Cold fusion has been debunked. Your best bet is to spend your time elsewhere. That said, the 'theory' behind 'cold fusion' was that the host material (Pd is I recall correctly) would adsorb hydrogen and in so doing would lower the nuclear barrier that the second nucleous would have to pass to come close enough to fuse. But this does not hold water.

Thanks a lot Sydney Ernest Grimm for your answer.

Thank you S. Alexiou

Although I am not an expert on the matter, the point is that nuclear sizes are of the order of fermis (10**-15 m). Lattice sizes are of the order of Angstroms (10**-10m). So you would need to 'trap' an immense number of hydrogen atoms in each lattce cell to get them to overcome the Coulomb repulsion and fuse and it is not at all clear how a metal, perhaps with a very good affinity would be able to do that. You see, affinity is a chemical function that happens on larger than Angstroms scales and here you want compression to nuclear scales, i.e. 5 order of magnitude smaller. Early experiments that claimed cold fusion have been debunked. For a brief summary of where this is now, you may look at https://www.scientificamerican.com/article/what-is-the-current-scien/