Abstract
Platinum is a noble metal that is widely used for the electrocatalytic production of hydrogen, but the surface reactivity of platinum toward water is not yet fully understood, even though the effect of water adsorption on the surface free energy of Pt is important in the interpretation of the morphology and catalytic properties of this metal. In this study, we have carried out density functional theory calculations with long-range dispersion corrections [DFT-D3-(BJ)] to investigate the interaction of H2O with the Pt (001), (011), and (111) surfaces. During the adsorption of a single H2O molecule on various Pt surfaces, it was found that the lowest adsorption energy (Eads) was obtained for the dissociative adsorption of H2O on the (001) surface, followed by the (011) and (111) surfaces. When the surface coverage was increased up to a monolayer, we noted an increase in Eads/H2O with increasing coverage for the (001) surface, while for the (011) and (111) surfaces, Eads/H2O decreased. Considering experimental conditions, we observed that the highest coverage was obtained on the (011) surface, followed by the (111) and (001) surfaces. However, with an increase in temperature, the surface coverage decreased on all the surfaces. Total desorption occurred at temperatures higher than 400 K for the (011) and (111) surfaces, but above 850 K for the (001) surface. From the morphology analysis of the Pt nanoparticle, we noted that, when the temperature increased, only the electrocatalytically active (111) surface remained.
Highlights
Global research is focusing on clean, renewable, and sustainable energy production
We examine the electronic properties of the system, including simulated scanning tunneling microscopy (STM) images, the work function, and local densities of states
To distinguish between the two competing processes, dissociation and association, and the most likely adsorption mode to occur, the thermodynamic effect of water coverage on the different Pt surfaces was the chemical potential at different temperatures, while in Figure 10b,c, we present the effect of the coverage on the surface free energies in terms of the chemical potential for the dissociatively and molecularly adsorbed H2O molecules on the Pt (001) surface
Summary
Global research is focusing on clean, renewable, and sustainable energy production. H2 gas can be produced via a number of technologies, including from carbon-based fuels[15] or from renewable sources such as biomass[16] and water.[17,18] Among the different routes to the production of H2, the non-carbon-based hybrid sulfur (HyS) cycle has shown itself as a promising, potentially largescale process.[19,20] In this process, the net reaction is the splitting of water into H2 and O2 via the electro-oxidation of SO2/H2SO4 In this system, various anode catalysts have been tested,[20] and metallic platinum (Pt) consistently showed both high activity and stability,[13,21,22] especially when it was supported on carbon particles. Pt is already used as a catalyst[23] in a wide variety of reactions, where water acts as a reactant or spectator, influencing the behavior of the surface.[24]
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