Revealing the mechanism of bifunctional PtLa electrocatalyst for highly efficient methanol oxidation, hydrogen...

The development of clean energy solutions, such as fuel cells and hydrogen energy, is crucial for addressing the global energy shortage. Platinum (Pt)-based catalysts are widely used in fuel cells and hydrogen energy generation (for example, via water electrolysis). However, reducing the amount of Pt used while maintaining the catalytic performance of such catalysts is essential. Herein, PtLa catalysts (Pt_xLa_y/C) doped with rare earth element lanthanum (La) with different Pt/La atomic ratios were synthesized using a simple chemical reduction method, resulting in Pt₆₅La₃₅/C, Pt₇₈La₂₂/C, Pt₉₇La₃/C, and Pt₁₀₀/C. These Pt_xLa_y/C catalysts exhibited excellent electrocatalytic activity and stability in methanol oxidation reaction (MOR), hydrogen evolution reaction (HER), and their coupling reaction as MOR||HER under alkaline conditions. The mechanism by which La doping enhances the electrocatalytic properties and stability of Pt-based catalysts was investigated using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), aberration-corrected scanning transmission electron microscopy (AC-STEM), in-situ Fourier transform infrared (FTIR) and operando Raman spectroscopy. For HER, La doping facilitated the adsorption and activation of H₂O at Pt sites, improving water dissociation and *OH desorption and reducing Pt poisoning by *OH. This enhances both the catalytic performance and stability of Pt_xLa_y/C for HER. Pt₇₈La₂₂/C exhibited a considerably lower overpotential of only 111 mV at 100 mA cm^-2 compared to commercial 20 wt% Pt/C (Pt/C-Johnson Matthey (JM)), which requires 153 mV. For MOR, La promotes CO bond cleavage and reduces CO adsorption at the Pt sites, thereby enhancing both the performance and stability of the catalysts. The mass activity (MA) of Pt₇₈La₂₂/C for MOR is 4.44 A mg^-1_Pt, which is 12.33 times higher than that of Pt/C-JM (0.36 A/mg_Pt), and surpasses those of Pt₆₅La₃₅/C, Pt₉₇La₃/C, and Pt₁₀₀/C (2.93, 0.24, and 2.91 A mg^-1_Pt, respectively). Additionally, Pt₇₈La₂₂/C exhibited outstanding catalytic performance for MOR||HER, with a current density of 20 mA cm^-2 at 1.030 V, demonstrating good stability with negligible voltage changes after a 15 h chronoamperometry (CA) testing. This study provides a new strategy for synthesizing Pt-based catalysts with enhanced efficiency and low-energy input for HER||MOR.