Symbiotic CeH2.73/CeO2 catalyst: A novel hydrogen pump

•Symbiotic CeH2.73/CeO2 nanoparticles are synthesized upon the amorphous Mg alloy.•Dehydrogenation temperature of MgH2 is significantly reduced.•Catalysis arises from the interface of the symbiotic CeH2.73/CeO2 nanoparticles.•The catalysis is confirmed via in situ HRTEM and theoretical calculations.•Materials fabrication is suitable for large-scale production.

Using additives/catalysts to destabilize hydrides of high hydrogen storage density, e.g. MgH2 with 7.6 wt%-H and desorption temperature as high as 300–400 °C, is one of the most important strategies to overcome the hurdle of applying hydrogen storage materials in technologies related to hydrogen energy. Despite tremendous efforts, to develop additives/catalysts with high catalytic activity and easy doping remains a great challenge. Here, we report a simple method to induce a novel symbiotic CeH2.73/CeO2 catalyst in Mg-based hydrides, which is capable of massive fabrication. More importantly, we reveal a spontaneous hydrogen release effect at the CeH2.73/CeO2 interface, which leads to dramatic increase of catalysis than either sole CeH2.73 or CeO2 catalyst. Maximum hydrogen desorption temperature reduction of MgH2 could reach down to ~210 °C as molar ratio of CeH2.73 to CeO2 was 1:1. The dynamic boundary evolution during hydrogen desorption was observed in the symbiotic CeH2.73/CeO2 at atomic resolution using in situ High-Resolution Transmission Electron Microscope (HRTEM). Combining the ab-initio calculations, which show significant reduction of the formation energy of VH (hydrogen vacancy) in the CeH2.73/CeO2 boundary region in comparison to those in the bulk MgH2 and CeH2.73, we demonstrate that the outstanding catalytic activity can be attributed to the spontaneous hydrogen release effect at the CeH2.73/CeO2 interface.

Graphical abstractSymbiotic CeH2.73/CeO2 nanoparticles have been in situ generated in the Mg-based hydrides via hydrogenation and oxidation treatments upon the amorphous Mg alloy. The in situ TEM/HRTEM observations during hydrogen desorption and first principle calculations demonstrate that the unusual catalytic activity arises from the boundary “hydrogen pump” effect in the interface region of the symbiotic CeH2.73/CeO2.Figure optionsDownload full-size imageDownload as PowerPoint slide