Modulation of Charge Separation in TiO 2 Photoanode through Dual-Functional CoS as Sensitizer and Cocatalyst

Modifying oxide semiconductor with transition metal sulfide represents a promising strategy to simultaneously accelerate redox kinetics and improve photon capture efficiency. We decorate TiO 2 nanotubes with cobalt sulfide microspheres via anodic oxidation and hydrothermal methods. The reduced charge transfer resistance of 0.75 kΩ and lower activation energy of 15.9 kJ mol −1 are achieved, benefiting for carrier migration at electrolyte and electrode interface. CoS with excellent visible light response character significantly boosts photon convert efficiency and photogenerated carrier density. The electron lifetime and separation efficiency for CoS/TiO 2 photoanodes are increased 3.3 times and 1.4 times, respectively. The combination microsphere and nanotube structure provides abundant active sites and shorter depletion layer width, resulting in facile charge transfer from semiconductor interior to electrode surface. Dual functional CoS acts as both a light sensitizer and an electrochemical cocatalyst, which extend visible light absorption and timely extracts photogenerated electron/hole to suppress recombination via reversible chemical valence transition.