A Universal In-Situ Interfacial Growth Strategy for Various MXene-Based van der Waals Heterostructures with Uniform Heterointerfaces: The Efficient Conversion from 3D Composite to 2D Heterostructures.

Two-dimensional (2D) van der Waals heterostructures endow individual 2D material with the novel functional structures, intriguing compositions, and fantastic interfaces, which efficiently provide a feasible route to overcome the intrinsic limitations of single 2D components and embrace the distinct features of different materials. However, the construction of 2D heterostructures with uniform heterointerfaces still poses significant challenges. Herein, a universal in-situ interfacial growth strategy is designed to controllably prepare a series of MXene-based tin selenides/sulfides with 2D van der Waals homogeneous heterostructures. Molten salt etching by-products that are usually recognized as undesirable impurities, are reasonably utilized by us to efficiently transform into different 2D nanostructures via in-situ interfacial growth. The obtained MXene-based 2D heterostructures present sandwiched structures and lamellar interlacing networks with uniform heterointerfaces, which demonstrate the efficient conversion from 3D composite to 2D heterostructures. Such 2D heterostructures significantly enhance charge transfer efficiency, chemical reversibility, and overall structural stability in the electrochemical process. Taking 2D-SnSe2/MXene anode as a representative, it delivers outstanding lithium storage performance with large reversible capacities and ultrahigh capacity retention of over 97% after numerous cycles at 0.2, 1.0, and 10.0 A g-1 current density, which suggests its tremendous application potential in lithium-ion batteries.

Fe2 O3 /FePO4 /FeOOH Ternary Stepped Energy Band Heterojunction Photoanode with Cascade-Driven Charge Transfer and Enhanced Photoelectrochemical Performance.

Controlling the charge transfer pathway in semiconductors is an important method to improve charge separation efficiency and enhance photoelectrochemical activity. In this work, a Fe2 O3 /FePO4 /FeOOH nanorod photoanode with stepped energy band structure is prepared by a hydrothermal and water bath method. The charge separation efficiency of the ternary heterojunction is higher than that of the traditional type II heterojunction, which might be due to the efficient cascade charge transfer and separation effect of the ternary stepped energy band heterojunction. The H2 and O2 evolution rates for photoelectrochemical water splitting of Fe2 O3 /FePO4 /FeOOH photoanode are 0.247 and 0.111 µmol min-1 , which is 2.15 and 1.95 times that of the Fe2 O3 /FePO4 photoanode, respectively. The incident photocurrent efficiency (IPCE) of Fe2 O3 /FePO4 /FeOOH photoanode under 365 nm light irradiation is 1.5 and 1.8 times that of Fe2 O3 /FePO4 and Fe2 O3 /FeOOH photoanodes, respectively. This work provides an attractive strategy for solar energy conversion to construct efficient photoelectrochemical photoanode materials.

Fe2O3 nanorods/CuO nanoparticles p-n heterojunction photoanode: Effective charge separation and enhanced photoelectrochemical properties.

Fe2O3/CuO p-n heterojunction photoelectrode films were fabricated by growing CuO nanoparticles on Fe2O3 nanorods via an impregnation method. The content of CuO in Fe2O3/CuO films was changed to study the role of CuO on the p-n heterojunction. The obtained Fe2O3/CuO photoelectrodes exhibited high intensity of visible-light absorption and excellence photoelectrochemical (PEC) performance. The incident photocurrent efficiency (IPCE) of Fe2O3/CuO photoanode reached 11.4% under 365 nm light irradiation, which is 2.6 times higher than that of bare Fe2O3 photoanode. In a PEC water splitting reaction, the H2 and O2 production rates for Fe2O3/CuO-3 were 0.294 and 0.130 µmol/min. The enhanced PEC performance was mainly contributed by the enhanced charge separation and the synergism achieved in Fe2O3/CuO p-n heterojunctions. This work could provide a new route to construct efficient Fe2O3-based composite photoelectrodes for the PEC.