Semiconductor particles used in water-splitting photocatalyst, photocatalyst formed of semiconductor particles, and synthesis method thereof

A synthesis method of semiconductor particles including strontium titanate in a photocatalyst for inducing a water-splitting reaction where water molecules decompose into oxygen molecules and hydrogen molecules by light irradiation, the photocatalyst being formed by adding a co-catalyst to the semiconductor particles including strontium titanate, and the synthesis method comprising a synthesis step of synthesizing the semiconductor particles including strontium titanate doped with scandium and aluminum by mixing strontium chloride (SrCl2), strontium titanate (SrTiO3), scandium oxide (Sc2O3), and aluminum oxide (Al2O3) to obtain a mixture and firing the mixture,

• wherein in the synthesis step, the scandium oxide is mixed at a molar ratio of 0.001 to 0.007 with respect to strontium titanate.