Methanol gas detection of electrospun CeO2 nanofibers by regulating Ce3+/ Ce4+ mole ratio via Pd doping

•Pd-doped CeO2 nanofibers were prepared by a simple electrospinning method.•The Pd doping can affect the Ce3+/Ce4+ ratio and thus the sensing performance.•The nanofiber sensor presents enhanced methanol-sensing performance.•The sensing mechanism can be described by Ce3+/Ce4+ induced oxygen vacancies.