Metal nanoparticles support materials play a crucial role in many fields, including energy conversion/storage, catalysis and photochemistry. Here, the exsolution is reported as an in situ method to fabricate metal nanoparticles supported on perovskite (La_0.52Ca_0.28Ni_0.06Ti_0.94O₃) powder and fiber materials. Significantly decreased polarisation resistance can be achieved by applying electrochemical switching within 3 min on the fiber electrode fuel cell to facilitate the exsolution. The fuel cell activated by electrochemical switching under wet hydrogen shows a promising performance with a maximum output power density of about 380 mW cm⁻² at 900 °C in hydrogen. The phase-field model shows that the exsolution under extreme low oxygen partial pressure induced by electrochemical switching performs faster nucleation than the chemical-reduced case. This work provides a further understanding of electrochemically driven exsolution with fiber structure platform and simulation with phase-field models.