In-situ growth of carbon nanotubes for improving the performance of Co-N/C catalysts in proton exchange membrane fuel cell

•The deformed Co-N4 sites are anchored on the in-situ grown CNTs.•The deformed Co-N4 sites on CNTs can enhance O2 activation.•The CNTs effectively slows down the oxidation of carbon carrier.•The PEMFC assembled by Co-N/C-1/4.4 cathode shows a potential application value.