Black TiO₂: What are exact functions of disorder layer

Among the substantial amount of photocatalyst materials, TiO₂ has been enthusiastically studied for a few decades due to its outstanding photocatalytic activity and stability. Recently, black TiO₂ consisting of approximately 2 nm of thin disorder layer around the surface showed surprisingly high solar hydrogen generation ability. The disorder layer of TiO₂ can enhance its light absorption, charge separation, and surface reaction abilities, however exact fundamentals of photocatalytic water-splitting pathways are still ambiguous. Herein, recent progress and investigations on exact functions of disorder layer and its application in photocatalytic CO₂ reduction will be discussed. Throughout the comprehensive studies on disorder layer of TiO₂, disorder engineering on photocatalyst materials will suggest the further extension of developing solar-fuel production technologies.