Berlin 2018 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 70: Solid-liquid interfaces: Reactions and electrochemisty III (joint session O/CPP)

O 70.3: Vortrag

Mittwoch, 14. März 2018, 15:30–15:45, MA 144

Charge transfer across the n-GaP(100) photoanode/electrolyte interface during photoelectrochemical water splitting — •waqas saddique, gerhard lilienkamp, and winfried daum — Institute of Energy Research and Physical Technologies, Technical University Clausthal, Clausthal-Zellerfeld, Germany

A detailed understanding of charge transfer across the electrode/electrolyte interface is required for the development of electrodes for efficient water splitting. We have studied the charge transfer processes across the n-GaP(100) photoanode/electrolyte interface at different photoelectrochemical (PEC) conditions. In a 0.02 M HCl electrolyte, high photoanodic currents from n-GaP(100) photoanodes related to photolytic water splitting were measured at low anodic potentials, these currents diminished at cathodic potentials as well as at high anodic potentials. Nyquist plots obtained from electrochemical impedance spectroscopy (EIS) results were analyzed with two different equivalent electrical circuits (EECs) for the electrode/electrolyte charge transfer pathways. For both EECs, the potential dependence of resistances and constant phase elements were determined from fits to Nyquist plots and then compared with the potential variation of the current in the cyclic voltammogram. XPS measurements revealed that the surface oxide consists mainly of Ga2O3, while small concentrations of GaPO4, P2O5 and metal-like Ga are also detected in the topmost layers. Our results suggest that energetically favorable absorption of hydroxide, persumably at metal-like surface Ga, and their subsequent oxidation at low anodic potentials lead to high currents.