Selectively monitoring the operando temperature of active metal nanoparticles during catalytic reactions by X-ray absorption nanothermometry

Heat involved in catalytic reactions can influence the local temperature and performance of the active site, potentially causing catalyst degradation and runaway scenarios. Yet, broadly applicable thermometry methods to selectively probe the temperature of the catalytically active phase—where reactions take place—are generally lacking. Here we explore extended X-ray absorption fine-structure thermometry to monitor the operando temperature of active Ni nanoparticles, fully deconvoluted from their metal-oxide support. During dry reforming of methane, the reaction’s endothermicity causes Ni nanoparticles to become local heat sinks with their temperature deviating 90 °C from the reactor temperature. By thermometry at the single nanoparticle level, we chart the energy balance of nanoparticles and relate their temperature to reaction kinetics. Covering the full temperature range relevant to catalysis, this broadly applicable method enables temperature monitoring of individual catalyst components separately. Applying extended X-ray absorption fine-structure thermometry to existing datasets worldwide can generate enhanced understanding on reaction-induced temperature phenomena in heterogeneous catalysis. Monitoring the temperature of a catalyst’s active site during reactions can offer important insights into reactivity, but broadly applicable methods are lacking. Here the authors evaluate the potential of extended X-ray absorption fine-structure thermometry to observe variations in the temperature of nickel nanoparticles throughout representative gas–solid reactions.