Berlin 2018 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 53: Energy materials (other than photovoltaics)

HL 53.5: Vortrag

Freitag, 16. März 2018, 10:30–10:45, EW 202

Photolytic water splitting by surface-conditioned n-GaP(100) photoanodes — •waqas saddique, gerhard lilienkamp, and winfried daum — Institute of Energy Research and Physical Technologies, Technical University Clausthal, Clausthal-Zellerfeld, Germany

III-V semiconductors are candidates for photoelectrochemical (PEC) water splitting but they are prone to corrosion and suffer from corrosion-related decrease of efficiency. Gallium phosphide (GaP) has an indirect band gap of 2.26 eV which covers both the hydrogen evolution potential (HEP) and the oxygen evolution potential (OEP). Thus, in principle, GaP can be used as photocathode and photoanode. We have studied the structural and chemical surface modifications of n-GaP(100) photoanodes before and after extended PEC treatment by scanning electron microscopy (SEM), atomic force microscopy (AFM), Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS). An approximately 2 nm thin stable oxide film is produced at the surface of n-GaP(100) photoanode via oxidizing the surface at 0.8 V vs RHE (reversible hydrogen electrode) and subsequent hydrogenation to passivate the electrically active defects in the oxide film. After appropriate surface-conditioning, PEC water splitting was observed at potentials between 0 and 0.3 V. After extended PEC treatment, AFM revealed a very flat surface, and no sign of corrosion were observed. XPS results indicate that the surface oxide consists mainly of Ga2O3, while small amounts of GaPO4, P2O5 and metal-like Ga are also present in the topmost layers.