Option 1 suggests that non-metallic hydrides can accommodate a large volume of hydrogen. Non-metallic hydrides are compounds formed between hydrogen and non-metals. Examples include borane (BH3), ammonia (NH3), and methane (CH4). While these compounds can contain hydrogen, they do not have the capacity to accommodate a "very large volume" of it. Therefore, option 1 is incorrect.

Option 2, hydrogen peroxide (H2O2), is a compound consisting of hydrogen and oxygen. It is commonly used as a bleaching agent and disinfectant. However, hydrogen peroxide does not have the ability to accommodate a large volume of hydrogen. Thus, option 2 is incorrect.

Option 3, non-stoichiometric hydrides, refers to compounds that do not have a fixed ratio between the elements. These hydrides often have excess hydrogen, allowing them to accommodate a large volume of it. Examples include titanium hydride (TiHx) and vanadium hydride (VHx). Therefore, option 3 is correct.

Option 4 suggests that alkali metal hydrides can accommodate a large volume of hydrogen. Alkali metal hydrides, such as lithium hy