Quantum Monte Carlo method for metal-film catalysis: Water addition to CO adsorbed on Pt/Al(111), efficient hydrogen production

Abstract

Recently, it has become more urgent to reduce combustion of hydrocarbon fuels. This is motivated by limited resources and the critical levels of carbon dioxide effluent produced in this way. A sustainable alternative is hydrogen, which can be produced catalytically. Here, we consider water-gas shift. Initially, carbon monoxide (CO) is adsorbed on platinum monolayers, supported by cheap Al(111). The CO reacts with water to produce hydrogen. CO2 is also produced. It is removed by mineralization and the hydrogen evolved selectively. This work describes using Quantum Monte Carlo methods that are the only ones accurate enough to investigate the early steps of this catalyzed reaction at close-packed Pt/Al(111). Many chemical reactions involve bond dissociation poorly described by Hartree–Fock and DFT methods. This process is often the key to rate-limiting reaction steps at solid surfaces. This work demonstrates a novel quantum Monte Carlo (QMC) methodology using our embedded active site approach. The water-gas shift reaction step studied is water addition to CO preadsorbed on a Pt monolayer supported by Al(111). The water molecule is only partially dissociated. Its oxygen atom binds to CO giving adsorbed COOH and Pt–H. This concerted addition is rate limiting. In subsequent steps, the adsorbed formate species (with acidic hydrogen) decomposes to carbon dioxide and, after proton migration to Pt–H, molecular hydrogen is obtained as the clean product. The QMC activation barrier is exactly found at the correct lower value than for pure Pt: 64.8 ± 1.5 kJ/mol (Sharma et al. in Ref. 3), due to activation by longer bonds on an Al(111) template. © 2023 Elsevier Inc.