In the pursuit of inexpensive and efficient oxygen reduction catalysts, Fe–N–C catalysts have garnered significant attention as a viable alternative to scarce platinum-based materials. Nevertheless, the intricate interaction between the carbon matrix and Fe active sites, along with the mechanism by which such synergies modulate catalytic activity, remains elusive. Herein, a programmed temperature pyrolysis strategy is developed to optimize both the carbon matrix properties and coordination environments of Fe sites. Systematic characterizations uncover the correlations between key parameters of Fe sites (the oxidation state, coordination number, and density of state), as well as the carbon matrix (the functional groups, nitrogen species and content, and the degree of graphitization), with the resultant catalytic activity. The optimized catalyst exhibits a high half-wave potential of 0.935 V and good stability, and the assembled zinc–air battery delivers a high peak power density and long-term cycling durability. Theoretical calculations reveal that Fe–N₄ coordination more effectively reduces the energy barrier for *OH release compared to Fe–N₃ coordination. Additionally, adjacent graphitic nitrogen species further lower the energy barrier of the rate-determining step, thereby accelerating oxygen reduction kinetics. This work highlights the critical role of the carbon support and Fe site properties in synergistically boosting the catalytic performance.

Bismuth-based perovskites are considered to be promising candidates to substitute the toxic lead-based perovskite in optoelectronics due to their excellent optoelectronic properties, high environmental friendliness, and (moisture, light, and heat) stability. However, there are still few reports about high performance bismuth-based perovskite ultraviolet photodetectors, and is more lacking in ultraviolet imaging demonstration. Herein, we reported a self-powered NiO_x/Cs₃Bi₂Br₉ heterojunction photodetector with excellent photodetection performance by electrochemical depositing NiO_x as the hole transport layer. The optimized NiO_x/Cs₃Bi₂Br₉ heterojunction photodetector exhibits excellent ultraviolet detection performance with a fast response speed of 3.04/4.65 ms, wide linear dynamic range of 116.6 dB, decent responsivity of 4.33 mA·W⁻¹ at 0 V bias, and high detectivity of 1.3 × 10¹¹ jones. The outstanding performance of the optimized NiO_x/Cs₃Bi₂Br₉ heterojunction photodetector is enough to meet the high-quality ultraviolet imaging. Therefore, we further integrated the optimized NiO_x/Cs₃Bi₂Br₉ heterojunction photodetector to the transmission mode ultraviolet multispectral imaging system, achieving admirable imaging results at weak light condition. This work will play a positive role in promoting the development of bismuth-based ultraviolet photodetection and ultraviolet multispectral imaging.

With the increased demand from the storage of renewable energy sources, some safe and inexpensive energy storage technologies instead of Li-ion batteries become urgently needed. Therefore, K-ion batteries (KIBs) have attracted much attention and evolved significant development because of the low price, safety, and similar property compared with Li-ion batteries. Due to the high reversibility, stability, and low potential plateau, graphite becomes a current research focus and is regarded as one of the most promising KIB’s anode materials. In this review, we mainly discuss the electrochemical reaction mechanism of graphite during potassiation-depotassiation process and analyze the effects of electrode/electrolyte interface on graphite for K-ion storage. Besides, we summarize several kinds of methods to improve the performance of graphite for KIBs, including the design of graphite structure, selection of appropriate binder, solvent chemistry, and salt chemistry. Meanwhile, a concept of “relative energy density” is raised, which can be more accurate to evaluate the genuine electrochemical performance of graphite anode involving the specific capacity and potential. In addition, we also summarize the considerable challenges to current graphite anode in KIBs and we believe our work will offer alterative solutions to further explore high-performance graphite anode of K-ion storage.