Lewis acid catalysis of polydopamine electropolymerisation as a tool for shaping its morphology and electrochemical properties

Abstract

Organic–inorganic semiconductor interfaces are of utmost importance in many photoelectrochemical applications, including water splitting and photodegradation of pollutants. The current work focuses on the fabrication and characterisation of transition metal-loaded polydopamine (PDA) electropolymerised on the surface of titania nanotubes. The structural studies via X-ray photoelectron spectroscopy and electron microscopy confirmed the catalytic effect of d-metal salts on the formation of the PDA layer during electropolymerisation. Cu and Ni loading leads to a significant enhancement of the visible absorption compared to that of the pristine PDA, also confirmed by the density functional theory calculations. Although the boost is greater for the thickest coatings, an excess amount of polymer suppresses the charge transfer and thus photocurrent generation. Synthesis in acidic conditions—optimal for photosensitisation—provides structures with a strong increase in the photocurrent quantum efficiency in the visible range, equal to 20% at 400 nm.Graphical