Dissociation of Sulfuric Acid in Aqueous Solution: Determination of the Photoelectron Spectral Fingerprints of H₂SO₄, HSO₄^–, and SO₄^2– in Water

Abstract

In the work described here, the electronic structure of sulfuric acid in water is explored by liquid-jet photoelectron spectroscopy. From the S2p photoelectron spectra of H 2 SO 4 (aq), measured over a large concentration range and aided by previously reported HSO 4 − /SO 4 2and HSO 4 − /H 2 SO 4 concentration ratios in the bulk solution, we obtain detailed electronic structure information of each species. Comparing our results with previous studies on the dissociation of nitric acid, we argue that the solvation structure of H 2 SO 4 (aq) changes around 5−7 M concentration, at which point a dramatic change in both the HSO 4 − photoelectron peak width and binding energy occurs.

Protonation Dynamics and Hydrogen Bonding in Aqueous Sulfuric Acid

“…The data are collected in Figure 2 and are presented together with our simulation results mimicking the plot of Margarella and co-workers. 35 The number of hydrogen bonds per O water was evaluated from the AIMD trajectories and is depicted in Figure 3. The Figure 4.…”

“…In addition to a large number of theoretical studies of small acid−water clusters, microwave, infrared (IR), optical, vacuum ultraviolet (VUV), and soft X-ray spectroscopy has been applied to study the structure and protonation state of the acid molecules in gas and in liquid phase. 28− 35 Simulations on liquid sulfuric acid 36−41 address the protonation process and the molecular-ion structures present in the solution. Stepwise dissociation was evaluated critically by Fraenkel,42,43 who proposed formation of H 4 SO 5 for concentrations up to 6.9 M.…”

“…However, Fraenkel studied the concentration range from 0 to 6.9 M and therefore the only systems in our simulations that could possibly correspond this range are the 1.5 M (1A, 64W) and 7.1 M (6A, 54W) ones. ratios have been experimentally determined in numerous works 35,54,55. The core−electron binding energies of H 2 SO 4 (aq) have been found to exhibit changes for different concentrations,35 reflecting the protonation state distribution in the system.…”

Evaporation of sulfate aerosols at low relative humidity

“…However, when the mole fraction of S(VI) exceeds ∼ 0.5, H 2 SO 4 can be detected in the solution (Walrafen et al, 2000;Margarella et al, 2013). When H 2 SO 4 is present in the solution, dehydration of H 2 SO 4 to form SO 3 (Reaction R3) can also be important (Wang et al, 2006;Que et al, 2011).…”

Ion Spatial Distributions at the Air– and Vacuum–Aqueous K2CO3 Interfaces

“…In this regard, three prominent analytical techniques have recently proved noteworthy complements to the well established macroscopic techniques of surface tension [8][9] and surface potential [10][11] for the study of air (vacuum)-water interfaces: second harmonic generation (SHG), [12][13][14][15][16][17][18][19][20][21][22] sum-frequency generation (SFG) spectroscopy [23][24][25][26][27][28][29][30][31] and liquid based X-ray photoelectron spectroscopy (XPS). [32][33][34][35][36][37][38][39][40][41][42][43][44][45] All three of these methods are capable of interrogating the microscopic structure of the air (vacuum)-water interface, and often provide complementary information due to the different properties probed. For instance, SFG is a second order non-linear vibrational spectroscopy typically used to investigate the fundamental OH stretching region (between 3100−3500 cm −1 ), which provides detailed information on the structure and orientation of water within the non-centrosymmetric region at the interface.…”