Synthesis of star-like MnO2-CeO2/CNT composite as an efficient cathode catalyst applied in lithium-oxygen batteries

Synergistic enhancement of oxygen vacancy enrichment and morphology regulation in CeO2-NiCo2O4 heterostructure catalysts for high-performance cathodes in direct borohydride-hydrogen peroxide fuel cells

Hydrogen peroxide (H2O2) emerges as a viable oxidant for fuel cells, necessitating the development of an efficient and cost-effective electrocatalyst for the hydrogen peroxide reduction reaction (HPRR). In this study, we synthesized a self-supporting, highly active HPRR electrocatalyst comprising two morphologically distinct components: CeO2-NiCo2O4 nanowires and CeO2-NiCo2O4 metal organic framework derivatives, via a two-step hydrothermal process followed by air calcination. X-ray diffraction and transmission electron microscopy analysis confirmed the presence of CeO2 and NiCo2O4, revealing the amalgamated interface between them. CeO2 exhibits multifunctionality in regulating the surface electronic configuration of NiCo2O4, fostering synergistic connections, and introducing oxygen deficiencies to enhance the catalytic efficacy in HPRR. Electrochemical measurements demonstrate a reduction current density of 789.9 mA·cm-2 at -0.8 V vs. Ag/AgCl. The assembly of direct borohydride-hydrogen peroxide fuel cell (DBHPFC) exhibits a peak power density of 45.2 mW·cm-2, demonstrating durable stability over a continuous operation period of 120 h. This investigation providing evidence that the fabrication of heterostructured catalysts based on CeO2 for HPRR is a viable approach for the development of high-efficiency electrocatalysts in fuel cell technology.

Composite NiCo2 O4 @CeO2 Microsphere as Cathode Catalyst for High-Performance Lithium-Oxygen Battery

The large overpotential and poor cycle stability caused by inactive redox reactions are tough challenges for lithium-oxygen batteries (LOBs). Here, a composite microsphere material comprising NiCo₂ O₄ @CeO₂ is synthesized via a hydrothermal approach followed by an annealing processing, which is acted as a high performance electrocatalyst for LOBs. The unique microstructured catalyst can provide enough catalytic surface to facilitate the barrier-free transport of oxygen as well as lithium ions. In addition, the special microsphere and porous nanoneedles structure can effectively accelerate electrolyte penetration and the reversible formation and decomposition process of Li₂ O₂ , while the introduction of CeO₂ can increase oxygen vacancies and optimize the electronic structure of NiCo₂ O₄ , thereby enhancing the electron transport of the whole electrode. This kind of catalytic cathode material can effectively reduce the overpotential to only 1.07 V with remarkable cycling stability of 400 loops under 500 mA g^-1 . Based on the density functional theory calculations, the origin of the enhanced electrochemical performance of NiCo₂ O₄ @CeO₂ is clarified from the perspective of electronic structure and reaction kinetics. This work demonstrates the high efficiency of NiCo₂ O₄ @CeO₂ as an electrocatalyst and confirms the contribution of the current design concept to the development of LOBs cathode materials.