Engineered MoSe2-based heterostructures for efficient electrochemical hydrogen evolution reaction

Leyla Najafi; Sebastiano Bellani; Reinier Oropesa-Nuñez; Alberto Ansaldo; Mirko Prato; Antonio Esau Del Rio Castillo; Francesco Bonaccorso

arXiv · 1903.08951

Engineered MoSe2-based heterostructures for efficient electrochemical hydrogen evolution reaction

Leyla Najafi·Sebastiano Bellani·Reinier Oropesa-Nuñez·Alberto Ansaldo·Mirko Prato·Antonio Esau Del Rio Castillo·Francesco Bonaccorso

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Abstract

Two-dimensional transition metal-dichalcogenides are emerging as efficient and cost-effective electrocatalysts for hydrogen evolution reaction (HER). However, only the edge sites of their trigonal prismatic phase show HER-electrocatalytic properties, while the basal plane, which is absent of defective/unsaturated sites, is inactive. Here, we tackle the key challenge that is increasing the number of electrocatalytic sites by designing and engineering heterostructures composed of single-/few-layer MoSe2 flakes and carbon nanomaterials (graphene or single-wall carbon nanotubes (SWNTs)) produced by solution processing. The electrochemical coupling between the materials that comprise the heterostructure effectively enhances the HER-electrocatalytic activity of the native MoSe2 flakes. The optimization of the mass loading of MoSe2 flakes and their electrode assembly via monolithic heterostructure stacking provided a cathodic current density of 10mAcm-2 at overpotential of 100mV, a Tafel slope of 63mVdec-1 and an exchange current density (j0) of 0.203 Acm-2. In addition, electrode thermal annealing in a hydrogen environment and chemical bathing in n-butyllithium are exploited to texturize the basal planes of the MoSe2 flakes (through Se-vacancies creation) and to achieve in situ semiconducting-to-metallic phase conversion, respectively, thus they activate new HER-electrocatalytic sites. The as-engineered electrodes show a 4.8-fold enhancement of j0 and a decrease in the Tafel slope to 54mVdec-1.

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Leyla Najafi, Sebastiano Bellani, Reinier Oropesa-Nuñez, Alberto Ansaldo, Mirko Prato, Antonio Esau Del Rio Castillo, Francesco Bonaccorso. 2019-03-21. Engineered MoSe2-based heterostructures for efficient electrochemical hydrogen evolution reaction. https://arxiv.org/abs/1903.08951

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