Tetrathiomolybdate Modified Au Electrodes: Convenient Tuning of the kinetics of Electron Transfer and its application in Electrocatalysis

TL;DR

This study demonstrates that ammonium tetrathiomolybdate (ATM) forms stable, tunable multilayer coatings on gold electrodes, enabling control over electron transfer kinetics and enhancing electrocatalytic performance.

Contribution

It introduces a simple method to modify gold electrodes with ATM multilayers, allowing precise tuning of electron transfer rates and catalytic activity for electrocatalysis applications.

Findings

ATM forms stable, air- and pH-tolerant multilayers on Au.

The interfacial charge transfer rate can be tuned by layer thickness.

Catalytic kinetics can be switched from mass transfer to charge transfer limited.

Abstract

Ammonium tetrathiomolybdate (ATM) spontaneously self assembles on Au electrodes forming a hydrophilic, air stable, pH (3-11) tolerant multilayer that is stable over a reasonably large potential window. The ATM functionalized Au electrodes can adsorb iron porphyrin catalysts and act as O2 reducing electrodes. These electrodes are stable enough to perform rotating disk electrochemistry (RDE) as well as rotating ring disk electrochemistry (RRDE) experiments. The X-ray photoelectron spectroscopy (XPS) data indicate that the sulphide atoms of ATM anchors a single ATM layer on to Au and the subsequent layers grow vertically due to the presence of hydrogen bonding NH4+ counter-ions. The formation and growth of these ATM adlayers is investigated using atomic force microscopy (AFM), scanning electron microscopy (SEM) and a series of electrochemical data. The ATM functionalized Au electrodes have double layer capacitance comparable to those reported for Au electrode bearing short chain alkyl thiol self assembled monolayer (SAM). Importantly, the rate of interfacial charge transfer (CT) can be tuned by controlling the thickness of the adlayers by simply adjusting the deposition time. Importantly the kinetics of a catalyst adsorbed on this ATM adlayer can be switched from mass transfer limited to CT limited regime by adjusting the deposition time.