Optimized CoNi Nanoparticle Composition for Curie-Temperature-Controlled Induction-Heated Catalysis

Induction heating by magnetic hysteresis of nanoparticles inside chemical reactors is an interesting approach for direct and electrified heating of high-temperature endothermic catalytic reactions. Here, we show how it is possible to tune the induction heating for steam methane reforming by use of alumina-supported Co_xNi_(100-x) nanoparticles with well-defined alloy compositions from x = 20 to 90. The ∼30 nm Co-Ni particles function both as a catalyst and as an induction heating susceptor. We find that induction heating increases with increasing Ni content at lower temperatures and smaller induction fields due to Ni being magnetically softer than Co, but the maximum heating temperature increases with Co content due to the Curie temperature being higher for Co than for Ni. Specifically, the Curie temperature of the sample increases with the Co content and sets for each alloy a hard limit to the maximum operation temperature in the induction-heated reactor. Furthermore, the reaction rate increases with increasing Ni content. The compromise between magnetic softness, Curie temperature, and catalytic activity leads to an optimum Co-Ni sample composition at a given operating temperature and induction field amplitude. Based on the results, Co-Ni compositions can be selected in order to tune heat transport and reaction kinetics down through a reactor to optimize the reactor performance. Moreover, Co-Ni composition can be chosen such that the Curie temperature prevents overheating.