Electrodeposition of Cu₂o/MoS₂ Thin Films on Fto Substrate As a Heterojunction Photoelectrochemical Cell for Water Splitting

Abstract

The layered structure MoS 2 , an n-type conductor (bandgap of 1.9-2 eV), can be excited under irradiation with visible light. However, its valence band energy (-4.2 eV) is closed to the minimum energy required to reduce water into hydrogen (- 4.2 eV at pH = 7). The p-type semiconductor Cu 2 O (a bandgap of 2 eV) has a valence band energy of - 4.0 eV, higher than that of MoS 2 and therefore has potentially as photocatalytic for water splitting. In this work, the heterojunction of Cu 2 O/MoS 2 is prepared on a conductive FTO-coated glass substrate by electrodeposition methods. We conduct initially the MoS 2 thin film on FTO by cyclic voltammetry (CV). Then, the Cu 2 O thin film is deposited on the MoS 2 /FTO thin film by double-potential pulse chronoamperometric (DPPC) to form a p-n junction Cu 2 O/MoS 2 /FTO photo-electrode which play an anodic role in a photoelectrochemical cell. The structure, morphology and composition of heterojunction electrode are characterized by powder X-ray diffraction, SEM, TEM, IR, Raman spectroscopy, electrochemical impedance spectroscopy (EIS). The optical properties are determined by UV-VIS spectroscopy and Photoluminescence (PL) spectroscopy. The photoelectrochemically catalytic activity of the electrodes is performed in dark condition and light condition with 1.5 AM from a solar simulator system by Linear-sweep voltammograms and Transient photocurrent-time methods. The H 2 -generation yield is evaluated by gas chromatography. The effect of the structure and the composition of the Cu 2 O/MoS 2 thin films on the kinetics and mechanism of the photoelectrochemical water splitting is also considered.