Defect-Engineered Charge Transfer in a PtCu/Pr_xCe_1–xO₂ Carbon-Free Catalyst for Promoting the Methanol Oxidation and Oxygen Reduction Reactions

Platinum (Pt) and Pt-based alloys have been extensively studied as efficient catalysts for both the anode and cathode of direct methanol fuel cells (DMFC). Defect engineering has been revealed to be practicable in tuning the charge transfer between Pt and transition metals/supports, which leads to the charge density rearrangement and facilitates the electrocatalytic performance. Herein, Pr-doped CeO 2 nanocubes were used as the noncarbon support of a PtCu catalyst. The concentration and structure of oxygen vacancy ( V o ) defects were engineered by Pr doping. Besides the V o monomer, the oxygen vacancy with a linear structure is also observed, leading to the one-dimensional PtCu. The V o concentration shows the volcanic scenario as Pr increased. Accordingly, the activities of PtCu/Pr x Ce 1– x O 2 toward methanol oxidation and oxygen reduction reactions exhibit the volcanic scenario. PtCu/Pr 0.15 Ce 0.85 O 2 exhibits the optimal catalytic performance with the specific activity 3.57 times higher than that of Pt/C toward MOR and 1.34 times higher toward ORR. The MOR and ORR mass activities of PtCu/Pr 0.15 Ce 0.85 O 2 reached 1.05 and 0.12 A·mg –1, which are 3.09 and 0.92 times the values of Pt/C, respectively. The abundant V o afforded surplus electrons, which tailored the electron transfer between PtCu and Pr x Ce 1– x O 2, leading to enhanced catalytic performance of PtCu/Pr x Ce 1– x O 2 . DFT calculations on PtCu/Pr 0.15 Ce 0.85 O 2 revealed that Pr doping reduced the band gap of CeO 2 and lowered the overpotential.