Comparative Study of Platinum Deposition Methods on Ni Support for Enhanced Formic Acid Electrooxidation

Reducing dependency on fossil fuels and developing efficient renewable energy sources are still important issues for sustainable development. Fuel cells powered by small organic molecules, such as formic acid, have attracted significant interest due to their potential for clean energy production. Platinum (Pt) is recognized as a highly effective catalyst for formic acid electrooxidation (FAO), but its high cost, scarcity, and susceptibility to CO poisoning prevent widespread use. To address these issues, we have investigated two different methods for depositing Pt onto nickel (Ni) substrate: electrochemical deposition and galvanic displacement, and compared their effects on FAO activity. The first method involved the electrochemical deposition of thin Pt film onto Ni (Pt@Ni) followed by controlled thermal treatment. The second method involved spontaneous galvanic displacement, in which a drop of hexachloroplatinic acid was applied to a Ni substrate, resulting in an ultra thin Pt@Ni film. As in the first method, a similar annealing treatment optimized the catalyst's surface morphology and stability, achieving better activity with minimal Pt usage. Catalysts were characterized using cyclic voltammetry, CO monolayer oxidation, and atomic force microscopy (AFM) to evaluate the effects of the deposition method and annealing conditions. The activity of the Pt@Ni catalyst obtained by the electrochemical deposition method is highest at 500 oC compared to the as prepared and catalyst annealed to 300 oC. In the case of electrochemical deposition, the annealing process induces surface reconstruction and Ni migration to the surface, thus enabling the bifunctional effect and improving catalytic performance by reducing CO poisoning at low potentials. In the case of the spontaneous galvanic displacement method, the activity of the Pt@Ni catalysts annealed to 300 oC is the highest due to the excessive amount of Ni present at the surface of the catalyst annealed to 500 oC. This result was confirmed by the CO stripping experiment. The results demonstrated that the choice of deposition method and thermal treatment substantially impacts catalytic performance. The electrochemical deposition approach showed advantages in surface reconstruction, while the galvanic displacement method achieved higher Pt utilization efficiency. This comparative study emphasizes the important role of synthesis processes, substrate characteristics and thermal treatment in developing cost-effective, high-performance FAO catalysts.