Acid etching method for improving specific surface area of titanium black and doped titanium black powder

The invention relates to an acid etching method for improving the specific surface area of titanium black and doped titanium black powder. The acid etching method has two technical schemes. According to the first scheme, raw materials are low-specific-surface-area titanium black powder or low-specific-surface-area doped titanium black powder and at least one of an HCl aqueous solution, an H2SO4 aqueous solution and an HNO3 aqueous solution, the raw materials are evenly mixed to form feed liquid, then the feed liquid is poured into a reaction kettle and put into a heating furnace, the temperature is increased to 130-150 DEG C, a hydrothermal reaction is conducted, and the reaction kettle is cooled to the room temperature to obtain the titanium oxide/doped titanium black composite material. And then centrifugally washing the reaction product with deionized water and absolute ethyl alcohol in sequence to remove acidic substances, and then drying. According to the second scheme, low-specific-surface-area titanium