Study of Antimony and Fluorine Doped Tin Oxide in Acidic Medium
Authors: Corona-Elizarraras Luis R , Alpuche-Aviles Mario A. , Cavaliere Sara , Jimenez-Morales Ignacio 
Published: August 2024

In recent decades, the high-energy demand has generated interest in renewable energies and has become a more pressing issue for the development of cost-effective and eco-friendly conversion and storage technologies.1 Solar conversion systems are very attractive to address this problem, either in photovoltaic systems or in systems that store solar energy in chemical form ("solar fuels").2-3 However, there are challenges in terms of functionality, such as (1) finding suitable materials for photon absorption and (2) developing materials for the water electrolysis reaction to produce hydrogen as a solar fuel.4

Materials include catalysts and catalyst supports that allow a stable operation of a cell. Sb-doped tin oxide (ATO) has recently been used as an electrocatalyst support under acidic conditions and proposed as an alternative to F-doped tin oxide (FTO). In this talk, we will address our studies in acidic media of the fundamental electrochemistry of ATO to determine the potential window corresponding to the operation of the material in acid solutions.

Experimental. The experiments were performed in a 3-electrode cell. A glassy carbon electrode of 0.0706 cm2 surface area was used as working electrode (WE), a graphite rod of 0.618 cm diameter as counter electrode (CE), and an Ag/AgCl as reference electrode (RE). The RE was placed in a double junction, and the electrolyte used was a 0.5 M H2SO4 solution (Ultrex® II Ultrapure Reagent). Electrochemical measurements were made on a CH instruments electrochemical workstation potentiostat (CHI 760D). Open circuit potential (OCP) and cyclic voltammograms (CV) were collected. The electrolyte was deoxygenated with Ar, and an Ar blanket was kept on top of the electrochemical cell surface.

Cavaliere and coworkers had synthesized an antimony-doped tin oxide (ATO) with microwaves5 and carried out different studies regarding the applications of ATO as support toward proton-exchange membrane fuel cell (PEMFC)6. Our studies of ATO were mainly focused on the electrochemical activity of anodic potentials. Figure 1 shows two oxidation peaks: one at 0.147 V and the other at -0.253 V both vs NHE. We have assigned the peak at 0.147 V to tin dissolution because of the potentials for SnO2 reduction:7

The material exhibits a potential window of more than one volt in acidic media, which we propose corresponds to the thermodynamic stability of ATO. The anodic and cathodic limits, and the effect of Sb doping on the SnO2 material will be discussed in detail in the presentation.

Acknowledgment

The authors express their gratitude to the National Science Foundation (NSF) for the financial support through NSF project CHE-2108462.

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Figure 1