Ultra-small Pt3Co intermetallic compounds: for efficient electrocatalytic methanol oxidation

Abstract

To alleviate the sluggish kinetics exhibited by anodic Pt-based catalysts in the methanol oxidation reaction (MOR), N-doped carbon nanotube (N-CNTs) supports with uniform anchoring sites were synthesized by calcination pyrolysis, which provided abundant anchoring sites for the subsequent deposition of Pt₃Co. For the first time, small-sized and highly dispersed ordered Pt₃Co intermetallic compounds with different sizes were synthesized by adjusting the hydrothermal reaction temperature employed in the low-temperature N-anchoring strategy. The microstructure and physicochemical properties of Pt₃Co/N-CNTs with different Pt₃Co sizes were analyzed by XRD, STEM, and AC-STEM, and their electrochemical performances were evaluated by a three-electrode system. The results demonstrated that the Pt₃Co synthesized at 140 °C exhibited the superior MOR activity and stability. Specifically, its mass and area specific activities were 4905.3 mA mg⁻¹_Pt and 74.2 mA cm⁻¹ surpassing those of commercial Pt/C (1089.5 mA mg⁻¹_Pt and 16.5 mA cm⁻¹). Moreover, after 800 CV cycles, the current density still retained 78.9% of its initial MOR activity, thus demonstrating superior stability compared to commercial Pt/C (52.5%). The enhanced electrochemical performance of Pt₃Co/N-CNTs-140 can be attributed to the smaller particles size (2.15 ± 0.03 nm) of Pt₃Co, which maximizes the exposure of active site, resulting in a larger electrochemically active area and reduced activation energy for MOR. This effect not only enhances the noble metal utilization but also boosts electrocatalytic activity, thereby providing a new idea for designing robust MOR electrocatalysts with exceptional MOR activity and durability.