title: Efficient electrolyzer for CO2 splitting in neutral water using earth-abundant materials.
abstract: Low-cost, efficient CO2-to-CO+O2 electrochemical splitting is a key step for liquid-fuel production for renewable energy storage and use of CO2 as a feedstock for chemicals. Heterogeneous catalysts for cathodic CO2-to-CO associated with an O2-evolving anodic reaction in high-energy-efficiency cells are not yet available. An iron porphyrin immobilized into a conductive Nafion/carbon powder layer is a stable cathode producing CO in pH neutral water with 90% faradaic efficiency. It is coupled with a water oxidation phosphate cobalt oxide anode in a home-made electrolyzer by means of a Nafion membrane. Current densities of approximately 1 mA/cm(2) over 30-h electrolysis are achieved at a 2.5-V cell voltage, splitting CO2 and H2O into CO and O2 with a 50% energy efficiency. Remarkably, CO2 reduction outweighs the concurrent water reduction. The setup does not prevent high-efficiency proton transport through the Nafion membrane separator: The ohmic drop loss is only 0.1 V and the pH remains stable. These results demonstrate the possibility to set up an efficient, low-voltage, electrochemical cell that converts CO2 into CO and O2 by associating a cathodic-supported molecular catalyst based on an abundant transition metal with a cheap, easy-to-prepare anodic catalyst oxidizing water into O2.
authors.affiliation: Laboratoire d'Electrochimie Moléculaire, Unité Mixte de Recherche Université - CNRS No 7591, Université Paris Diderot, Sorbonne Paris Cité, 75205 Paris Cedex 13, France;
authors.forename: Arnaud
authors.initials: A
authors.lastname: Tatin
authors.affiliation: Unité Mixte de Recherche Université - CNRS No 7285, Université de Poitiers, 86022 Poitiers Cedex, France.
authors.forename: Clément
authors.initials: C
authors.lastname: Comminges
authors.affiliation: Unité Mixte de Recherche Université - CNRS No 7285, Université de Poitiers, 86022 Poitiers Cedex, France.
authors.forename: Boniface
authors.initials: B
authors.lastname: Kokoh
authors.affiliation: Laboratoire d'Electrochimie Moléculaire, Unité Mixte de Recherche Université - CNRS No 7591, Université Paris Diderot, Sorbonne Paris Cité, 75205 Paris Cedex 13, France; cyrille@univ-paris-diderot.fr robert@univ-paris-diderot.fr saveant@univ-paris-diderot.fr.
authors.forename: Cyrille
authors.initials: C
authors.lastname: Costentin
authors.affiliation: Laboratoire d'Electrochimie Moléculaire, Unité Mixte de Recherche Université - CNRS No 7591, Université Paris Diderot, Sorbonne Paris Cité, 75205 Paris Cedex 13, France; cyrille@univ-paris-diderot.fr robert@univ-paris-diderot.fr saveant@univ-paris-diderot.fr.
authors.forename: Marc
authors.initials: M
authors.lastname: Robert
authors.affiliation: Laboratoire d'Electrochimie Moléculaire, Unité Mixte de Recherche Université - CNRS No 7591, Université Paris Diderot, Sorbonne Paris Cité, 75205 Paris Cedex 13, France; cyrille@univ-paris-diderot.fr robert@univ-paris-diderot.fr saveant@univ-paris-diderot.fr.
authors.forename: Jean-Michel
authors.initials: JM
authors.lastname: Savéant
keywords: CO2-to-CO conversion; carbon dioxide electrolyzer; electrochemistry; molecular catalysis; solar fuels