De-pollution system fault?

Hi everyone, yes I have what seem to be a very common problem, with my Peugeot 307, for the first time. My son was using the car at the time when the car cut out on the motorway no power at all for about 25/30 mins then all ok the car started, he drove for about another 25 miles home. I could not find any info in the handbook ( now I know why). I have looked at and read all the questions and answer,BUT!,can't make head or tail of the answers!!!!!!! could be this or that and so on. Can anyone help and tell me what is the meaning of the fault, and how to repaire it, if at all.
Thank you to all that may replay and give advice

Carol B