Abstract
The tuning catalytic functionality of transition metal dichalcogenides (TMDs) with multi-dimensional defects, such as interfaces (2D), edges (1D), and atomic vacancies (0D), is currently considered a promising strategy for energy applications. The pristine edges and plasma-treated basal planes of various TMDs have been extensively studied for practical hydrogen evolution reaction (HER). Here, we demonstrate active HER on the plasma-treated edges of semimetallic layered tungsten ditellurides (WTe2) using a microcell device. Atomic defects, substitutions, and new chemical bonds were locally induced on the basal plane and the edges of WTe2 by mild plasma treatment, leading to catalytically activated WTe2 for HER. The plasma treated WTe2 was characterized by Raman spectroscopy and x-ray photoemission spectroscopy. The local HER at the plasma-treated edges in the microcell device exhibited active electrocatalytic activity with an improved overpotential (325 mV at 10 mA/cm2) and Tafel slope (96 mV/dec), compared with pristine WTe2 (overpotential of 538 mV at 10 mA/cm2 and Tafel slope of 145 mV/dec). Our study proposes a novel strategy to tune the catalytic functionality with multi-dimensional defects for practical catalytic applications.
Highlights
INTRODUCTIONTransition metal dichalcogenides (TMDs) have received attention because of their potential for energy conversion and storage applications, thermoelectric materials, photocatalysts, photovoltaics, batteries, supercapacitors, and electrocatalysts. In particular, extensive studies have revealed that TMDs are efficient electrochemical catalysts for the hydrogen evolution reaction (HER) with nearly zero Gibbs free energies for hydrogen adsorption at various active sites, such as vacancies, interstitial atoms, substitutional atoms, edges, and grain boundaries. Among various TMDs, semimetallic tungsten ditellurides (WTe2) are unique because of their abnormal physical and chemical properties, which originate from its topological characteristics, giant and unsaturated magnetoresistance (MR), high mobility, negative magnetoresistance, quantum spin Hall edges, and edge superconductivity. The prominent atoms on the basal plane of WTe2 behave as active catalytic sites with a moderate Gibbs free energy and could be further optimized with defects or nanostructures. metallic TMDs undergo a structural phase transition due to their defects, substitutions, and strains because of their structural instability, and this could be used for novel materials engineering
We performed energy-dispersive x-ray spectroscopy (EDS) measurement to compare the atomic ratio of the elements in WTe2
There is no significant change in the atomic ratio by the oxygen plasma treatment, indicating that the WTe2 was mildly treated by the oxygen plasma treatment
Summary
Transition metal dichalcogenides (TMDs) have received attention because of their potential for energy conversion and storage applications, thermoelectric materials, photocatalysts, photovoltaics, batteries, supercapacitors, and electrocatalysts. In particular, extensive studies have revealed that TMDs are efficient electrochemical catalysts for the hydrogen evolution reaction (HER) with nearly zero Gibbs free energies for hydrogen adsorption at various active sites, such as vacancies, interstitial atoms, substitutional atoms, edges, and grain boundaries. Among various TMDs, semimetallic tungsten ditellurides (WTe2) are unique because of their abnormal physical and chemical properties, which originate from its topological characteristics, giant and unsaturated magnetoresistance (MR), high mobility, negative magnetoresistance, quantum spin Hall edges, and edge superconductivity. The prominent atoms on the basal plane of WTe2 behave as active catalytic sites with a moderate Gibbs free energy and could be further optimized with defects or nanostructures. metallic TMDs undergo a structural phase transition due to their defects, substitutions, and strains because of their structural instability, and this could be used for novel materials engineering. The prominent atoms on the basal plane of WTe2 behave as active catalytic sites with a moderate Gibbs free energy and could be further optimized with defects or nanostructures.. The theoretical studies showed that charges are exchanged between the transition metal and the incorporated oxygen atoms; the formation of metal–oxygen bonds in TMDs can improve their catalytic activities for HER.. The HER at the basal planes and edges of the flakes before and after oxygen plasma treatment could be locally studied in the exposed windows of the microcell devices. Our study suggests that the tunable catalytic activity by 1D (edges) and 0D (atomic bonds) mixed-dimensional defects fabricated by plasma treatment could be a breakthrough for catalytic applications with 2D TMDs
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