Composition-Graded Cu-Pd Nanospheres with Ir-Doped Surfaces on N-Doped Porous Graphene for Highly Efficient Ethanol Electro-Oxidation in Alkaline Media

Tuning the compositions and structures of Pd-based nanomaterials and their supports has shown great potentials in facilitating the sluggish ethanol oxidation reaction (EOR) in alkaline direct ethanol fuel cells. Accordingly, a facile solvothermal method involving Cu and Pd composition migrations is developed in this study, to synthesize highly uniform and small-sized nanospheres (NSs) possessing the special structures of composition-graded (CG) Cu1Pd1 and surface-doped (SD) Ir-0.03 which are evenly anchored onto N-doped porous graphene (NPG) as a high-performance EOR electrocatalyst ((Cu1Pd1)-Cu-CG/Ir-SD(0.03) NSs/NPG). Comprehensive physicochemical characterizations, electrochemical analyses, and first-principles calculations reveal that, benefiting from the NPG-imparted mass-transfer and oxygen-reduction effects, the CG-SD structural and size morphology effects of the NS, as well as the Cu- and Ir-induced bifunctional, geometric, and ligand effects, (Cu1Pd1)-Cu-CG/Ir-SD(0.03) NSs/NPG exhibits not only ultrahigh electrocatalytic activity and highly efficient noble-metal (NM) utilization, showing 7105 and 6685 mA mg(-1) in Pd- and NM-mass-specific activity (MSA), respectively, which are 15.8 and 14.9 times those of commercial Pd/C, but also satisfactory electrocatalytic durability, retaining respective 28.1- and 19.2-fold enhancements in Pd-MSA compared to the commercial Pd/C, after 1 h chronoamperometric and 500-cycle potential cycling degradation tests. This study not only provides an effective and versatile synthetic strategy to prepare the NM-efficient metal-based nanomaterials with the special CG and SD structures for various electrocatalytic and energy-conversion applications, but also proposes some insights into the composition- and structure-function relations in EOR electrocatalytic mechanism for rationally designing highly active and durable EOR electrocatalysts.