Single atom catalysts provide exceptional activity and turnover frequencies. However, single atom catalytic activity is often measured by dispersing atoms and nanoparticles on catalyst support. This makes is difficult to study the fundamental activity from a single atom in real electrochemical environments. Here, we report catalytic activity from precise number of sulfur vacancies on two dimensional molybdenum disulfide grown by chemical vapor deposition. The vacancies were introduced by carefully varying the dose of helium ions in a helium ion microscope (HIM). We then counted the number of vacancies per cm2 using high resolution scanning transmission electron microscope (STEM). The catalytic activity was measured using micro-electrochemical cells previously developed in our group. The devices allow control of the area over which the catalytic properties are measured to ensure that activity is only coming from the sulfur vacancies. Our results show that the catalytic properties of the MoS2 improves with the number of vacancies. More importantly, we demonstrate that it is possible to extract the activity from a single sulfur vacancy. We have found that at a vacancy concentration of 5.4 x 1014 cm-2, the intrinsic turn over frequency (TOF) and Tafel slope of a single atomic vacancy is ~ 6 s-1 and 38 mV/dec, respectively. The TOF is amongst highest reported and the Tafel slope approaches that of platinum.

Single atomic cacancy catalysis

2019 Spring National Meeting

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