You will be shown an abstract from a biomedical research paper. Given this abstract, your task is to extract all unique entities of the following types: ["Chemical"].

Please return the output as a JSON object of the format: {"Chemical": ["Arsenic", ...]}. The keys should be entity types and values should be lists of extracted entities belonging to the corresponding type. If you cannot find entities belonging to a specific type, the value should be [].

Only output the JSON object and do not include any additional text.

Abstract:

Formation Mechanism of TiO 2 Nanotubes and Their Applications in Photoelectrochemical Water Splitting and Supercapacitors. Structural observations of the transition of TiO 2 nanopores into nanotubes by increasing the OH (-) concentration in the electrolyte challenge the validity of existing formation mechanisms of anodic TiO 2 nanotubes. In this study, dehydration of titanium hydroxide in the cell wall is proposed as the mechanism that leads to the separation of neighboring nanotubes. Based on this understanding, bamboo-type TiO 2 nanotubes with large surface area and excellent interconnectivity are achieved by cycling high and low applied potentials. After thermal treatment in a H 2 atmosphere, the bamboo-type TiO 2 nanotubes show large photoelectrochemical water splitting efficiency and supercapacitors performace.
{"Chemical": ["H 2", "TiO 2", "titanium hydroxide", "OH (-)"]}