Enhancing carbon monoxide tolerance in ethanol electrooxidation using cobalt tetraphenylporphyrin-modified platinum catalysts: An experimental and density functional theory study

The susceptibility of platinum to CO poisoning limits the use of Pt/C in direct alcohol fuel cells. Here, cobalt tetraphenylporphyrin (TPPCo) was assembled onto commercial Pt/C as a molecular cocatalyst for ethanol electrooxidation in 0.5 M H 2 SO 4 and characterized using FTIR, SEM, EDS, XPS, and cyclic voltammetry, complemented by density functional theory (DFT). Over 500 cycles, Pt/C/TPPCo retained its oxidation response better than Pt/C, and the ethanol oxidation and CO reoxidation peaks decreased by 52% and 45% against 71% and 56%, respectively. This durability was achieved despite a lower electroactive area (12.2 vs. 47.5 m 2 /g Pt), indicating an electronic and chemical rather than structural origin. XPS revealed the coexisting Pt 0 /Pt 2+ /Pt 4+ and Co 2+ /Co 3+ states, consistent with an interfacial, bifunctional Pt-TPPCo contact rather than alloying. DFT showed that TPPCo strengthens Pt-cluster anchoring (−8.34 eV, increasing to −10.55 eV under high CO coverage) and buffers the platinum charge state, raising the charge transferred from Pt under CO from 0.36 to 0.71 e − , which is characteristic of the active, CO-free surface. Mechanistically, TPPCo stabilizes the Pt d -states against CO-induced saturation, while its Co(II)/Co(III) couple, operating near 0.65 V/NHE, supplies hydroxyl species that oxidize platinum-bound CO and regenerate the cobalt center, offering a simple route to more CO-tolerant, durable Pt/C electrocatalysts.