Optimization of Pd–Co–Cu and Pd–Co–Au catalysts for the oxidation of formic acid using scanning electrochemical microscopy

• Published in: Journal of alloys and compounds 2023-06, Vol.947, p.169562, Article 169562
• Main Authors: Weng, Yu-Ching, Chiang, Chieh-Lin
• Format: Article
• Language: English
• Subjects: Catalyst; Formic acid; Oxidation; Pd–Co–Au; Pd–Co–Cu; Scanning electrochemical microscopy
• ISSN: 0925-8388
• DOI: 10.1016/j.jallcom.2023.169562

This study uses scanning electrochemical microscopy (SECM) to screen ternary metal catalyst arrays for the oxidation of formic acid. Pd–Co–Au and Pd–Co–Cu ternary metal catalyst arrays are prepared using a piezoelectric dispensing system and then reduced on a glassy carbon substrate by hydrogen reduction. For the catalyst arrays, the optimal ratio of ternary alloy catalysts for the oxidation of formic acid is Pd2Co6Au2 and Pd2Co6Cu2 catalysts in Pd–Co–Au and Pd–Co–Cu ternary metal catalyst arrays, respectively. The surface morphology of Pd2Co6Au2 and Pd2Co6Cu2 catalysts is more complex and diverse than that of a pure Pd catalyst. A Pd2Co6Au2 catalyst is mainly composed of heterostructures of Au and PdCoO2, and a Pd2Co6Cu2 catalyst is mainly composed of heterostructures of CuPdO2, CuCoO2 and Co. The XPS results roughly matches with the XRD results. Cyclic voltammograms show that these two catalysts have a higher oxidation current in formic acid than that for a pure Pd catalyst. The onset potential for the oxidation of formic acid by a Pd2Co6Cu2 catalyst is lower than that for a Pd2Co6Au2 catalyst. Electrochemical impedance spectroscopy analysis shows that these catalysts exhibit pseudo inductive behavior. For an equivalent circuit, a Pd2Co6Cu2 catalyst has the smallest charge transfer resistance and removes the intermediate adsorbate at the lowest overpotential. •SECM was used to screen ternary catalyst arrays for the oxidation of formic acid.•The Pd2Co6Au2 and Pd2Co6Cu2 catalysts show excellent sensitivity.•The Pd2Co6Au2 and Pd2Co6Cu2 catalysts are composed of heterostructures.•The Pd2Co6Cu2 catalyst has the smallest charge transfer resistance and onset potential.