Highly efficient utilization of light and charge separation over a hematite photoanode achieved through a noncontact photonic crystal film for photoelectrochemical water splitting

The trade-off problem between light absorption and charge collection under lower band-bending (bias) is extremely difficult to resolve in water splitting on photoelectrodes. Although the use of metallic back-reflectors, antireflection coatings, and textured substrates and light absorbers enable the improvement of light utilization efficiency, these methods still suffer from high cost and complex fabrication process, especially, incompetent separation of photogenerated carriers. Here taking the hematite (α-Fe2O3) photoanode as a model, we report that a noncontact photonic crystal (PC) film composed of silica nanoparticles and ethoxylated trimethylolpropane triacrylate (ETPTA) resin can significantly enhance the photoelectrochemical (PEC) activity of the photoelectrode. Specifically, more than 250 mV cathodic shift in the onset potential and 4 times larger photocurrent at 1.0 V versus a reversible hydrogen electrode (RHE) were achieved over the α-Fe2O3-PC photoanode hybrid system, compared with the pristine α-Fe2O3 photoanode. Our work showed that a PC film not only boosted light absorption of the α-Fe2O3 layer but also improved its charge transfer efficiency under light illumination. These new findings of the synergistic effect will open a new avenue to design high-performance solar energy conversion devices.