Selective catalysts for the hydrogen oxidation and oxygen reduction reactions by patterning of platinum with calix[4]arene molecules

Abstract

The design of new catalysts for polymer electrolyte membrane fuel cells must be guided by two equally important fundamental principles: optimization of their catalytic behaviour as well as the long-term stability of the metal catalysts and supports in hostile electrochemical environments. The methods used to improve catalytic activity are diverse, ranging from the alloying and de-alloying of platinum to the synthesis of platinum core-shell catalysts. However, methods to improve the stability of the carbon supports and catalyst nanoparticles are limited, especially during shutdown (when hydrogen is purged from the anode by air) and startup (when air is purged from the anode by hydrogen) conditions when the cathode potential can be pushed up to 1.5 V (ref. 11). Under the latter conditions, stability of the cathode materials is strongly affected (carbon oxidation reaction) by the undesired oxygen reduction reaction (ORR) on the anode side. This emphasizes the importance of designing selective anode catalysts that can efficiently suppress the ORR while fully preserving the Pt-like activity for the hydrogen oxidation reaction. Here, we demonstrate that chemically modified platinum with a self-assembled monolayer of calix[4]arene molecules meets this challenging requirement.

Electrocatalysis in Polymer Electrolyte Fuel Cells: From Fundamentals to Applications

“…Although some basic research is carried out on this topic [50], up to now no durable catalyst could be found. iii)…”

Impacts of Surface Functionalization on the Electrocatalytic Activity of Noble Metals and Nanoparticles

“…27 The structure of a calix [4]arene thiol derivative that they used is illustrated in Figure 2a. The wide rim containing sulfur atoms can firmly adsorb onto the Pt(111) terrace, leaving some edge or step sites (i.e., natural defects) and narrow terraces between the calix [4]arene [4]arene molecules totally suppress the oxygen adsorption/desorption (+0.5 ~ +0.9 V), and most of hydrogen adsorption/desorption (+0.05 ~ +0.4 V), as their coverage increases from 0.84 to 0.98 (from curve A to D).…”

“…The observed exceptional selectivity is not unique to the Pt(111)-calix system and has also been observed on Pt(100) and polycrystalline Pt electrodes, as well as Pt nanoparticles. 27,28 The successful preparation of oxygen-tolerant Pt catalysts for HOR indicates that surface functionalization of Pt surfaces is a promising approach to tuning the selectivity of electrocatalysts, which has great applications such as methanol-tolerant ORR catalysts.…”

The Synthesis of Diquinone and Dihydroquinone Derivatives of Calix[4]arene and Electrochemical Characterization on Au(111) surface

“…Cavities are potential sites for sieving cations with small ionic radius such as H + or Li + . [21][22][23] The letter is relevant to the enhanced accessibility of the active species in the energy conversion and storage systems. The crucial step in synthetic routes was the introduction of anchor functional groups.…”