Two-state reaction guaranteed high efficiency hydrogen production in Sn+H2O reaction: A preliminarily theoretical study based on single molecule model

Abstract The Sn + H2O reaction is important in both hydrogen production through solar thermochemical redox cycles and investigations like the treatment of nuclear reactors or flame inhibition. Based on single molecule model, this work systematically explores its possible reacting channels in different spin multiplicities at CCSD(T)//DFT level of theory to reveal the underlined mechanism for its reported efficient hydrogen production. It is found that the singlet and triplet potential energy surfaces cross each other during the water attacking process, which makes the hydrogen production channel in the singlet state energetically favored. Quantitative calculations about the possibility of surface crossing and spin inversion with respect to minimum energy crossing point, spin-orbit coupling coefficient and intersystem crossing probability confirm that the optimal reacting pathway involves the two-state reaction scenario. This special reactive pattern makes hydrogen production not only possible but also efficient. Analysis of the equilibrium constant of reactive channels and their variation with temperature reveals the performance of two-state reaction channel agrees well with reported data range and nontrivial temperature dependence.