Application of carbon microfiber felts as three-dimensional conductive substrate for efficient photoanodes of tungsten(VI) oxide

Abstract

In the present study, a conductive carbon microfiber felt (CMF) with three-dimensional structure of carbon fibers (CFs) was employed as a conductive substrate of visible light responsive WO3 photoanodes for oxidative decomposition of organic contaminants and oxidation of water to molecular oxygen (O2). Since the surface of original CFs in CMF are highly hydrophobic, the pretreatment of CMF and the composition of W-precursor solution significantly affected the morphology and the resulting performance of photoanodes. The preheating of CMF at optimal temperature (640 °C) in air make the surface of CFs hydrophilic substantially while maintaining the mechanical strength of CMF structure, enabling the better impregnation of a water-soluble tungsten precursor, ammonium metatungstate (AMT) solution. The addition of polyethylene glycol 300 (PEG) to the precursor solution further improved the affinity to the surface of CFs, resulting in homogeneous loading of fine WO3 particles preferentially on the surface of CFs as well as in the voids of CFs to some extent. The results on optimization of loaded amount of WO3 of CMF from various precursor solutions indicated that both the WO3 particles loaded on the surface of CFs and those in the voids contribute to the photocurrent generation, while the efficiency of electron injection from WO3 on the CFs seems higher. Consequently, the optimized WO3/CMF photoanode exhibited higher photocurrent compared to conventional porous WO3/FTO photoanodes. It was demonstrated that a WO3 photoanode prepared on CMF could efficiently oxidize water to O2 with considerably high stability under visible light, not only for oxidation of 2-propanol.