Carbon coated iron pyrite (C–FeS₂) photo-electrode for photo-electrochemical water splitting

In this paper, we present fabrication of ‘FeS₂’ and carbon coated FeS₂ (C–FeS₂) photo-electrodes and demonstrated that coating of carbon on FeS₂ significantly enhanced photo-electrochemical properties. The hydrothermal method has been adopted for the synthesis of FeS₂ and carbon coating on FeS₂ was achieved by CVD technique. The materials are subsequently characterized using X-ray diffraction, Raman spectroscopy and Field enhanced scanning electron microscope (FESEM) techniques for phase identification and morphological studies, respectively. The photo-electrochemical measurements revealed significant enhancement in the current density from ∼2 to 3.7 mA/cm² (∼1.8 times higher) for C–FeS₂ in comparison to the FeS₂ photo-electrode under visible light. The enhancement in FeS₂ after carbon coating has been attributed to reduction in recombination of photo generated charge carriers, enhancement in the band bending and lowering the charge transfer resistance at the semiconductor/electrolyte interface. To date, very few studies have been reported on FeS₂ based composites for water splitting applications and use of carbon coating can be a novel approach for developing efficient solar to hydrogen conversion devices. The mechanism for the photocurrent enhancement was supported by Mott-Schottky and electrochemical impedance spectroscopy measurements.