CdS sensitized sol-gel derived thin films of self-patterned micro-blocks of closely-packed SnO2 nanoparticles as high-performance photoanodes in alkaline solution of methanol

Abstract Materials with patterned micro-/nano-structures fabricated via self-organization for the conversion and utilization of solar energy are attractive. Thin films of self-patterned irregular micro-blocks of closely packed SnO 2 nanoparticles have been achieved here as photoanodes in photoelectrochemical cells for the first time, which are accomplished facilely by annealing SnO 2 gel coatings on conducting glass substrates at 500 °C. During the annealing, the gel coating evolves into closely packed SnO 2 nanoparticles. They self-assemble into irregular micro-blocks (mostly about 10 μm in size), generating dense network micro-cracks (∼2 μm wide in average) around the micro-blocks and nano-cracks embedded in the micro-blocks due to the thermal contraction stress that the SnO 2 nanocrystallization and self-assembly induce. Optimally, the self-patterned SnO 2 film is well sensitized with nanolayers of CdS nanoparticles by successive ionic layer adsorption and reactions for six cycles. Under optimized conditions, the prepared SnO 2 /CdS film demonstrates an apparent anodic photocurrent density as high as 10 mA cm −2 while holding the potential at 0 V (vs. SMSE) in a photoelectrochemical cell with 2 M NaOH +1 M methanol under visible light illumination of 100 mW cm −2 , which is among the highest record for SnO 2 /CdS photoanodes. We ascribe its high performance not only to the patterned micro/nano-structure and the type-II energy level alignments of the SnO 2 /CdS photoanode, but also to the photo-electro synergistic catalyses in methanol oxidation reaction.