Which of the following types of catalyst is glycerol in the given reaction?

$2H_2{O}_2\mathit{ }\stackrel{\mathit{G}\mathit{l}\mathit{y}\mathit{c}\mathit{e}\mathit{r}\mathit{o}\mathit{l}\mathit{ }}{\mathit{\to }}2H_{2}O+O_2$

Glycerol is a negative catalyst in the given reaction.
$2H_2{O}_2\mathit{ }\stackrel{\mathit{G}\mathit{l}\mathit{y}\mathit{c}\mathit{e}\mathit{r}\mathit{o}\mathit{l}\mathit{ }}{\mathit{\to }}2H_{2}O+O_2$
A substance that doesn’t undergo any internal chemical change but increases the rate of the chemical reaction is known as a catalyst.
A catalyst is said to be a positive catalyst if it increases the rate of the reaction and a negative catalyst is a catalyst that decreases the rate of the reaction. It is clear that glycerol is responsible for decreasing the reaction rate; hence glycerol in the above reaction is a negative catalyst.