Insight into electrocatalytic stability of low loading Pt-Bi/GC and Pt/GC clusters in formic acid oxidation

Abstract

Formic acid oxidation was examined on platinumbismuth deposits on glassy carbon substrate prepared by twostep process, i.e., electrochemical deposition of Bi followed by electrochemical deposition of Pt as described in our previous article (J Electrochem Soc 161:H547-H554, 2014). Upon treatment of as-prepared clusters by slow anodic sweep, bimetallic structure consisting of Bi core occluded by Pt and Bi-oxide was obtained and exhibited significant activity and exceptional stability in HCOOH oxidation. In order to explain such electrocatalytic stability, in this work, the electrochemical properties of Pt@Bi/GC catalyst were investigated applying same protocols in supporting electrolyte with or without HCOOH and compared with Pt/GC. The protocols comprised potentiodynamic, quasisteady-state, and chronoamperometric measurements combined with the surface characterization by CO ads stripping voltammetry. Application of potential cycling at Pt@Bi/GC electrode in supporting electrolyte containing HCOOH leads to minor change in surface morphology, mildly leaching of Bi from the electrode surface, and negligible decrease in activity. On the other hand, significant Bi dissolution and considerable decrease in activity are the effects of the same treatment without HCOOH. Contrary to Pt@Bi/GC, Pt/GC electrodes subjected to the same protocols exhibit completely opposite properties being more stabile during potential cycling without HCOOH than in the presence of this acid. Exceptional stability in formic acid oxidation of Pt@Bi/GC catalyst is thus most probably the result of the combination of predominant dehydrogenation path of the reaction, suppressed Bi leaching, and compensation of dissolved Bi from the core as its source due to which surface morphology endured minor changes.

Aqueous Synthesis of Highly Dispersed Pt2Bi Alloy Nanoplatelets for Dimethyl Ether Electro-Oxidation

“…The reason has been postulated to be slower leaching Bi metal from the substructure of the catalyst. Support for this mechanism is provided by recent work involving electrochemical reduction of Pt directly onto Bi metal. , …”

“…Support for this mechanism is provided by recent work involving electrochemical reduction of Pt directly onto Bi metal. 11,12 Despite these advances in electrocatalyst development, practical application of Bi in operating fuel cells requires their dispersion in the NP form to maximize the surface-tovolume ratio of the active precious metal. Unfortunately, existing methods of Bi metal and Bi alloy NP syntheses employ toxic organic solvents, expensive organic precursors, or dangerous reducing agents such as hydrozine and lithium.…”

Irreversibly Adsorbed Tri-metallic PtBiPd/C Electrocatalyst for the Efficient Formic Acid Oxidation Reaction

“…Bismuth (Bi) is considered the most efficient modifier of the Pt catalyst for the HCOOH oxidation because of its third-body effect and electronic effect on the Pt surface [11][12][13][14]. Herrero et al reported that Bi-modified Pt exhibited improved electrocatalytic activity and stability because of the synergistic effects of Bi in cleaving the O-H bond and Pt causing C-H bond scission [14].…”

“…In addition, Bi can promote the direct pathway (dehydrogenation) of HCOOH, which can reduce the extent of CO poisoning of Pt. On the other hand, Bi can be easily leached out from the electrode surface or oxidized to Bi 2 O 3 at poten-tials over 0.8 V (vs. Ag/AgCl) in acid solution, which means that the Bi-modified Pt catalyst is so unstable when used at high potentials [12,15]. Recently, Ptbased tri-metal electrocatalysts, including PtPdAu [16], PtCuBi [17], and PtRuSn [18], have been studied widely to overcome such problems.…”

In–situ Synthesizing and Optimizing the Surface Structure of Nanoporous PtBi Electrocatalysts for Formic Acid Electro–oxidation

“…In view of taking the respective advantages of platinum and bismuth, varieties of PtBi nanocatalysts have been prepared to promote the catalysts' activity towards FA oxidation. [11][12][13][14] However, as bismuth species easily dissolve at higher potential, [15][16][17] PtBi electrocatalysts mainly performed on a narrow potential range limiting to 0.8 V (Potentials given in this paper were all versus reversible hydrogen electrode, RHE.). However, with that method, the dehydration process is interrupted during FA oxidation reaction.…”