Structural transformation of carbon-encapsulated core-shell CoNi nanoparticles during magnetically induced CO₂ reduction into CO

Controlling product distribution in CO2 hydrogenation is of great scientific interest, the selective CO production through the reverse water-gas shift reaction (RWGS) being one of the most investigated processes. Herein, we report the synthesis of new core-shell Co@Ni NPs encapsulated in carbon (Co@Ni@C) to prevent their aggregation at the high-temperatures reached during magnetically induced catalysis. This bifunctional system has been simultaneously used as heating agent and catalyst for the magnetically induced hydrogenation of CO2. While at low magnetic fields Co@Ni@C produces CH4:CO mixtures, at higher field amplitudes it selectively generates carbon monoxide. Indeed, Co@Ni@C has shown to be one of the most active catalysts reported to date, which reaches a maximum conversion of 74.2% with complete selectivity towards CO at 53 mT and 300 kHz. In addition, recycling and cyclability experiments have demonstrated that Co@Ni@C becomes fully selective for CO after being exposed to high field amplitudes (i.e. reaction temperature above 500 degrees C), even when it exposed to low magnetic fields again. This change in the selectivity is due to an atomic rearrangement of the core-shell structure, as was confirmed by EDX, XAS, TPR and TPD analysis.