Designing a highly efficient non-precious based oxygen reduction reaction (ORR) electrocatalyst is critical for the commercialization of various sustainable energy storage and conversion devices such as metal-air batteries and fuel cells. Herein, we report a convenient strategy to synthesis Fe₃O₄ embedded in N doped hollow carbon sphere (NHCS) for ORR. What's interesting is that the carbon microsphere is composed of two-dimensional (2D) nanoplate that could provide more exposed active sites. The usage of solid ZnO nanowires as zinc source is crucial to obtain this structure. The Fe₃O₄@NHCS-2 exhibits better catalytic activity and durability than the commercial Pt/C catalyst. Moreover, it further displays high-performance of Zn-air batteries as a cathode electrocatalyst with a high-power density of 133 mW·cm^-2 and high specific capacity of 701 mA·h·g^-1. The special hollow structure composed 2D nanoplate, high surface area, as well as synergistic effect between the high active Fe₃O₄ nanoparticles and N-doped matrix endows this outstanding catalytic activity. The work presented here can be easily extended to prepare metal compounds decorated carbon nanomaterials with special structure for a broad range of energy storage and conversion devices.

To promote commercialization of perovskite solar cells (PSCs), low-temperature processed electron transport layer (ETL) with high carrier mobility still needs to be further developed. Here, we reported two-dimensional (2D) tin disulfide (SnS₂) nanosheets as ETL in PSCs for the first time. The morphologies of the 2D SnS₂ material can be easy controlled by the in situ synthesized method on the conductive fluorine-doped tin oxide (FTO) substrate. We achieved a champion power conversion efficiency (PCE) of 13.63%, with the short-circuit current density (J_SC) of 23.70 mA/cm², open-circuit voltage (V_OC) of 0.95 V, and fill factor (FF) of 0.61. The high J_SC of PSCs results from effective electron collection of the 2D SnS₂ nanosheets from perovskite layer and fast electron transport to the FTO. The low V_OC and FF are the results of the lower conduction band of 2D SnS₂ (4.23 eV) than that of TiO₂ (4.0 eV). These results demonstrate that 2D material is a promising candidate for ETL in PSCs.