Understanding the origin of the catalytic activity for the development of efficient catalysts is critical yet challenging. Herein, we report a simple strategy for the synthesis of chromium nitride nanoparticles (CrNNPs) encapsulated into hollow chromium–nitrogen–carbon capsules ([email protected]–Cr–N_x–C). The [email protected]–Cr–N_x–C demonstrated excellent electrocatalytic activity for the oxygen reduction reaction (ORR) in acidic solutions. When applied as a cathode material in a proton-exchange membrane fuel cell (PEMFC), the [email protected]–Cr–N_x–C achieved outstanding initial performance, which is better than that of the PEMFC with H–Cr–N_x–C cathode material. The [email protected]–Cr–N_x–C cathode also showed good stability over 110 h of operation. These results demonstrated that the coexistence of atomically dispersed CrN_x sites and sufficient CrNNPs is essential for excellent PEMFC performances. Density functional theory (DFT) studies further corroborated that CrNNPs can boost the ORR activity of H–Cr–N_x–C. This finding opens a new avenue for the fabrication of low-cost, highly active, and durable ORR catalysts for PEMFC and other applications.

了解用于开发高效催化剂的催化活性的来源是至关重要但具有挑战性的。在这里，我们报告了一种简单的策略，用于合成封装在空心铬-氮-碳胶囊（[电子邮件保护] -Cr-N _x -C）中的氮化铬纳米粒子（CrNNPs ）。[受电子邮件保护] –Cr– _Nx –C对酸性溶液中的氧还原反应（ORR）具有出色的电催化活性。当作为质子交换膜燃料电池（PEMFC）的阴极材料使用时，[受电子邮件保护] –Cr–N _x –C实现了出色的初始性能，这优于具有H–Cr–N _x的PEMFC。-C阴极材料。[受电子邮件保护] –Cr–N _x-C阴极在运行110小时后也显示出良好的稳定性。这些结果表明，原子分散的CrN _x位点和足够的CrNNPs共存对于出色的PEMFC性能至关重要。密度泛函理论（DFT）研究进一步证实了CrNNPs可以提高H–Cr–N _x –C的ORR活性。该发现为PEMFC和其他应用的低成本，高活性和耐用的ORR催化剂的制造开辟了新途径。