Sure, you can. It is sort of photocatalytic reduction process. You can refer to this paper. Enhanced Photocatalytic Property of Reduced Graphene Oxide/TiO2 Nanobelt Surface Heterostructures Constructed by an In Situ Photochemical Reduction Method, small, 2014, 10(18), 3775–3782. 

Article Enhanced Photocatalytic Property of Reduced Graphene Oxide/T...

 Dear Prof. Sang

Thanks for reply. I need to use rGO/TiO2 in photocatalytic degradartion of pollutants. I am afraid that the activity of titania decrease because titania will use their electrons in reduction of graphene oxide.

Regards, 

Activity of Titania may reduce in with time, but not because of reduction of graphene oxide as your graphene oxide (rGO) is already in reduced  state.

Yes, definitely you can use UV irradiation for this. This is simply photocatalytic reduction of GO into rGO using TiO2 in the hybrid. But you need to optimize for improved activity.

Dear Prof. Mohapatra

thanks for your reply, but what do you mean by "you need to optimize for improved activity" and what about the dispersion of TiO2/GO before irradiation with UV. i already prepared TiO2/GO as a powder and I want to reduce it using this method.

Regards,

Yes you can. I don't think the activity of titania will be reduced but one thing I'm quite sure the rGO will prevent electron-hole recombination on TiO2 thus make TiO2 more efficient during photocatalytic process.

I would like to add in the discussion that if GO is reduced to rGO in-situ by the activity if TiO2 , however its activity will sufficiently be reduced due to following facts -

1. there will always be chances of having structural defects as the reduction process will not be there with 100% efficiency.

2. The photocatalytic degradation of pollutants will be quite time consuming as first there will be reduction of GO into rGO and then the e entrapment will take place, thus overall efficiency will reduce significantly.