Effectively Regulating Electrooxidation of Formic Acid over Bimetallic PtCo Alloys via the Integration of Theory and Experiment

Challenges in directly regulating the reaction pathways in the electrooxidation of formic acid have hindered widespread applications in direct formic acid fuel cells (DFAFCs). Hence, we report directly tuning the reaction pathway of formic acid oxidation (FAO) to avoid CO poisoning over the bimetallic PtCo alloys. The PtCo alloys are fabricated by using a facile one-step microwave method, avoiding the use of organic solvents and minimizing environmental pollution. The Pt₁Co₁ alloy displays a specific surface area of 17.58 m² g^–1 and exhibits a 121-fold increase in mass activity (1.18 A mg_Pt^–1) compared to its counterpart Pt (<0.01 A mg_Pt^–1). It also far outperforms Pt₃Co₁ (0.09 A mg_Pt^–1) and Pt₁Co₃ (0.95 A mg_Pt^–1) alloys. In situ attenuated total reflection infrared spectra further confirm that the bimetallic PtCo alloys catalyzed FAO through the direct pathway to CO₂ formation, suggesting that adding Co plays a crucial role in enhancing Pt’s resistance to CO poisoning. Density functional theory calculations further indicate that the incorporation of Co into the Pt coordination environment is crucial for altering the formation of transition intermediates, which can form a more stable bond with the HCOO intermediate, which is formed by breaking the O–H bond. Specifically, on the Pt₁Co₁ alloy with 50% Co incorporation, the free energy for HCOO* formation is significantly lower (−0.296 eV) compared to that of COOH* (0.028 eV). This trend is reversed when compared with pure Pt (0.196 eV for HCOO* and −0.190 eV for COOH*), thereby promoting FAO via a direct pathway. This work provides a reference for the rational development of high-efficiency Pt-based alloy electrocatalysts.