Solid oxide fuel cells (SOFCs) transform chemical energy to electrical energy by an electrochemical conversion process with less CO₂ emission in comparison to most other conventional power generation systems. Ni-based composite (Ni-cermet) has been widely used as a SOFC anode material because of the excellent catalytic activity and electrical conductivity of Ni. However, Ni-based anode suffers from carbon build-up (coking), sulfur poisoning and low stability to redox cycling [1]. Among the alternative materials that have been studied, the layered perovskite manganites, LnBaMn₂O_5+δ (Ln = Pr, Nd) continue to attract attention [2-4]. The electrocatalytic activity of LnBaMn₂O_5+δ materials can be improved by in situ formation of Ni-nanoparticles which has been monitored by high temperature neutron powder diffraction (NPD) under hydrogen. These results complement electron microscopy characterizations.