It is a challenge to improve the long-term durability of Pd-based electrocatalysts for oxygen reduction reaction (ORR) in fuel cells. Herein, Pd/CeO2-C-T (T=800, 900 and 1000℃) hybrid catalysts with metal-support interaction are prepared from Ce-based metal organic framework (Ce-MOF) precursor. Abundant tiny CeO2 nanoclusters are produced to form nanorod structures with uniformly distributed carbon through a calcination process. Meanwhile, both carbon and CeO2 nanoclusters have good contact with the following deposited surfactant-free Pd nanoclusters. Benefited from the large specific surface area, good conductivity and structure integrity, Pd/CeO2-C-900 exhibits the best electrocatalytic ORR performance: onset potential of 0.968 V and half-wave potential of 0.857 V, outperforming those obtained on Pd/C counterpart. In addition, the half-wave potential only shifts 7 mV after 6000 cycles of accelerated durability testing, demonstrating robust durability.
Fe 0 -Fe 3 O 4 nanoparticles and cerium dioxide hollow spheres as efficient heterogeneous electro-Fenton reagents were rationally designed to be embedded in porous carbon derived from skimmed cotton for the electrocatalytic degradation of ceftriaxone sodium. Skimmed cotton porous carbon material has a hollow tubular structure, and cerium dioxide is dispersed on the surface of the carbon material in a hollow sphere structure of uniform size. Fe 0 -Fe 3 O 4 nanoparticles were wrapped in irregular particle shapes on the surface of cerium dioxide hollow spheres, and the remaining part was laid flat on the surface of porous carbon material. The as-synthesized Fe 0 -Fe 3 O 4 /CeO 2 /C showed excellent degradation efficiency of 95.59 % for ceftriaxone sodium within 120 mins and obtained a COD removal rate of 95.21 % at 240 mins. The zero-valent iron as a reducing agent effectively accelerated the Fe 3+ /Fe 2+ cycle, allowing the composites to exhibit higher catalytic activity and further reducing the possibility of secondary contamination. Moreover, the existence of cerium dioxide further promoted the redox cycle of Ce 4+ /Ce 3+ and accelerated the electron transfer in the interface of the catalyst. The synergistic effect of iron and cerium greatly facilitated the production of hydroxyl radicals and increased the yield of hydroxyl radicals in the reaction system.
MgH 2 exhibits significant potential as promising candidates for next-generation hydrogen storage solutions, owing to excellent hydrogen storage capacity. However, its high thermodynamic stability and kinetic barriers result in sluggish dehydrogenation kinetics and high dehydrogenation temperatures. Herein, oxygen vacancy (O V )-rich CeO 2 @C effectively weakens the Mg–H bond energy, which is manifested as the elongation of the Mg–H bond. Moreover, the O V -rich CeO 2 @C reacts with H 2 to form CeH 2.73 , which enhances hydrogen diffusion within the Mg/MgH 2 system. Meanwhile, the formation of CeH 2.73 promotes the formation of O V within the MgH 2 -CeO 2 @C, further facilitating the dehydrogenation of MgH 2 . Thereby, the synergistic effect of the O V -rich CeO 2 @C and CeH 2.73 lower the dehydrogenation temperature of MgH 2 and enhance kinetic performance. The MgH 2 -CeO 2 @C-3h behaves the most optimal dehydrogenation performance, achieving a release of 4.88 wt% H 2 within 10 min at 350 ℃. The initial dehydrogenation temperature of the MgH 2 -CeO 2 @C-3h is reduced to 274 ℃, and the dehydrogenation activation energy ( E a ) is lowered to 99.13 kJ mol –1 , compared to 327 ℃ and 160.7 kJ mol –1 for pristine MgH 2 . This work provides new insights into designing O V -rich metal oxide catalysts for MgH 2 .
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