Structure – Catalytic Behavior Relationships in TiO₂-Carbon Composite Supported Pt Electrocatalysts: A Case Study

Abstract

Composite types of supports made of TiO₂ and carbonaceous materials provide higher stability for the Pt electrocatalysts under the working conditions of polymer electrolyte membrane fuel cells than the traditional carbon supports. We have demonstrated in our previous work that composites with general formula of 75 wt.% Ti_(1-x)Mo_xO₂-25 wt.% C (x = 0–0.2; C = traditional Black Pearls (BP) carbon) were promising supports which provided increased stability for the Pt electrocatalysts. In this study, the effect of nitrogen doping of the carbonaceous component of the composite was explored. 75 wt.% TiO₂-25 wt.% carbon composite supports were prepared using graphite oxide (GO), N-doped GO and N-doped multilayer graphene. Electrocatalysts were made by loading the supports with 20 wt.% Pt. The systems were compared based on their physicochemical properties determined by low-temperature nitrogen adsorption, X-ray powder diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and conductivity measurements. The activity of the catalysts was investigated by conventional methods in a 3-electrode electrochemical cell. The results of various characterization methods contributed to the understanding of the difference in the electrochemical properties of N-free and N-containing catalyst samples. While GO was favorable for this composite supported catalyst, its N-doping strongly influenced the growth of TiO₂, forming an almost continuous coating of small TiO₂ crystals. This quasi-insulating TiO₂ layer between the Pt catalytic sites and the conductive part of the composite resulted in poor electrochemical activity. Mixing the sample with carbon improved its conductivity, which resulted in a significant increase in the oxygen reduction activity.

Keywords:

• Composite support
• electrocatalyst, cyclic voltammetry (CV)
• graphite oxide
• N-doped graphite oxide
• N-doped multilayer graphene

Acknowledgement

The authors thank Tamás Szabó for providing graphite oxide, Anett Lázár for XRD, and Zoltán May for ICP-OES measurements.

Authors contributions

Conceptualization, Emília Tálas; Methodology, Emília Tálas and Irina Borbáth; Catalyst preparation, Ilgar Ayyubov and Camelia Berghian-Grosan, Investigation of electrocatalytic reactions, XRD measurements, Ilgar Ayyubov; Investigation by TEM, Erzsébet Dodony; Investigation by XPS, Zoltán Pászti; Investigation by low-temperature nitrogen physisorption, Ágnes Szegedi; Writing-Original Draft Preparation, Emília Tálas, Zoltán Pászti and Irina Borbáth; Supervision, Adriana Vulcu and András Tompos; Funding Acquisition: András Tompos. All authors have read and agreed to the published version of the manuscript.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This research was funded by Project no. RRF-2.3.1-21-2022-00009, titled National Laboratory for Renewable Energy has been implemented with the support provided by the Recovery and Resilience Facility of the European Union within the framework of Programme Széchenyi Plan Plus. Financial support in the frame of VEKOP-2.3.3–15- 2016–00002 is greatly appreciated (Erzsébet Dodony).