In situ redox growth of mesoporous Pd-Cu₂O nanoheterostructures for improved glucose oxidation electrocatalysis

Interfaces of metal-oxide heterostructured electrocatalyst are critical to their catalytic activities due to the significant interfacial effects. However, there are still obscurities in the essence of interfacial effects caused by crystalline defects and mismatch of electronic structure at metal-oxide nanojunctions. To deeply understand the interfacial effects, we engineered crystalline-defect Pd-Cu₂O interfaces through non-epitaxial growth by a facile redox route. The Pd-Cu₂O nanoheterostructures exhibit much higher electrocatalytic activity toward glucose oxidation than their single counterparts and their physical mixture, which makes it have a promising potential for practical application of glucose biosensors. Experimental study and density functional theory (DFT) calculations demonstrated that the interfacial electron accumulation and the shifting up of d bands center of Cu-Pd toward the Fermi level were responsible for excellent electrocatalytic activity. Further study found that Pd(3 1 0) facets exert a strong metal-oxide interface interaction with Cu₂O(1 1 1) facets due to their lattice mismatch. This leads to the sinking of O atoms and protruding of Cu atoms of Cu₂O, and the Pd crystalline defects, further resulting in electron accumulation at the interface and the shifting up of d bands center of Cu-Pd, which is different from previously reported charge transfer between the interfaces. Our findings could contribute to design and development of advanced metal-oxide heterostructured electrocatalysts.