Black titanium dioxide (TiO₂) has been one of the most researched photocatalyst in recent years. Its ability to overcome the limitations of pristine TiO₂ through enhanced visible light absorption and reduced recombination of photogenerated charge carriers have gathered the attention of the scientific community since its discovery in 2011. Numerous synthesis routes have been developed for black TiO₂ owing to its superior activity as compared to pristine white TiO₂ in various applications. Extensive studies have enabled understanding its superior activities and most studies reveal that defect species like Ti³⁺ and oxygen vacancies are responsible for the enhanced photoactivity. However, closer look reveals that mere presence of defects does not necessarily lead to improved performance of black samples. Studies show that the same defect species can have negative impact on its performance. In fact, different factors like defect concentration, defect location, valence band and conduction band levels, synthesis route, synthesis conditions, anatase/rutile ratio etc play a key role in the working mechanisms of Black TiO₂ samples. In some cases, black TiO₂ samples have actually shown reduced photoactivity as compared to the pristine ones. All of these have led to some conflicting ideas related to role of defects in overall photoactivity, photoactivity under visible spectrum, existence/co-existence of Ti³⁺ species and oxygen vacancies and their location, connection between band gap values and photocatalytic activity etc. The intricacies of Black TiO₂ are yet to be thoroughly understood as evidently seen in the differing properties reported in many studies. This review summarizes the significant properties of black TiO₂ and identifies some of the conflicting points observed in literature where further light needs to be shed for better understanding.

黑色二氧化钛（TiO ₂）近年来已成为研究最多的光催化剂之一。自2011年被发现以来，其通过增强可见光吸收和减少光生电荷载流子的重组而克服了原始TiO ₂局限性的能力引起了科学界的关注。由于其优越的性能，已为黑色TiO ₂开发了许多合成途径。与原始白色TiO ₂相比，在各种应用中具有较高的活性 广泛的研究使人们能够了解其优越的活动，大多数研究表明，Ti ³⁺等缺陷物种和氧空位是导致光活性增强的原因。然而，仔细观察发现，缺陷的存在并不一定会导致黑色样品性能的提高。研究表明，相同的缺陷种类可能对其性能产生负面影响。实际上，缺陷浓度，缺陷位置，价带和导带能级，合成路线，合成条件，锐钛矿/金红石比等不同因素在黑色TiO ₂样品的工作机理中起着关键作用。在某些情况下，黑色TiO ₂与原始样品相比，样品实际上显示出降低的光活性。所有这些都导致了一些相互矛盾的观点，这些缺陷涉及整体光活性中的缺陷作用，可见光谱下的光活性，Ti ³⁺物种和氧空位的存在/共存及其位置，带隙值与光催化活性之间的联系等。从许多研究报告的不同性能中可以明显看出，黑色TiO ₂的复杂性尚未得到彻底理解。这篇综述总结了黑色TiO ₂的重要性能， 并指出了文献中观察到的一些矛盾之处，需要进一步阐明光线以便更好地理解。