Chemical Vapor Deposition of Crystalized Nanoscale α-SnWO4 Thin Films and Their Photoelectrocatalytic Properties
Photoelectrochemical (PEC) systems provide a cost-effective strategy to harvest solar power into green fuels and valuable chemicals. Among various candidate materials for the light-absorbing layer in PEC photoanodes, n-type α-SnWO4 is quite attractive owing to its favorable band positions and decent visible light absorption. Although thin films are the most widely reported type of PEC photoelectrodes, up to now, only very few physical deposition techniques were realized for α-SnWO4 PEC structures. Herein, we demonstrate a chemical vapor deposition (CVD) strategy for high-quality α-SnWO4 thin films for PEC applications. This route features unsophisticated instrumentation, and, more importantly, a chemical process uniformly reacting vaporized SnCl2 with a predeposited WO3 layer on substrates. Homogeneous and phase-pure thin films can be obtained with controllable thickness (260–560 nm) and excellent visible light absorption. The nanoscale film was confirmed with decent intrinsic structural durability, as confirmed by a stable PEC photocurrent output. We also tentatively demonstrated the successful surface modification of a catalytic overlayer on this nanoscale film, which is desired for the efficient extraction of charge carriers. This CVD route first demonstrates a paradigm for preparing metastable oxide thin films, which are of particular interest for PEC and other optoelectronic applications.
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