Maintaining the stability of low Pt catalysts during prolonged operation of proton exchange membrane fuel cells (PEMFCs) remains a substantial challenge. Here, a double confinement design is presented to significantly improve the stability of intermetallic nanoparticles while maintaining their high catalytic activity toward PEMFCs. First, a carbon shell is coated on the surface of nanoparticles to form carbon confinement. Second, O