Photofunctional Construct That Interfaces Molecular Cobalt-Based Catalysts for H₂ Production to a Visible-Light-Absorbing Semiconductor

Abstract

Molecular cobalt-containing hydrogen production catalysts are grafted to a visible-light-absorbing semiconductor. The attachment procedure exploits the UV-induced immobilization chemistry of vinylpyridine to p-type (100) gallium phosphide (GaP). Single step surface-initiated photopolymerization yields a covalently attached polymer with pendent pyridyl groups that provide attachment points for assembling cobaloxime catalysts. Successful attachment is characterized by grazing angle attenuated total reflection Fourier transform infrared spectroscopy (GATR-FTIR), which shows distinct vibrational modes associated with the catalyst, as well as X-ray photoelectron spectroscopy (XPS) and X-ray absorption near edge structure spectroscopy (XANES) that confirm the presence of intact Co(III) complex on the surface. The Co-functionalized photocathode shows significantly enhanced photoelectrochemical (PEC) performance in aqueous conditions at neutral pH, compared to results obtained on GaP without attached cobalt complex. PEC measurements, at 100 mW cm(-2) illumination, yield a 2.4 mA cm(-2) current density at a 310 mV underpotential.