“…Therefore, we turned our attention to another p-block metal oxide. In 2 O 3 , as a well-known semiconductor with a moderate band gap (E g = 2.8 eV), low toxicity, stable physicochemical, and visible-light-responsive property, has received extensive attention in photocatalytic degradation of organic pollutants and photo-splitting of water to produce hydrogen [25][26][27]. In addition, In 2 O 3 micro-/nanospheres with hollow interior could offer ideal geometrical architectures for photocatalytic applications, which is due to the fact that void space in hollow particles can be used to modulate refractive index, increase active area, lower density, as well as shorten ion diffusion path [28,29].…”