Photoelectrochemical properties of InN nanowire photoelectrodes for solar water splitting

InN nanowires were grown on Si(111) substrates by plasma-assisted molecular beam epitaxy. Raman spectroscopy showed that the nanowires were strain-free and allowed the deduction of a free carrier concentration of 1–2 × 10 18 cm −3 . This value was confirmed by a Mott–Schottky analysis of electrolyte-based capacitance-voltage measurements. In addition, these measurements directly revealed the existence of a surface accumulation layer in the InN nanowires. In cyclic voltammetry measurements under irradiation from a Xe lamp with about 100 mW cm −2 , high photocurrents of about 4 and 11 mA cm −2 were observed at 1.23 and 1.63 V bias potential versus reversible hydrogen electrode, respectively, using H 2 O 2 as a hole scavenger. By comparing the photocurrent with and without H 2 O 2 , the main limiting factor in the performance of InN nanowire photoanodes was identified to be the poor catalytic efficiency for water oxidation at the surface, followed by parasitic bulk recombination.