Effectively Regulating\nElectrooxidation of Formic\nAcid over Bimetallic PtCo Alloys via the Integration of Theory and\nExperiment

Challenges\nin directly regulating the reaction pathways\nin the\nelectrooxidation of formic acid have hindered widespread applications\nin direct formic acid fuel cells (DFAFCs). Hence, we report directly\ntuning the reaction pathway of formic acid oxidation (FAO) to avoid\nCO poisoning over the bimetallic PtCo alloys. The PtCo alloys are\nfabricated by using a facile one-step microwave method, avoiding the\nuse of organic solvents and minimizing environmental pollution. The\nPt<sub>1</sub>Co<sub>1</sub> alloy displays a specific surface area\nof 17.58 m<sup>2</sup> g<sup>–1</sup> and exhibits a 121-fold\nincrease in mass activity (1.18 A mg<sub>Pt</sub><sup>–1</sup>) compared to its counterpart Pt (<0.01 A mg<sub>Pt</sub><sup>–1</sup>). It also far outperforms Pt<sub>3</sub>Co<sub>1</sub> (0.09 A mg<sub>Pt</sub><sup>–1</sup>) and Pt<sub>1</sub>Co<sub>3</sub> (0.95 A mg<sub>Pt</sub><sup>–1</sup>) alloys. <i>In situ</i> attenuated total reflection infrared spectra further\nconfirm that the bimetallic PtCo alloys catalyzed FAO through the\ndirect pathway to CO<sub>2</sub> formation, suggesting that adding\nCo plays a crucial role in enhancing Pt’s resistance to CO\npoisoning. Density functional theory calculations further indicate\nthat the incorporation of Co into the Pt coordination environment\nis crucial for altering the formation of transition intermediates,\nwhich can form a more stable bond with the HCOO intermediate, which\nis formed by breaking the O–H bond. Specifically, on the Pt<sub>1</sub>Co<sub>1</sub> alloy with 50% Co incorporation, the free energy\nfor HCOO* formation is significantly lower (−0.296 eV) compared\nto that of COOH* (0.028 eV). This trend is reversed when compared\nwith pure Pt (0.196 eV for HCOO* and −0.190 eV for COOH*),\nthereby promoting FAO via a direct pathway. This work provides a reference\nfor the rational development of high-efficiency Pt-based alloy electrocatalysts.