1 High-pressure study of pyridine-mediated electrochemical reduction of CO 2 to methanol at a platinum electrode S. I. Rybchenko, D. Touhami, J. D. Wadhawan, S. K. Haywood. School of Engineering, University of Hull, Cottingham Road, Hull, HU6 7RX, UK Abstract The recently proposed highly efficient route of pyridine-catalysed CO2 reduction to methanol was explored on platinum electrodes at high CO2 pressure. At 55 bars of CO2, the bulk electrolysis in both potentiostatic and galvanostatic regimes resulted in methanol production with Faradaic yield up to 10% for the first 5-10 C/cm 2 of charge passed. For longer electrolysis, the methanol concentration failed to increase proportionally, being 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, even at excess CO2 concentration in the electrolyte. No prominent contribution from either a direct or coupled CO2 reduction was found. The results obtained suggest that the CO2 to methanol reduction is a transient process that is largely decoupled from the electrode charge transfer. This is the peer reviewed version of the following article: S. I. Rybchenko, D. Touhami, J. D. Wadhawan, S. K. Haywood, ChemSusChem 2016, 9, 1660, which has been published in final form at http://dx.doi.org/10.1002/ cssc.201600267. This article may be used for non-commercial purposes in accordance With Wiley Terms and Conditions for self-archiving.