Palladium Nanoparticles with Surface Enrichment of Palladium Oxide Species Immobilized on the Aniline-Functionalized Graphene As an Advanced Electrocatalyst of Ethanol Oxidation

A new electrocatalyst (denoted as Pd-PdOx/GS-NH2) was fabricated by anchoring Pd nanoparticles with surface enrichment of palladium oxide species (PdOx, including palladium oxides and palladium hydrous oxides) on the aniline-functionalized graphene (GS-NH2) in this work. The GS-NH2 with tunable contents of aniline groups was prepared by a diazo reaction under facile reaction conditions. Then, the surface-clean Pd nanoparticles were decorated on the surface of GS-NH2 by a facile and nonsurfactant approach. Afterward, the palladium oxide species was introduced on the surface of Pd nanoparticles by oxidation treatment in a short period of time. As a catalyst toward the ethanol electrooxidation reaction (EOR), Pd-PdOx/GS-NH2 displays the introduction of appropriate aniline groups and an oxidation treatment with a codependent electrochemical behavior of EOR, mainly owing to the synergy of aniline groups and PdOx. The introduction of aniline groups on the surface of graphene benefits the formation of small size and uniform distribution for nanoparticles and suppresses the dissolution of Pd during electrochemical tests, due to the strong interaction between aniline groups and nanoparticles. However, the excess contents of aniline groups can reduce electrical conductivity of the catalysts, and the optimal mass ratio of 1,4-diaminobenzene to graphene is 1:3. The generated PdOx can strikingly facilitate the removal of COads-like intermediates and elimination of poisoning species during the EOR process, thereby reducing the degradation rate of the catalyst. Therefore, the Pd-PdOx/GS-NH2 possesses superb EOR performance with robust durability and is a kind of great potential anode catalyst for direct ethanol fuel cells. This work also affords a new thought for rationally designing high-performance catalysts.