Análise do envenenamento de superfícies de Pt e SnO2/Pt por monóxido de carbono na presença de combustível: uma abordagem teórica

Abstract

The growing demand for renewable energy has driven the development of various alternatives for clean energy production, such as electrolyzers and fuel cells. These devices employ metallic catalysts to promote oxidation reactions at the anode and reduction at the cathode, enabling the direct production of energy (in fuel cells) or hydrogen (in electrolyzers), which can be used as fuel in other applications. However, the loss of catalytic activity and stability, mainly caused by surface poisoning due to the accumulation of carbon monoxide (CO), compromises the efficiency of these devices. Adsorbed CO hinders the interaction of reactant species with the catalyst surface, reducing its performance. In this work, density functional theory (DFT) was employed to investigate the adsorption of CO on platinum surfaces with different crystallographic orientations – Pt(111), Pt(100), and Pt(110) – aiming to identify which structure is more susceptible to poisoning. The effect of coating these surfaces with SnO2 was also analyzed to evaluate the oxide’s ability to reduce CO adsorption and, consequently, mitigate poisoning. To assess the impact of poisoning, molecules such as glycerol and ethanol, commonly used as anodic fuels, were adsorbed on the surfaces at different levels of CO coverage. The results show that CO adsorption is energetically favorable on all Pt surfaces, with greater affinity for the less packed structure, Pt(110). The presence of CO significantly reduces the adsorption of fuel species. On the other hand, on surfaces coated with SnO2, CO adsorption is reduced, while the adsorption of other species is enhanced due to the third-body effect. Thus, both the crystallographic orientation and the tin oxide coating directly influence the catalytic activity and resistance to CO poisoning.