The effect of carboxylated multiwall carbon nanotubes on the performance of camphor sulfonic acid doped polyaniline –WO3 nanocomposite as photoanode for solar photo electrochemical water splitting

Photo electrochemical (PEC) water splitting is an efficient and ecofriendly technique for producing hydrogen as clean energy source [1]. In this regard, researchers are focused on metal oxides and their nanocomposites as semiconductor materials for PEC cells [2]. In this research, camphor sulfonic acid doped polyaniline –WO3 (CSA PANI-WO3) and camphor sulfonic acid doped polyaniline –WO3-MWCNT (CSA PANI-WO3-CNT) nanocomosites were synthesized via in situ oxidative polymerization and used as photoanodes in PEC cell under solar illumination. The synthesized nanocomposites were characterized with Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) and Field emission scanning electron microscopy (FESEM). The Photo electrochemical measurements were conducted with Origa Flex-OGA 01A Potentiostate/Galvanostate using the thin films of CSA PANI-WO3 and CSA PANI-WO3-CNT on FTO conductive glasses as the photoanode, saturated calomel electrode (SCE) as the reference electrode and Pt plate as the counter electrode, respectively in 0.1 M Na2SO4 solution. The photo electrochemical tests were carried out in the dark and under illumination of Xenon lamp (300 W). The linear sweep voltammetry (LSV) was measured at -0.1- 1.6 V with 0.05 V/s scan rate. The electrochemical impedance spectroscopy (EIS) test was done in the frequency range of 100 kHz-100 mHz with AC amplitude of 10 mV. The Mott Schottky (M-S) analysis was performed in the -0.8 – 0.8 V vs SCE at fixed frequency of 1 kHz. The photocurrent density of CSA PANI-WO3-CNT (2.65 mA/cm2) is 1.42 times higher than CSA PANI-WO3 (1.87 mA/cm2). The higher photocurrent density of CSA PANI-WO3-CNT is due to the increase of the separation efficiency of electron-hole pairs and better electron transfer owing to MWCNT. The positive value of the slope of the M-S curves confirm the n-type semiconducting behavior of both nanocomposites having electrons as the majority carriers. Also, the charge transfer resistance (Rct) of CSA PANI-WO3-CNT is 1499 Ωcm2 which is lower than CSA PANI-WO3 (5375 Ωcm2) indicating the improvement of photoelectrocatalytic performance in the presence of MWCNT.