Due to the high theoretical capacity and electrode potential, Prussian blue is regarded as promising cathode material for potassium ion batteries. However, inferior structural stability, poor electronic conductivity, and ambiguous energy storage mechanism have limited the application of Prussian blue materials. Herein, a highly stable Prussian blue-polypyrrole (PB-PPY) composite has been prepared by a facile one-step method. PB-PPY displays higher discharging capacity, better rate capacity, and longer cycling lifespan than that of pure Prussian blue in potassium ion batteries. The superior electrochemical performance can be attributed to the unique synthesis strategy to reduce the content of vacancies and crystal water in Prussian blue and enhance the conductivity. Furthermore, partial K ions have been evidenced that could remain in the Prussian blue framework, which contributes the long-term cycling stability. The K ions in the framework play the role of “pillars” to support the framework of Prussian blue and relieve the structural stress during the intercalation and de-intercalation of K ions. This work will reveal a new energy storage mechanism of Prussian blue and promote the design of high stability Prussian blue in the future.

N₂ electroreduction reaction (NRR) offers a feasible and promising alternative for NH₃ production by using clean energy sources. However, it is still obstructed by the pretty low NH₃ yield rate and Faradaic efficiency (FE) primarily due to the undesired competing hydrogen evolution reaction and the extremely stable N≡N bond. Herein, bismuth nanoparticles were successfully embedded in N and P co-doped carbon nanoflakes (Bi/NPC) by high-temperature pyrolyzation of Bi-zeolitic imidazole frameworks (ZIF) followed by phosphorization, and used as a high-efficiency catalyst toward N₂ electroreduction to NH₃. In 0.1 M KHCO₃ electrolyte, Bi/NPC exhibits excellent NRR performances, including a high NH₃ yield rate of 3.12 µg·h⁻¹·cm⁻² (−0.6 V vs. reversible hydrogen electrode (RHE)), an outstanding FE of 13.58% (−0.4 V vs. RHE), and a remarkable stability up to 36 h under ambient conditions. This outstanding NRR catalytic activity is mainly attributed to the intrinsic electrocatalytic NRR activity combined with the inert hydrogen evolution reaction (HER) activity of Bi, the adsorption and activation of N₂ facilitated by N dopants, as well as the superior conductivity and the large specific surface area of the two-dimensional layered carbon matrix. Notably, the hydrogen source provided by P dopant promotes the hydrogenation of the adsorbed N, which further boosts the NRR performance in alkaline electrolyte. The ultralong durability of Bi/NPC is attributed to the highly dispersed bismuth catalytic active centers confined in the skeleton of N and P co-doped carbon nanoflakes, which inhibits the agglomeration of bismuth centers. This work presents a novel avenue for designation and fabrication of high-performance Bi-based electrocatalysts for NRR.