Enhanced Photoelectrochemical Water Splitting through Bismuth Vanadate with a Photon Upconversion Luminescent Reflector

Abstract

Abstract As the performance of photoanodes for solar water splitting steadily improves, the extension of the absorption wavelength in the photoanodes is highly necessary to substantially improve the water splitting. We use a luminescent back reflector (LBR) capable of photon upconversion (UC) to improve the light harvesting capabilities of Mo:BiVO 4 photoelectrodes. The LBR is prepared by dispersing the organic dye pair meso ‐tetraphenyltetrabenzoporphine palladium and perylene capable of triplet–triplet annhilation‐based UC in a polymer film. The LBR converts the wavelengths of 600–650 nm corresponding to the sub‐band gap of Mo:BiVO 4 and the wavelengths of 350–450 nm that are not sufficiently absorbed in Mo:BiVO 4 to a wavelength that can be absorbed by a Mo:BiVO 4 photoelectrode. The LBR improves the water splitting reaction of Mo:BiVO 4 photoelectrodes by 17 %, and consequently, the Mo:BiVO 4 /LBR exhibits a photocurrent density of 5.25 mA cm −2 at 1.23 V versus the reversible hydrogen electrode. The Mo:BiVO 4 /LBR exhibits hydrogen/oxygen evolution corresponding to the increased photocurrent density and long‐term operational stability for the water splitting reaction.