Can we determine rate of reaction of spontaneous reaction by addition of suitable negative catalyst?if yes then how // if no then why?

See your question is nice 

But according to your question,you are asking that to detrmine the rate by adding catalyst,but catalyst will not either decrease or increase the rate because it is independent of the rate of the reaction and it will not matters whether it is either negative nor positive catalyst,

Why it is independent because of the follwing reasons i will explain you

1.it depends on reactants

2.and surface area will matters not the catalyst

3.and as you are asking bout spontaneous reactions they are very fast and NOT FEASIBLE

this reason is very important

so catalyst has no work to do thefre so we cannot determine the rate of the reaction by simply adding adding catalyst beneath that the above reasons will detrmine the rate of the reaction and not the catalyst \

and also caytalyst will not consume during the reaction that is also important

THANK YOU