Self-templated carbon enhancing catalytic effect of ZrO2 nanoparticles on the excellent dehydrogenation kinetics of MgH2

Abstract

Development of highly effective carbon-based multifunctional catalysts for improvement of light metal hydrogen storage materials is of great significance. Herein, a novel self-template method is proposed to synthesize carbon-encapsulated ZrO2 (5–10 nm) nanoparticles (ZrO2/C). It is found that carbon could highly improve the catalysis of ZrO2 towards MgH2 than that of ZrO2 without C. Specifically, MgH2–ZrO2/C composite remarkably reduces the onset operating temperature to 208 °C, much lower than that of MgH2–ZrO2 (248 °C) and undoped MgH2 (309 °C). Furthermore, DFT calculations were applied to elucidate the detailed catalysis mechanism of C in ZrO2/C. The results demonstrated that for the MgH2–ZrO2/C sample, Zr atoms can weaken the Mg–H bonding strength. When Mg–H bond is broken, C substrates easily “pull” the electrons from H− atoms and eliminate the bound effect of Zr on H−, thus leading to the lower hydrogen desorption energy. This work provides clear evidence to understand the synergistic catalysis of ZrO2 and C, and offers a new strategy to synthesize carbon-encapsulated metal oxides with efficient catalysis towards light metal hydrogen storage materials.