Study of pyridine-mediated electrochemical reduction of CO2 to methanol at high CO2 pressure

© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim The recently proposed highly efficient route of pyridine-catalyzed CO 2 reduction to methanol was explored on platinum electrodes at high CO 2 pressure. At 55 bar (5.5 MPa) of CO 2 , the bulk electrolysis in both potentiostatic and galvanostatic regimes resulted in methanol production with Faradaic yields of up to 10 % for the first 5–10 C cm −2 of charge passed. For longer electrolysis, the methanol concentration failed to increase proportionally and was limited to sub-ppm levels irrespective of biasing conditions and pyridine concentration. This limitation cannot be removed by electrode reactivation and/or pre-electrolysis and appears to be an inherent feature of the reduction process. In agreement with bulk electrolysis findings, the CV analysis supported by simulation indicated that hydrogen evolution is still the dominant electrode reaction in pyridine-containing electrolyte solution, even with an excess CO 2 concentration in the solution. No prominent contribution from either a direct or coupled CO 2 reduction was found. The results obtained suggest that the reduction of CO 2 to methanol is a transient process that is largely decoupled from the electrode charge transfer

Photoactivatable Platinum(IV) Pro-Drugs as Novel Delivery Vehicles for Chemotherapeutics. Part II: Pyridinium-Catalyzed Photoelectrochemical Reduction of CO2 to Multi-Carbon Products on p-Gallium Arsenide

This thesis is divided into two parts. The first part of this thesis describes the photochemistry and cytotoxicity of six platinum(IV) trinuclear charge transfer pro-drugs. These complexes are reduced to the potent platinum(II) chemotherapeutics cisplatin, carboplatin, or oxaliplatin upon absorption of visible light, which results in a two electron transfer. Platinum(IV) photoactivatable pro-drugs have several advantages over platinum(II) drugs. Primarily, they are useful for targeted, localized treatment of tumors in combination with high-energy light sources. Treatments of this nature increase the therapeutic ratio, allowing for higher doses to be administered to patients, since the active drug is not disseminated to healthy tissues. Evidence for the reformation of the parent platinum(II) complex was obtained by incubation of the trinuclear pro-drugs with plasmid DNA. Irradiation of the mixture resulted in a shift of the migration of the plasmid through agarose during electrophoresis, indicating platinum was binding to the helix. Accumulation and cytotoxicity of the complexes was determined with A549 and MCF-7 cancer cell lines. The second part extends the study of CO2 reduction to a p-GaAs electrode in the presence of the pyridinum electrocatalyst. Modification of the p-GaAs electrode surface with a discontinuous platinum layer minimized photocorrosion. Multi-carbon products were observed such as 2-propanol and acetone, with Faradaic yields of 56% and 36% respectively. Electrolysis in a closed system altered the product distribution with the primary products becoming 2-butanol and methanol. Mass spectral analysis of bulk electrolysis run with 13C labeled CO2 confirmed the observed products were in fact reduced from CO2

<span style="font-size:11.0pt;font-family: "Times New Roman";mso-fareast-font-family:"Times New Roman";mso-bidi-font-family: Mangal;mso-ansi-language:EN-GB;mso-fareast-language:EN-US;mso-bidi-language: HI" lang="EN-GB">Analysis of pyridinium catalyzed electrochemical and photoelectrochemical reduction of CO₂: Chemistry and economic impact</span>

1284-1297This review highlights the recent work related to the electrochemical and photoelectrochemical conversion of carbon dioxide into methanol and formic acid. Information related to the structural, mechanistic and kinetic aspects of the pyridinium and imidazolium catalyzed reduction processes is presented. The economic impact of these processes is delineated by calculating the cost per billion gallons of gasoline equivalence for methanol by three methods viz., electrochemical conversion, photoelectrochemical conversion, combined electrochemical conversion and thermal conversion. Our initial analysis shows that the last method may be the most economically feasible method under the existing technologies