Electrocatalytic Activity of Pd−Co Bimetallic Mixtures for Formic Acid Oxidation Studied by Scanning Electrochemical Microscopy

Abstract

The electrochemical oxidation of formic acid was studied by the tip generation-substrate collection (TG-SC) mode of scanning electrochemical microscopy (SECM), extending the number of applications of SECM in electrocatalysis. Formic acid was generated at a Hg on Au ultramicroelectrode (UME) tip by reduction of CO(2) in a 0.1 M KHCO(3) solution saturated with this gas. The electrocatalytic activity of different Pd-Co bimetallic compositions was evaluated using a Pd-Co electrocatalyst array formed by spots deposited onto glassy carbon (GC) as a SECM substrate. The SECM tip, which generated a constant formic acid flux, was scanned above the array and the oxidation current generated when formic acid was collected by active electrocatalytic spots was displayed as a function of tip position. This generated a SECM image that showed the electrocatalytic activity of each spot. SECM screening identified Pd(50)Co(50) (Pd/Co = 50:50, atomic ratio) as a better electrocatalyst toward the formic acid oxidation than pure Pd or Pt in 0.1 M KHCO(3) solution and this result was confirmed by cyclic voltammetry. Positive feedback was observed for the most active compositions of Pd-Co which suggests fast reaction kinetics and chemical reversibility during the oxidation of formic acid to CO(2). Moreover this feedback increases the contrast between active and non-active spots in this imaging mode.

Highly active carbon-supported PdNi catalyst for formic acid electrooxidation

“…It was reported that the catalytic activity and stability of Pd were increased by addition of another precious metal into the catalyst, such as Au [22], Pt [23] or Ir [24]. Non-noble metals such as Pb [25], Sn [22,26], Co [27,28] and boron [29] have also been used as promoters for formic acid catalytic electrooxidation. However, the performances of Pd catalysts need further improvement.…”

Rapid screening of silver nanoparticles for the catalytic degradation of chlorinated pollutants in water

“…Fortunately, new electroanalytical techniques have been recently introduced to improve this screening step. In particular, the scanning electrochemical microscopy (SECM) [34,35] has demonstrated its utility as a rapid and high throughput technique in screening electrocatalyts [36] for processes A c c e p t e d M a n u s c r i p t 5 such as the oxygen reduction reaction (ORR) [37][38][39][40][41][42], methanol interference during ORR [43], chlorine evolution [44] and oxygen evolution reactions (OER) [45,46], formic acid oxidation (FAOR) [47,48] and methanol oxidation reactions (MOR) [48].…”

Rapid Characterization of Hydrogen Evolution Electrocatalyst Spot Arrays by the Pulsed-Potential Substrate Generation/Tip Collection Mode of Scanning Electrochemical Microscopy

“…Both the feedback mode [4] and generation/collection modes [5,6] offer significant advantages for the quantitative detection of reaction intermediates and measurements of the electrontransfer kinetics. Electrocatalyst screening techniques based on SECM show incomparable versatility in the comparison and selection of electrocatalysts and photoelectrocatalysts [5,[7][8][9][10]. In order to probe more catalytic spots during a screening experiment, the distance between spots should be controlled as small as possible.…”