a, b, Operation for 6,000 h on iso-butane and propane (cell 4). c, Operation for 1,400 h on methane. d, Operation for 6,000 h on iso-butane and propane (cell 4). The Tamman temperature of nickel is 581 °C. The target operating temperature of our PCFCs is lower than 600 °C, and most of the long-term stability testing conducted in this study was at 500 °C (that is, well below the Tamman temperature), at which Ni sintering/coarsening is avoided. Indeed, as shown in Extended Data Fig. 6c, d, the distribution and size of Ni nanoparticles on the BZY anode support remain essentially constant between 1,400 and 6,000 h of operation.