Pd Nanoparticles-Decorated Three-Dimensional Hierarchical Structure SnO₂/rGO@Ni Foam Self-Supporting Electrode for Direct Borohydride-Hydrogen Peroxide Fuel Cells

Developing efficient bifunctional electrocatalysts is crucial for improving the performance of direct borohydride-hydrogen peroxide fuel cells (DBHPFCs). Here, we present a rational design of a three-dimensional (3D) hierarchically structured Pd/SnO 2 /rGO@Ni foam (Pd/SnO 2 /rGO@NF) self-supporting electrocatalyst. The fabrication process begins with the coating of two-dimensional rGO nanosheets onto the surface of the nickel foam (NF) skeleton through a simple impregnation method. Subsequently, SnO 2 nanorods are vertically grown via a hydrothermal method, followed by the uniform dispersion of Pd nanoparticles using a chemical reduction technique, thus forming the hierarchical Pd/SnO 2 /rGO@NF electrocatalyst. The Pd/SnO 2 /rGO@NF electrocatalyst demonstrates excellent bifunctional performance, facilitating both hydrogen peroxide (H 2 O 2 ) electroreduction in acidic and basic media and sodium borohydride (NaBH 4 ) electrooxidation in basic media. The Pd/SnO 2 /rGO@NF electrocatalyst achieves a remarkable H 2 O 2 reduction current density of 749 mA cm –2 at −1.5 V in acidic media (408 mA cm –2 at 0.4 V in basic media) and a NaBH 4 oxidation current density of 450 mA cm –2 at 0.8 V in basic media. When implemented in a DBHPFC, the Pd/SnO 2 /rGO@NF electrocatalyst shows a peak power density of 116.5 mW cm –2 . The exceptional electrochemical performances of this optimal electrocatalyst are primarily attributed to its distinct hierarchical structure and the efficient application of Pd nanocomposites. These results suggest that the 3D hierarchical structured Pd/SnO 2 /rGO@NF self-supporting electrocatalyst may serve as a potential candidate for use as a bifunctional electrocatalyst.