Reactivity of Sulfur Vacancy-Rich MoS<sub>2</sub> to Water Dissociation
Bo‐An Chen, Andrew J. E. Rowberg, Tuan Anh Pham, Tadashi Ogitsu, Prashant V. Kamat, Sylwia Ptasińska
Abstract
Exposed Mo atoms on the surface of MoS 2 can catalyze certain useful chemical reactions, including the dissociation of water to produce hydrogen. However, a comprehensive understanding of water reactivity on defective MoS 2 surfaces remains elusive. Here, we use in situ near ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) to investigate water dissociation reactions on MoS 2 surfaces before and after Ar + ion beam bombardment. To make the surfaces reactive, we treated them with Ar + ion beam sputtering first, which created exposed Mo sites. Using ultraviolet photoelectron spectroscopy (UPS) and density of states calculations conducted using density functional theory (DFT), we verified that stripping the surface of sulfur atoms creates metallic surface states that can catalyze water dissociation. At elevated H 2 O pressures, XPS measurements combined with DFT calculations suggested the presence of four distinct surface species from dissociated water. Specifically, we found that oxides and hydroxides are prominent at the surface, while chemisorbed and physisorbed H 2 O molecules are also present. This study provides new insights that reveal the prospects of surface-engineered MoS 2 as a catalyst for water dissociation.