Immobilising a cobalt cubane catalyst on a dye-sensitised TiO2 photoanode via electrochemical polymerisation for light-driven water oxidation

Abstract

A simple and effective method to prepare photocatalytically active electrodes for water oxidation is described in this paper. The precious-metal-free catalyst, Co₄O₄(O₂CMe)₄(4-vinylpy)₄ (py = pyridine) was electrochemically polymerised on a RuP-sensitised TiO₂ (RuP = [Ru(bpy)₂(4,4′-(PO₃H₂)₂bpy₂)]Cl₂) and on a TiO₂ surface codecorated with vinyl phosphate (Vpa) and RuP for applications in molecular photoelectrochemical (PEC) devices. With a Vpa chain as the anchoring group, the photoanode poly-Co₄O₄+Vpa/RuP/TiO₂ demonstrated a significantly higher PEC performance compared to poly-Co₄O₄/RuP/TiO₂. The introduction of a Vpa chain allows better immobilisation of catalyst and enhances the electron transport between the photosensitiser and the catalyst. A photocurrent density of ∼100 μA cm⁻² was achieved in a Na₂SO₄ solution at pH 7.0 under a 0.4 V external bias, with a faradaic efficiency of 76% for oxygen production.