Multifunctional carbon nanofibers coated Co-Zn alloy nanoparticles composite for efficient energy conversion and microwave absorption

Considering the energy crisis and environment pollution, it is urgently to develop multifunctional materials to ensure the sustainable development of human society. Core-shell bimetal/carbon composites have attracted great attention in microwave absorption or electrochemical energy conversion devices, and the composite can overcome the deficient performance of pure carbon materials or pure metal materials. In this work, we proposed a simple method to prepare N-doped carbon nanofibers coated CoZn alloy nanoparticle composites (CoZn/N-CNFs) using CoZn(OH) X nanowires and melamine as precursors through pyrolysis process. The prepared CoZn/N-CNFs exhibited outstanding catalytic property for oxygen reduction reaction (ORR, half-wave potential of 0.814 V vs RHE) in alkaline solution. The CoZn/N-CNFs acted as cathode in rechargeable Zn-air batteries (ZABs) exhibited high open circuit voltage (1.33 V), large output power density (223.8 mW cm -2 ), and robust stability (87 h, 6 cycles), surpassing the commercial Pt/C-based ZABs. In addition, as an excellent performance electromagnetic wave absorber, CoZn/N-CNFs exhibited favorable impedance matching and electromagnetic wave absorption ability, which has the RLmin of -33.93 dB under a thickness of 2.1 mm, and the effective bandwidth (RL<-10 dB) of 4.56 GHz with the matching thickness of 2.2 mm. This composite is expected to be a desired metal/carbon composite for ZABs and electromagnetic absorption. This work provides a simple method for the development of multifunctional materials. 1, The CoZn/N-CNFs with nanofiber morphology have high ORR catalytic activity (half-wave potential of 0.814 V vs RHE), and the rechargeable zinc-air batteries assembled with CoZn/N-CNFs as cathodes have good discharge performance (1.33 V) and high power density (223.8 mW cm -2 ). 2, CoZn/N-CNFs have excellent electromagnetic absorption performance, with a maximum reflection loss of -33.93 dB at a thickness of 2.1 mm and an effective absorption bandwidth covering 4.56 GHz at 2.2 mm. • ThPreparation of CoZn/N-CNFs with nanofiber morphology by pyrolysis. • e synergistic effect of bimetals enhances the adsorption capacity of O 2 and electromagnetic waves. • The carbon layer has excellent electrical conductivity, while providing conductivity loss in the material. • The combination of the alloy particles and carbon layer enhance the interfacial polarization loss.