posted on 2020-01-11, 15:23authored byJonnathan C. Hidalgo-Acosta, Micheál D. Scanlon, Manuel A. Méndez, Véronique Amstutz, Heron Vrubel, Marcin Opallo, Hubert H. Girault
Electrocatalysis of water oxidation was achieved using fluorinated tin oxide (FTO) electrodes modified
with layer-by-layer deposited films consisting of bilayers of negatively charged citrate-stabilized IrO2
NPs and positively charged poly(diallyldimethylammonium chloride) (PDDA) polymer. The IrO2 NP
surface coverage can be fine-tuned by controlling the number of bilayers. The IrO2 NP films were
amorphous, with the NPs therein being well-dispersed and retaining their as-synthesized shape and
sizes. UV/vis spectroscopic and spectro-electrochemical studies confirmed that the total surface
coverage and electrochemically addressable surface coverage of IrO2 NPs increased linearly with the
number of bilayers up to 10 bilayers. The voltammetry of the modified electrode was that of hydrous
iridium oxide films (HIROFs) with an observed super-Nernstian pH response of the Ir(III)/Ir(IV) and
Ir(IV)–Ir(IV)/Ir(IV)–Ir(V) redox transitions and Nernstian shift of the oxygen evolution onset potential. The
overpotential of the oxygen evolution reaction (OER) was essentially pH independent, varying only from
0.22 V to 0.28 V (at a current density of 0.1 mA cm 2), moving from acidic to alkaline conditions. Bulk
electrolysis experiments revealed that the IrO2/PDDA films were stable and adherent under acidic and
neutral conditions but degraded in alkaline solutions. Oxygen was evolved with Faradaic efficiencies
approaching 100% under acidic (pH 1) and neutral (pH 7) conditions, and 88% in alkaline solutions (pH 13).
This layer-by-layer approach forms the basis of future large-scale OER electrode development using ink-jet
printing technology.
History
Publication
Physical Chemistry Chemical Physics;18, pp. 9295-9304