Oxygen vacancy strategy enhancing the performance of TiO2/CNT supported ultrafine Pt catalyst for the oxygen reduction reaction

Abstract

Economic viability and durability are pivotal challenges limiting the commercial application of proton exchange membrane fuel cells (PEMFC). The development of low Pt usage oxygen reduction reaction catalysts with high catalytic activity and durability is imperative. Carbon support corrosion, as well as Pt particles agglomeration and exfoliation are primary causes of commercial Pt/C catalyst degradation. Here, a composite materials formed by TiO₂ containing oxygen vacancy (O_V) and carbon nanotube (CNT) was used as a functional support to successfully load Pt nanoparticles (NPs). The oxygen vacancy facilitated interactions between TiO₂(O_V) and Pt, enhancing the anchoring of Pt NPs and suppressing particle growth. The Pt/TiO₂(O_V)-CNT demonstrates excellent performance with mass activity of 788 mA/mg_Pt @0.85 V, the half-wave potential increased 34 mV and the tafel slope decreased by 11.89 mVdec⁻¹ compared to commercial Pt/C. The durability of Pt/TiO₂(O_V)-CNT nearly 3-fold that of commercial Pt/C with negligible decay of half-wave potential (0.9 %) and mass activity (16 %). Density functional theory calculations and X-ray photoelectron spectroscopy indicated that the charge transfer from TiO₂(O_V) to Pt facilitates the formation of strong metal-support interactions (SMSI), leading to a downward shift in the d-band center of Pt and a reduction in the binding strength to *OOH, thus lowering the activation energy of the rate-determining step which in turn promoting the activity of ORR. This study provides a reliable approach for designing catalysts with high activity and durability.