Active Site Engineering on Two-Dimensional-Layered Transition Metal Dichalcogenides for Electrochemical Energy Applications: A Mini-Review

Abstract

Two-dimensional-layered transition metal dichalcogenides (2D-layered TMDs) are a chemically diverse class of compounds having variable band gaps and remarkable electrochemical properties, which make them potential materials for applications in the field of electrochemical energy. To date, 2D-layered TMDs have been wildly used in water-splitting systems, dye-sensitized solar cells, supercapacitors, and some catalysis systems, etc., and the pertinent devices exhibit good performances. However, several reports have also indicated that the active sites for catalytic reaction are mainly located on the edge sites of 2D-layered TMDs, and their basal plane shows poor activity toward catalysis reaction. Accordingly, many studies have reported various approaches, namely active-site engineering, to address this issue, including plasma treatment, edge site formation, heteroatom-doping, nano-sized TMD pieces, highly curved structures, and surface modification via nano-sized catalyst decoration, etc. In this article, we provide a short review for the active-site engineering on 2D-layered TMDs and their applications in electrochemical energy. Finally, the future perspectives for 2D-layered TMD catalysts will also be briefly discussed.

2D Transition Metal Dichalcogenides‐Based Electrocatalysts for Hydrogen Evolution Reaction

“…Through various approaches such as interfacial bonding, electrical contact, morphological changes, defects, phases, composition, and lattice strain, interface engineering may successfully enhance the electronic structures of active sites, which might appropriately optimize the binding energy, targeting intermediates such as hydrogen. [ 253–258 ] Xu et al. has successfully demonstrated by potential‐temperature depended electrodeposition strategies, we have shown the ultrathin Ni(OH) 2 /Ni 3 S 2 nanosheets (1.8 nm) as a self‐assembled nanoforest based electrocatalyst ( Figure a).…”

Bimetallic Co–Mo sulfide/carbon composites derived from polyoxometalate encapsulated polydopamine-decorated ZIF nanocubes for efficient hydrogen and oxygen evolution

“…Based on the electrocatalytic performance and the material characterization results, the remarkable improvement in electrocatalytic performance of the bimetallic Co–Mo–S/C composite obtained at 600 °C can be ascribed to the synergistic effect of following factors: (1) the evenly distributed ultra-small defect-rich Co–Mo–S phase nanoparticles that maximize the active-surface-area-to-volume-ratio and increase the number of exposed active sites; the abundant lattice distortions, defects in the ultra-small nanoparticles are active sites for the HER and OER; 16,17 (2) heteroatoms including the S element from H 2 S gas, as well as the N element from the PDA coating and the organic linker in ZIF-67, even a trace amount of P derived from PMA, leads to heteroatom N and S-doped composites, which modulates the electronic structure of neighbouring C atoms and provides enhanced active sites for the HER and OER; 25,26 (3) the strong interactions between Co and Mo in the Co–Mo–S phase improve the electron conductivity of the composites and is favourable for charge transfer during the electrocatalytic reaction; 58,59 and (4) the porous carbon support offers high surface area and provides access routes to the reaction active sites, facilitate the easy mass transportation during the electrocatalytic reaction. 22,23…”

“…Besides introducing cobalt into MoS 2 , the electrochemical efficiency of the electrocatalysts can be strategically promoted by active site engineering strategies, including edge-site formation, nano-sized TMD and highly curved structures formed on the MoS 2 crystals. 16 Those ultra-fine open-ended nanostructures with rich defects enable the catalysts to expose a higher density of active sites for the key reactions, consequently leading to improved electrocatalytic activity. 17,18 In order to maintain the fine nanostructure of electrocatalysts, to prevent heat-induced sintering 19 and high surface energy induced agglomeration of the active components, 20 a graphitic carbon matrix can be introduced to isolate the electrocatalytically active MoS 2 nanoparticles.…”

High‐Performance Flexible Piezo–Tribo Hybrid Nanogenerator Based on MoS2@ZnO‐Assisted β‐Phase‐Stabilized Poly(Vinylidene Fluoride) Nanocomposite

“…For the enchanting features and different types of potential applications, the two‐dimensional (2D) layered transition metal dichalcogenides (TMDs) attract a huge attention nowadays. [ 19,20 ] Molybdenum disulfide (MoS 2 ) is one such kind of TMDs that has superior, distinctive functional properties that includes high current‐carrying capacity and large carrier mobility that come out with emerging applications. [ 21 ] MoS 2 has very interesting structure, with different crystal phases such as 1‐layer hexagonal unit cell (1H), 2‐layer hexagonal crystal cell (2H), and three‐layer rhombohedral unit cell (3R).…”