비스무트기반반도체를통한광촉매적에너지전환 – 실험적리뷰와물질합성및조사

Abstract

Photoelectrochemical cell for solar energy conversion is rapidly raising research subject as one of the renewable energy technology. Similarity with photosynthesis of nature utilizing sun’s energy provoked numerous researches for more than half of century. While now there are specific requirements for this technology to be practical like photovoltaic cell – cost balance of 1 kg solar hydrogen/10 $ and efficiency over 10 % (10 mW/cm2 from 100 mW/cm2 of 1 sun condition), it takes the proper material to realize such goals. Yet there are mere few (less than 10) reports claiming ideal reaction of complete infra independent photocatalysis to harvest solar energy and produce hydrogen and oxygen, which are carbon neutral, completely contaminant free energy, photoelectrochemical cell itself proposed much larger window of various material application by half-cell approach. Thus, material only has to meet one of the reaction amongst reduction or oxidation reaction by harvesting solar energy. While there are also countless materials to be effective, there are only few meeting all requirements for practical application – 1) price of material, 2) inherent stability, 3) environmental inertness and 4) photon harvesting & utilization efficiency by having favorable electronic structure (preferably 1.2~2.0 eV as band gap energy (Eg)). Recent development of BiVO4 (Eg = 2.6,direct~2.4 eV,indirect) as photoanode (photocatalyst loaded conductive substrate, for PEC oxidation reaction) showed that mere metal oxide could achieve unpresented solar energy utilization efficiency of 7.0 %. Characteristics of BiVO4 revealed that such functionality was from BiVO4’s specific chemical and electronic property caused by Bi element. Therefore, other not well studied Bi based semiconductors would probably have similar characteristics that can be next generation material for photoelectrochemical cell. Indeed, literature survey showed a lot of potent candidates –BiFeO3 (2.2 eV), BiOI (2.1 eV), CuBi2O4 (1.8 eV) et al as visible light active photocatalysts. This research’s goal is to confirm those materials’s property that whether they are suitable for PEC energy conversion or not and preferably find the proper successor of BiVO4, which is currently the champion metal oxide for PEC cell application.