Photoautotroph: An autotroph that can synthesize its own organic matter from carbon dioxide, water and other inorganic substances with the help of pigments and sunlight.

In autotrophs, plankton can use the energy released by some chemical reactions to synthesize their own organic matter from alkanes, hydrogen sulfide and inorganic substances without light energy.

The above is taken from Baidu Encyclopedia's definitions of photoautotrophs and chemoautotrophs. According to their definition, photoautotrophs contain water, inorganic salts and so on. Chemotactic autotrophs also need them. the difference is

Chemotactic autotrophs need chemicals such as alkanes and hydrogen sulfide to provide them with energy.

(This is the main difference. Different substances will be added to different chemoautotrophic biological media to provide energy, as well as some other inorganic salts and vitamins. The specific experiment is analyzed. )