Deactivation and regeneration of a benchmark Pt/C catalyst toward oxygen reduction reaction in the presence of poisonous SO2 and NO

Abstract

SO₂ is considered as the most poisonous ambient contaminant to proton exchange membrane fuel cell (PEMFC) cathodes, leading to severe Pt deactivation and oxygen reduction reaction (ORR) performance loss. Great efforts have been devoted to studying the deactivation and regeneration of SO₂-poisoned Pt/C catalysts, but far less to cases with coexisting NO. Herein, the deactivation and regeneration processes of Pt surfaces during ORR in the presence of both SO₂ and NO (in different molar ratios) are investigated by means of in situ electrochemical infrared spectroscopy and density functional theory (DFT) calculations. Interestingly, NO presents a stronger affinity to Pt sites than SO₂—if an appropriate NO : SO₂ ratio is applied, SO₂ adsorption can be completely inhibited. Besides, the competitive adsorption of NO can weaken the Pt–S bond and expel adsorbed SO₂. Given that adsorbed NO is readily reduced, a faster regeneration is observed if NO and SO₂ are simultaneously fed into the cathode.