The problem is, they haven’t provided any details on how the process works. After their paper was rejected by several peer reviewed scientific journals, it was published in the Journal of Nuclear Physics-- an online journal apparently founded by Rossi and Focardi. Further, they say they can’t account for how the cold fusion is triggered, fostering deep skepticism from others in the scientific community.
Based on this lack of even a theoretical basis for the device’s function, a patent application was rejected. Their credibility isn’t helped by the fact that Rossi apparently has something of a rap sheet, which allegedly includes illegally importing gold and tax fraud.