From Moldy Orange Waste to Natural Reductant and Catalyst Support: Active Palladium/Biomass-Derived Carbonaceous Hybrids for Promoted Methanol Electro-Oxidation

Facile, green, and low-cost synthesis of advanced electrocatalysts is widely considered an urgent issue and a current challenge for clean energy conversion. Here, we report the green fabrication of a new Pd/C(OJ) hybrid, using orange juice (OJ) simultaneously as a natural reductant and a support precursor, for the methanol oxidation reaction (MOR) in alkaline media. The juice extracted from discarded moldy oranges is capable of reducing the [PdCl₄]²⁻ species into metallic Pd through a simple hydrothermal reaction, and then becomes the nitrogen-doped carbonaceous support after pyrolysis for active catalyst loading. In the synthesized Pd/C(OJ) hybrid, Pd nanoparticles with a mean size of 7.3 nm are highly dispersed throughout the support, providing a larger electrochemically active surface area than commercial Pd/C. As a result, the Pd/C(OJ) electrocatalyst exhibits 1.78 times the mass activity of the latter for the MOR. The preferable performance durability of Pd/C(OJ) is also verified by using cyclic voltammetry and simulative startup−shutdown measurements.