Methyl formate and dimethyl ether electro-oxidation on Pt–Pd–Sn catalyst supported on carbon nanotube decorated with carbon dots

In this work, methyl formate (MF) and dimethyl ether (DME) electro-oxidation was studied on equimolar ratio Pt–Pd–Sn catalyst supported on Vulcan Carbon XC-72, carbon nanotubes (CNT), and CNT–nitrogen-doped carbon dots (NCDs) composite. The ternary catalyst was synthesized by the ethylene glycol-assisted thermal reduction method and NCDs were synthesized by a hydrothermal method in the presence of CNT to form CNT-NCDs composite, in which the NCDs are incorporated onto the CNT surface. The activity of the catalyst in the oxidation of MF and DME was analyzed using cyclic voltammetry and chronoamperometry techniques. The ternary catalyst supported on CNT-NCDs composite (Pt₁Pd₁Sn₁/CNT-NCDs) showed a peak oxidation current of 75 mA/mg and 365 mA/mg for DME and MF, respectively, highest among the studied Pt₁Pd₁Sn₁/XC-72 and Pt₁Pd₁Sn₁/CNT. The onset potential of DME on Pt₁Pd₁Sn₁/CNT-NCDs catalyst shifted negatively by ∼200 mV compared to PtRu. Irrespective of the support material, the ternary catalysts showed a significant negative shift in the onset and peak potential of –CO_ad oxidation compared with commercial PtRu. The oxidation behavior of MF was studied in conjugation with its hydrolysis products methanol, formic acid, and mixed fuel (formic acid + methanol) solution, which disapproves the earlier proposed acid-catalyzed hydrolysis of MF to a significant degree during the electrochemical experiment. Hence, the CNT-NCDs supported ternary catalyst showed high catalytic activity and stability for electro-oxidation of DME and MF.