Promoting Effects of Au Submonolayer Shells on Structure-Designed Cu-Pd/Ir Nanospheres: Greatly Enhanced Activity and Durability for Alkaline Ethanol Electro-Oxidation

Liuxuan Luo; Cehuang Fu; Xiaohui Yan; Shuiyun Shen; Fan Yang; Yangge Guo; Fengjuan Zhu; Lijun Yang; Junliang Zhang

doi:10.1021/acsami.0c05605

Promoting Effects of Au Submonolayer Shells on Structure-Designed Cu-Pd/Ir Nanospheres: Greatly Enhanced Activity and Durability for Alkaline Ethanol Electro-Oxidation

ACS Appl Mater Interfaces. 2020 Jun 10;12(23):25961-25971. doi: 10.1021/acsami.0c05605. Epub 2020 May 26.

Authors

Liuxuan Luo¹, Cehuang Fu¹, Xiaohui Yan¹, Shuiyun Shen¹, Fan Yang¹, Yangge Guo¹, Fengjuan Zhu¹, Lijun Yang², Junliang Zhang¹

Affiliations

¹ Institute of Fuel Cells, Key Laboratory for Power Machinery and Engineering of MOE, School of Mechanical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China.
² Key Laboratory for Mesoscopic Chemistry of MOE, Jiangsu Provincial Lab for Nanotechnology, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, China.

PMID: 32395980
DOI: 10.1021/acsami.0c05605

Abstract

Rationally engineering the surface physicochemical properties of nanomaterials can improve their activity and durability for various electrocatalytic and energy conversion applications. Cu-Pd/Ir (CPI) nanospheres (NSs) anchored on N-doped porous graphene (NPG) [(CPI NSs/NPG)] have been recently demonstrated as a promising electrocatalyst for the alkaline ethanol oxidation reaction (EOR); to further enhance their electrocatalytic performance, the NPG-supported CPI NSs are coated with Au submonolayer (SML) shells (SMSs), through which their surface physicochemical properties can be tuned. CPI NSs/NPG is prepared by our previously developed method and possesses the special structures of composition-graded Cu₁Pd₁ and surface-doped Ir_0.03. The Au SMSs with designed surface coverages are formed via an electrochemical technology involving incomplete Cu underpotential deposition (UPD) and Au³⁺ galvanic replacement. A distinctive volcano-type relation between the EOR electrocatalytic activity and the Au-SMS surface coverage for CPI@Au_SML NSs/NPG is revealed, and the optimal CPI@Au_1/6ML NSs/NPG greatly surpasses commercial Pd/C and CPI NSs/NPG in electrocatalytic activity and noble metal utilization. More importantly, its electrocatalytic durability in 1 h chronoamperometric and 500-cycle potential cycling degradation tests is also significantly improved. According to detailed physicochemical characterizations, electrochemical analyses, and density functional theory calculations, the promoting effects of the Au SMS for enhancing the EOR electrocatalytic activity and durability of CPI NSs/NPG can be mainly attributed to the greatly weakened carbonaceous intermediate bonding and properly increased surface oxidation potential. This work also proposes a versatile and effective strategy to tune the surface physicochemical properties of metal-based nanomaterials via incomplete UPD and metal-cation galvanic replacement for advancing their electrocatalytic and energy conversion performance.

Keywords: electrocatalyst; ethanol electro-oxidation; gold; incomplete underpotential deposition; nanosphere; palladium; submonolayer shell.