Study on Crystal Plane Adjustment of Pt/P-CNTs Catalyst and Its Electrocatalytic Performance in Methanol Oxidation

To improve the electrocatalytic methanol oxidation (MOR) performance of platinum (Pt)-based catalysts in direct methanol fuel cells (DMFCs), this study uses phosphorus-doped carbon nanotubes (P-CNTs) as a support material. Through a hydrothermal method, different proportions of potassium bromide (KBr) are introduced as a structural directing agent to prepare a series of Pt/P-CNTs-M catalysts (where M represents the molar ratio of KBr to Pt). The study systematically investigates the mechanism by which KBr regulates the crystal plane of Pt nanoparticles and its structure–activity relationship. Physical characterization revealed that KBr selectively regulates Pt crystal plane growth through Br− adsorption. When M = 30, Pt/P-CNTs-30 exhibited the highest proportion of exposed Pt(111) crystal planes (27.21%), with Pt0 content reaching 51.64%, and featured moderate particle size (2.22 nm) and uniform dispersion. Electrochemical testing indicates that the MOR mass-specific activity of this catalyst reaches 3559.85 mA·mg−1Pt, which is 1.17 times that of Pt/P-CNTs-0; it exhibits the lowest charge transfer impedance, with a current density of 488.25 mA·mg−1Pt still maintained after 3600 s of chronoamperometry testing, and a more negative CO oxidation onset potential, demonstrating optimal resistance to poisoning. The study indicates that an appropriate KBr ratio can synergistically optimize Pt crystal plane structure and electronic states, providing a theoretical basis for the design of high-efficiency fuel cell catalysts.