Proton Transport Scenarios in Sulfuric Acid Explored via Ab Initio Molecular Dynamics Simulations

Sulfuric acid (H₂SO₄), a highly reactive reagent containing intrinsic protonic charge carriers, has been studied via ab initio molecular dynamics simulations. Specifically, we explore the solvation shell structure of the protonic defects, H₁SO₄^- and H₃SO₄⁺, as well as the underlying proton transport mechanisms in both the neat and hydrated H₂SO₄ solutions. Our findings reveal a significant contraction of the dynamic hydrogen-bonded network around the protonic defects, which resembles features seen in water. The simulations provide estimates of the structural relaxation time scales for proton release from both the covalent O-H bonds (∼23 ps) and the hydrogen bonds (∼0.4 ps). In contrast to water, our analysis of the proton transfer scenarios in sulfuric acid reveals correlated events mediated by the formation of longer (up to four) hydrogen-bonded Grotthuss chains.