detectable intermediate and subsequently reduced to H2O in two separate catalytic reactions. These homogeneous catalytic reactions are shown to be first order in catalyst. Coordination of O2 to CuI was found to be the rate‐determining step in the formation of the peroxide intermediate. Furthermore, electrochemical studies of the reaction kinetics revealed a high turnover frequency of 1.5×105 s−1, the highest reported for any molecular copper catalyst.Metals in Catalysis, Biomimetics & Inorganic Material

Me2-NHC based robust Ir catalyst for efficient water oxidation

Me2-NHC proved to be a valuable ligand in iridium catalyzed water oxidation reactions, both when carried out electrochemically as well as upon oxidation with cerium ammonium nitrate. Mechanistic data suggest that water oxidation occurs efficiently at a well defined iridium species via a mononuclear pathway