Improving bioelectrochemical performance by sulfur-doped titanium dioxide cooperated with Zirconium based metal–organic framework (S-TiO2@MOF-808) as cathode in microbial fuel cells

The sulfur-doped titanium dioxide (S-TiO2) cooperated with Zirconium based on a kind of metal–organic framework (MOF-808) was successfully prepared as cathode catalyst (S-TiO2@MOF-808) of microbial fuel cell (MFC) by two-step hydrothermal reaction. The particle size was approximately 5 μm, and the spherical S-TiO2 particle was attached to the surface of MOF-808 as irregular block solid. Zr-O, C-O and O-H bond were indicated to exist in S-TiO2@MOF-808. When n (Zr4+): n(Ti4+) was 1: 5, S-TiO2@MOF-808 showed better oxygen reduction reaction (ORR). The introduction of S-TiO2 restrained the framework collapse of MOF-808, S-TiO2@MOF-808 showed much higher catalytic stability in reaction. The recombination of sulfur and TiO2 reduced the charge transfer resistance, accelerated the electron transfer rate, and improved ORR greatly. The maximum power density of S-TiO2@MOF-808-MFC was 84.05 mW/m2, about 2.17 times of S-TiO2-MFC (38.64 mW/m2). The maximum voltage of S-TiO2@MOF-808-MFC was 205 mV, and the stability was maintained for 6 d.