Defect Engineering of van der Waals Solids for Electrocatalytic Hydrogen Evolution

Abstract

Van der Waals solids with tunable band gaps and interfacial properties have been regarded as a class of promising active materials for electrocatalytic hydrogen evolution reaction (HER). However, due to the anisotropic features, their basal planes are usually electrochemically inert, only a few unsaturated edge atoms could serve as active centers to actuate H 2 generation. Hence, material utilization and productivity efficiency are insufficient for practical applications. Recently, diverse defects have been confirmed to enable tailoring atomic configurations and electronic properties of van der Waals solids, thus triggering their superior catalytic activity of in-plane atoms while introducing high amount of new active sites. In this minireview, we summarize the state-of-the-art progress of defect engineering in van der Waals solids for HER, focusing in particular on their advantages in material modification and corresponding catalytic mechanisms. We also propose the challenges and perspectives of these catalytic materials in terms of both experimental synthesis and fundamental understanding of the defect structures.

Molecular Engineering Strategies toward Molybdenum Diselenide Design for Energy Storage and Conversion

“…Vacancy engineering, which is also known as defect engineering, is used to create surface vacancies (including anion and cation vacancies) to tailor the physical and chemical properties of the host and fabricate various functional materials (especially for TMDs). [133][134][135] In particular, vacancy engineering is used to improve the properties of group VIB TMDs via several mechanisms: 1) vacancies can expose more active sites on the surface of pristine materials and the uncoordinated Ce-doped MoSe 2 @CNTs Ce HER Decreases the adsorption free energy; exposes more active sites [128] arrangement of active sites promotes reactant adsorption and activation, 2) vacancy can regulate surface reaction pathways and lower reaction energy barriers to accelerate catalytic processes, 3) vacancies can trigger phase transition and stabilize the metastable 1T phase, which improves the electrochemical properties of the materials. Two primary routes are used to create Se vacancies on the surface of MoSe 2 : annealing reduction and surface etching (Figure 11).…”

Van der Waals Heterostructures—Recent Progress in Electrode Materials for Clean Energy Applications

“…The unique physical and electrochemical properties of vdW heterostructures make them an intriguing option for potential HER catalysts. In reality, their anisotropic nature makes a pure sample a poor catalytic choice [43][44][45][46]. Atoms are firmly bonded in a satisfied coordination environment leading to an inert structure.…”

Emerging Two-Dimensional Carbonaceous Materials for Electrocatalytic Energy Conversions: Rational Design of Active Structures through High-Temperature Chemistry

“…During the past few decades, two-dimensional (2D) covalent nanomaterials have emerged as efficient electrocatalysts for many essential electrochemical reactions due to their unique structural features and electronic properties ( e.g ., high surface area, large density of edge sites, and high stability of covalent bonds), providing great opportunities for fine-tuning the active moieties toward those selective electrocatalysis . Since the delineation for all-carbon graphene as a model case in 2004, the drastic differences in the anisotropic and electronic properties of atomically thin nanomaterials and their bulk counterparts have sparked enthusiasm to explore other types of 2D materials, including but not limited to single- or few-layered transition metal dichalcogenides (TMDs), metal oxides, layered double hydroxides (LDHs), metal carbides/nitrides ( e.g ., MXenes), metallenes, graphitic carbon nitride (g-C 3 N 4 ), hexagonal boron nitride ( h -BN), and a family of monoelemental compounds (such as black phosphorus, arsenene, antimonene and bismuthine). − These 2D materials all exhibit thicknesses of one or several atoms or in the low nanometer region and typically possess strong covalent bonds within the 2D-plane, whereas weak van der Waals interactions are active between layers. , Notably, owing to the unique structural features and the redistributed electron density derived from their anisotropy, nearly all explored 2D nanomaterials exhibit different properties absent in their bulk counterparts, thereby endowing them with desirable functionalities toward a wide spectrum of applications . In this regard, extensive research interest has been garnered to evaluate the efficacy of these 2D nanomaterials in electrocatalysis, as witnessed widely in the hydrogen evolution/oxidation reaction (HER/HOR), oxygen evolution/reduction reaction (OER/ORR), and carbon dioxide reduction reaction (CO 2 RR). − This not only resulted in the discovery of indeed special catalytic properties on those layered 2D composites but also accelerated the development of various material synthesis strategies that are urgently needed to afford desirable 2D electrocatalysts. , …”

“…5−7 These 2D materials all exhibit thicknesses of one or several atoms or in the low nanometer region and typically possess strong covalent bonds within the 2D-plane, whereas weak van der Waals interactions are active between layers. 8,9 Notably, owing to the unique structural features and the redistributed electron density derived from their anisotropy, nearly all explored 2D nanomaterials exhibit different properties absent in their bulk counterparts, thereby endowing them with desirable functionalities toward a wide spectrum of applications. 8 In this regard, extensive research interest has been garnered to evaluate the efficacy of these 2D nanomaterials in electrocatalysis, as witnessed widely in the hydrogen evolution/oxidation reaction (HER/HOR), oxygen evolution/reduction reaction (OER/ ORR), and carbon dioxide reduction reaction (CO 2 RR).…”