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Issue 5, 2018
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Light-assisted electrochemical water-splitting at very low bias voltage using metal-free polythiophene as photocathode at high pH in a full-cell setup

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Abstract

We report the use of polyterthiophenes (PTTh) as a rare, combined light-harvester and catalyst for the hydrogen evolution reaction at high pH. Illuminated PTTh in combination with a MnOx anode in a two-electrode setup exhibited stable water-splitting at a bias-potential of only 0.3 V at pH 12. This confirms that PTTh used as photocathode can produce photovoltages of at least 900 mV for the hydrogen evolution reaction at high pH and is therefore a suitable match for traditional water-oxidation catalysts such as MnOx, CoOx, and RuOx. Films of PTTh were fabricated using a novel, metal-free method where iodine vapor is used as oxidant; thus, previously observed interference from metal residuals was omitted and thereby a gravimetric photo electrocatalytic conversion rate of 330 mmol(H2) h−1 g−1 was achieved in phosphate buffer (pH 7) at 0 V vs. RHE. A striking property of this new strand of polythiophene was an “inverse” correlation (compared to that predicted using the Nernstian relationship) between the onset potential for the light-assisted water reduction reaction and pH: the potential (vs. RHE) required for a given current was more positive at higher pH, which is not observed for other (photo-) electrocatalytic materials, and indicates that the charge neutralization of PTTh (rather than the pH) guides the onset potential.

Graphical abstract: Light-assisted electrochemical water-splitting at very low bias voltage using metal-free polythiophene as photocathode at high pH in a full-cell setup

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Publication details

The article was received on 29 Dec 2017, accepted on 23 Mar 2018 and first published on 04 Apr 2018


Article type: Paper
DOI: 10.1039/C7EE03669H
Citation: Energy Environ. Sci., 2018,11, 1335-1342
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    Light-assisted electrochemical water-splitting at very low bias voltage using metal-free polythiophene as photocathode at high pH in a full-cell setup

    K. Oka, O. Tsujimura, T. Suga, H. Nishide and B. Winther-Jensen, Energy Environ. Sci., 2018, 11, 1335
    DOI: 10.1039/C7EE03669H

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