Latest publications
Metallic Twin Boundaries Boost the Hydrogen Evolution Reaction on the Basal Plane of Molybdenum Selenotellurides
T. Kosmala, H. C. Diaz, Hannu‐Pekka Komsa, Yujing Ma, A. V. Krasheninnikov, M. Batzill, S. Agnoli, 
Advanced Energy Materials, 2018.

The hydrogen evolution reaction (HER) is a fundamental process that impacts several important clean energy technologies. Great efforts have been taken to identify alternative materials that could replace Pt for this reaction or that may present additional functional properties such as optical activity and advanced electronic properties. Herein, a comparative study of the HER activity for ultrathin films of MoTe2, MoSe2, and their solid solutions on highly oriented pyrolytic graphite is reported. Combining advanced characterization techniques and density functional theory calculations with electrochemical measurements, it is shown that the chemical activity of the scarcely reactive 2H phases can be boosted by the presence of metallic twin boundaries. These defects, which are thermodynamically stable and naturally present in Mo‐enriched MoTe2 and MoSe2, endow the basal plane of the 2H phase with a high chemical activity, which is comparable to the metastable 1T polymorph.

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Highly Efficient MoS2/Ag2S/Ag Photoelectrocatalyst Obtained from a Recycled DVD Surface
T. Kosmala, D. Mosconi, G. Giallongo, G. A. Rizzi, and G. Granozzi, 
ACS Sustainable Chem. Eng.,  2018.

An efficient photoelectrocatalyst for hydrogen evolution reaction (HER) was prepared by electrochemical deposition of MoS2 on the Ag nanostructured surface of a commercial writable digital versatile disc (DVD). The deposition was performed by reduction of MoS42– ions and the concomitant production of HS– ions led to the formation of Ag2S nanoparticles. The result was a composite material MoS2/Ag2S/Ag characterized by the formation of uniformly distributed n–p nanojunctions that make the performances of this easy to prepare and cheap electrocatalyst comparable or better than those of similar MoS2 based systems. This study suggests a viable opportunity to turn an abundant waste into an added-value material.

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Enhancing the oxygen electroreduction activity through electron tunnelling: CoOx ultrathin films on Pd(100)
T. Kosmala, L. Calvillo, S. Agnoli, and G. Granozzi, 
ACS Catalysis, 2018, 8, pp 2343–2352.

Electron transfer is the most crucial step in several electrochemical reactions; therefore, finding alternative ways for its control represents a huge step toward the design of advanced electrocatalytic materials. We demonstrate that the electrons from an oxide-buried metal interface can be efficiently exploited in electrochemical reactions. This is proven by studying the electrochemical activity of model systems constituted by cobalt oxide ultrathin (<2 nm) films epitaxially grown on Pd(100). Metal/metal oxide interfacial hybridization and electron tunnelling from the metal substrate through the oxide endow CoOx ultrathin films with exceptional electrochemical activity and improved poison tolerance. In situ XPS and Raman measurements indicate that during the oxygen reduction reaction, CoO is transformed into CoOOH, whereas Co3O4 is stable. These results demonstrate that the in situ study of ultrathin films on single crystals is a powerful method for the identification of materials active phase and of novel phenomena such as electron tunnelling.

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