TG/DTA-MS evaluation of methane cracking and coking on doped nickel-zirconia based cermets

Abstract

Cermet materials based on metallic nickel and cubic zirconia are the key material for applications on solid oxide fuel cells and high temperature water electrolysis. The main advantage is the possibility of direct feeding a hydrocarbon fuel, like methane, or even an alcohol as a source of hydrogen. The reforming reaction on the Ni catalyst surface can produce hydrogen continuously. However, the resulting catalyst poisoning by carbon deposition (coking) imparts their broad application. The work shows the evaluation of coking tolerance of some cermets prepared by mechanical alloying techniques and compares new additives specially chosen in order to avoid coking and increase the catalytic activity. Refractory metal additives besides copper were added to the basic cermet. While copper is a known doping agent that avoids coking, the refractory metals (Mo and W) have a twofold effect: promote sintering at lower temperatures and increase Cu activity due to their mutual immiscibility. Results of TG/DTA-MS analysis demonstrate both refractory metals have increased the coking tolerance as well as the catalytic activity during diluted methane cracking. Molybdenum and tungsten additives are promised regarding the improvement of these cermet materials for high temperature electrochemical devices.