Sputtered Nanoporous PtNi Thin Film Cathodes with Improved Thermal Stability for Low Temperature Solid Oxide Fuel Cells

•Alloying Pt with Ni had hindered the thermal agglomeration by constraining grain growth.•The porosity of PtNi thin film cathode was preserved under operating at 450°C for 48hours.•Improved long-term thermal stability of cell using PtNi alloy cathode over pure Pt cathode.•Alloying of Ni with Pt also improved the cathode oxygen reduction reaction kinetics. Nanoporous PtNi alloy thin film was demonstrated to effectively improve the thermal stability of cathode under high temperature fuel cell operation. The grain growth, which indicates the agglomeration of the nanoparticles, were constrained, as observed by comparing the surface morphologies and grain sizes in bulk of film between pure Pt and PtNi alloy cathodes. The constrained grain growth by alloying with Ni maintained the porosity in bulk of cathode film for sufficient cathode oxygen diffusion and adsorption/dissociation processes. Fuel cell using Pt67-Ni33 cathode better maintained the output current density than the cell using pure Pt cathode by 26% after 48hours of continuous operation.