Diborane upon hydrolysis gives

Hydrolysis of diborane gives hydrogen gas and orthoboric acid (or boric acid). Hydrolysis of diborane is:

${\mathrm{B}}_2{\mathrm{H}}_6+6{\mathrm{H}}_2\mathrm{O}\to \underset{\mathrm{Orthoboric} \mathrm{acid}}{2{\mathrm{H}}_3{\mathrm{BO}}_3}+{\mathrm{H}}_2$