Selective electrooxidation of 2-propanol on Pt nanoparticles supported on Co₃O₄: an in-situ study on atomically defined model systems

Abstract

2-Propanol and its dehydrogenated counterpart acetone can be used as a rechargeable electrofuel. The concept involves selective oxidation of 2-propanol to acetone in a fuel cell coupled with reverse catalytic hydrogenation of acetone to 2-propanol in a closed cycle. We studied electrocatalytic oxidation of 2-propanol on complex model Pt/Co3O4(111) electrocatalysts prepared in ultra-high vacuum and characterized by scanning tunneling microscopy. The electrocatalytic behavior of the model electrocatalysts has been investigated in alkaline media (pH 10, phosphate buffer) by means of electrochemical infrared reflection absorption spectroscopy and ex-situ emersion synchrotron radiation photoelectron spectroscopy as a function of Pt particle size and compared with the electrocatalytic behavior of Pt(111) and pristine Co3O4(111) electrodes under similar conditions. We found that the Co3O4(111) film is inactive towards electrochemical oxidation of 2-propanol under the electrochemical conditions (0.3–1.1 VRHE). The electrochemical oxidation of 2-propanol readily occurs on Pt(111) yielding acetone at an onset potential of 0.4 VRHE. The reaction pathway does not involve CO but yields strongly adsorbed acetone species leading to a partial poisoning of the surface sites. On model Pt/Co3O4(111) electrocatalysts, we observed distinct metal support interactions and particle size effects associated with the charge transfer at the metal/oxide interface. We found that ultra-small Pt particles (around 1 nm and below) consist of partially oxidized Pt δ + species which show minor activity towards 2-propanol oxidation. In contrast, conventional Pt particles (particle size of a few nm) are mainly metallic and show high activity toward 2-propanol oxidation.

Highly Selective TEMPO Catalyzed Bulk Electrooxidation of Isopropanol to Acetone for Application in Electrochemical Heat Pumping

“…Apart from the ELHP, an IPA-acetone fluid pair is also of interest to the fuel cell community, as efficient interconversion of these species is required for the proper functioning of IPA based fuel cells. , Several catalysts that facilitate the oxidation of alcohols to their corresponding carbonyl products have been reported in the literature. , However, most of them require precise temperature, pressure control, and/or the use of expensive bimetallic catalysts. ,− Stable organic nitroxyl radicals, particularly 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO), have emerged as environmentally benign molecular catalysts for the efficient oxidation of alcohols. − In addition, TEMPO and its derivatives are promising catholytes for use in aqueous redox-flow batteries due to their high solubility and redox reversibility . These properties make the organic nitroxyl radical an ideal candidate for potential use in an ELHP.…”

Particle Size and Shape Effects in Electrochemical Environments: Pd Particles Supported on Ordered Co3O4(111) and Highly Oriented Pyrolytic Graphite

“…Earlier, we investigated the influence of the EMSI on the oxidation state and stability of well-ordered Co 3 O 4 (111) films and Pt/Co 3 O 4 (111) model catalysts by means of X-ray and synchrotron radiation photoelectron spectroscopies (XPS and SRPES) coupled with ex situ emersion EC cells. − We found that the stabilization mechanism involves a complex interplay between the particle size, the EMSI, and the dissolution process . In particular, we observed enhanced stability of ultrasmall Pt clusters for which the EMSI is the strongest .…”

2-Propanol Interacting with Co3O4(001):A combined AIMD and vSFS study

“…[7][8][9] In addition, the various electronic, magnetic and redox properties of Co 3 O 4 have also stimulated several studies in recent years. [10][11][12][13][14][15] Falk et al 1 studied the oxidation of 2-propanol over Co 1+x Fe 2-x O 4 spinel oxides in contact with both the liquid and the gas phase. They reported that increasing the Co content will increase the catalytic activity of the samples for 2-propanol oxidation, which shows that the iron-free Co 3 O 4 samples have the highest catalytic activity.…”