I understand that hydrogen peroxide (HTP) can be decomposed into superheated steam and oxygen using a catalyst, but I haven't been able to find any information on whether or not it will decompose in extreme heat, such as in a combustion chamber. I am aware that the rate of passive decomposition increases with temperature, but does it become instantaneous and feasible for combustion without instability?
HTP will sustain a combustion reaction without a catalyst once ignited, but it's not clear to me if the reaction proceeds quickly and smoothly enough to be a good idea for rocket combustion chambers.
As MSalters comments above, hydrogen peroxide "will undergo potentially explosive thermal decomposition" before reaching its theoretical boiling point, which is a very modest 423 K (150 ºC).
I found a good article on the topic: Thermal Decomposition of Hydrogen Peroxide, Part 1: Experimental Results. The details are somewhat beyond me but it looks like getting smooth and stable combustion was not easy.