Scalable method for the preparation of Co$_x$Ni$_{1-x}$/alumina nanocomposites and their magnetic heating propertiesSedminek, Anja (Avtor) Makovec, Darko (Avtor) Teržan, Janvit (Avtor) Likozar, Blaž (Avtor) Jenuš, Petra (Avtor) Kocjan, Andraž (Avtor) Marolt, Gregor (Avtor) Gyergyek, Sašo (Avtor) CoNi alloynanocompositemagnetic nanoparticlesmagnetic heatingmagnetic catalysisMagnetic nanocomposites with a high surface area matrix are attractive materials for novel catalyst supports. They can be remotely and selectively heated inside the reactor vessel when exposed to a high-frequency alternating magnetic field (AMF). These so-called "magnetic" or "cold" catalysts can revolutionize the chemical industry’s electrification, particularly for renewable energy applications such as hydrogen storage and release. In this study, we developed a scalable method for synthesizing magnetic Co$_x$Ni$_{1-x}$-Al$_2$O$_3$ nanocomposites. The synthesis is based on the co-precipitation of Co and Ni ions from an aqueous solution, coating the precipitated nanoparticles with a boehmite (AlOOH) shell via the in-situ hydrolysis of AlN powder and reduction at 850 °C in a flow of H$_2$. A combination of X-ray diffractometry (XRD) and scanning transmission electron microscopy (STEM/EDXS) showed the formation of nanocomposites containing globular Co$_x$Ni$_{1-x}$ nanoparticles (∼ 14 nm in size), homogenously distributed within the matrix composed of thin γ-Al$_2$O$_3$ nanosheets (∼ 30 nm wide and up to 3 nm thick), providing a high specific surface area (∼ 140 m$^2$ g$^{−1}$). The reduction process was studied using high-temperature XRD, hydrogen-temperature programmed reduction (H$_2$-TPR), and X-ray photoelectron spectroscopy (XPS). The magnetic properties were measured with a vibrating-sample magnetometer (VSM). The nanocomposites exhibited an excellent heating ability, exceeding 800 °C within a few minutes, even at relatively low AMF amplitudes (up to 58 mT) in a fixed-bed reactor. These results underscore the potential of Co$_x$Ni$_{1-x}$-Al$_2$O$_3$ nanocomposites for high-temperature catalytic processes, marking an advancement in magnetic catalyst support synthesis.20242024-09-03 14:01:52Članek v reviji160686sl