Phosphorene-quantum-dot-interspersed few-layered MoS2 hybrids as efficient bifunctional electrocatalysts for hydrogen and oxygen evolution

Recent Advances in Engineering of 2D Materials-Based Heterostructures for Electrochemical Energy Conversion

2D materials, such as graphene, transition metal dichalcogenides, black phosphorus, layered double hydroxides, and MXene, have exhibited broad application prospects in electrochemical energy conversion due to their unique structures and electronic properties. Recently, the engineering of heterostructures based on 2D materials, including 2D/0D, 2D/1D, 2D/2D, and 2D/3D, has shown the potential to produce synergistic and heterointerface effects, overcoming the inherent restrictions of 2D materials and thus elevating the electrocatalytic performance to the next level. In this review, recent studies are systematically summarized on heterostructures based on 2D materials for advanced electrochemical energy conversion, including water splitting, CO2 reduction reaction, N2 reduction reaction, etc. Additionally, preparation methods are introduced and novel properties of various types of heterostructures based on 2D materials are discussed. Furthermore, the reaction principles and intrinsic mechanisms behind the excellent performance of these heterostructures are evaluated. Finally, insights are provided into the challenges and perspectives regarding the future engineering of heterostructures based on 2D materials for further advancements in electrochemical energy conversion.

Heterointerface engineering of cobalt molybdenum suboxide for overall water splitting

Highly active and earth-abundant electrocatalysts for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) are of great significance for sustainable hydrogen generation through alkaline water electrolysis. Here, with an aim to enhance the bifunctional electrocatalytic activity of cobalt molybdate towards overall water splitting, we demonstrate a simple method involving the modulation of the cobalt to molybdenum ratio and creation of phase-modulated heterointerfaces. Samples with varying Co/Mo molar ratios are obtained via a microwave-assisted synthesis method using appropriate starting precursors. The synthesis conditions are modified to create a heterointerface involving multiple phases of cobalt molybdenum suboxides (CoO/CoMoO3/Co2Mo3O8) supported on Ni foam (NF). Detailed electrochemical studies reveal that modulating the composition and hence the interface can tweak the bifunctional electrocatalytic activity of the material for HER and OER and thus improve the overall water splitting efficiency with very high durability over 500 h. To further evaluate the practical applicability of the studied catalyst in water splitting, an alkaline electrolyser is fabricated with the optimized cobalt molybdenum suboxide material (CMO-1.25) as a bifunctional electrocatalyst. A current density of 220 mA cm-2 @1.6 V and 670 mA cm-2 @1.8 V was obtained, and the device showed very good long-term durability.

Quasi-one-dimensional phosphorene nanoribbons grown on silicon by space-confined chemical vapor transport

Phosphorene nanoribbons (PNRs) combine the flexibility of one-dimensional (1D) nanomaterials with the large specific surface area and the edge and electron confinement effects of two-dimensional (2D) nanomaterials. In spite of the substantial advances in bulk black phosphorus (BP) manufacturing, achieving PNRs without degradation is still a big challenge. In this work, we present a strategy for the space-confined chemical vapor transport synthesis of quasi-one-dimensional surface-passivated monocrystalline PNRs on a silicon substrate. The growth mechanism of the PNRs is proposed by combining experimental results and DFT calculations, indicating that the P₄ molecules can break, restructure, and epitaxially nucleate on the surface of the Au₃SnP₇ catalyst, and finally prefer to grow along the zigzag (ZZ) direction to form PNRs. The low gas flow rate and an appropriate phosphorus molecule concentration allow the growth of PNRs with structural integrity, which can be regulated by the amount of red phosphorus and the confined space.

Phosphorene quantum dots: synthesis, properties and catalytic applications

Phosphorene quantum dots (PQDs) belong to a new class of zero-dimensional functional nanostructures with unique physicochemical and surface properties in comparison with few-layer phosphorene and other 2D analogues. Tunable band gap as a function of number of layers, ease of passivation and high carrier mobility of PQDs have attracted considerable attention in catalysis research due to which spectacular progress has been made in PQD research over the last few years. PQDs are now considered as promising catalytic materials for electrocatalytic water splitting and nitrogen reduction, lithium-sulfur batteries, solar light-driven energy devices and biocatalysis, either in pristine form or as an active component for constructing heterostructures with other 2D materials. In the light of these recent advances, it is worthwhile to review and consolidate PQD research in catalytic applications to understand the challenges ahead and suggest possible solutions. In this review, we systematically summarize various synthetic strategies including ultrasonic and electrochemical exfoliation, solvothermal treatment, blender breaking, milling, crushing and pulsed laser irradiation. Furthermore, the physiochemical properties of PQDs are discussed based on both experimental and theoretical perspectives. The potential applications of PQDs in catalysis with special emphasis on photocatalysis (solar light-driven energy devices) and electrocatalysis (oxygen evolution reactions and hydrogen evolution reactions) -are critically discussed along with the present status, challenges and future perspectives.