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An efficient strategy is proposed by engineering Co-doped MoS2 coupled with Mo2CTx MXene to enhance the HER performance in alkaline media.

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SYNOPSIS: A facile approach was developed to produce TiO 2 NAs/MoS 2 3D photoanode with different phases (1T or 2H) of MoS 2 for photoelectrochemical water splitting.ABSTRACT: A novel three-dimensional (3D) photoanode with exfoliated MoS 2 nanosheets on the TiO 2 nanorod arrays (TiO 2 NAs) was successfully fabricated by combining hydrothermal and drop-casting methods. The influences of the different phases (1T and 2H) of the MoS 2 nanosheets on the photoelectrochemical (PEC) performances of such a TiO 2 NAs/MoS 2 3D system have been systematically investigated. Parallel experiments revealed that the TiO 2 NAs/1T-MoS 2 composite with optimized 1T-MoS 2 loading exhibited the highest photo-electric conversion efficiency, which was about 440% and 93% higher than those of the TiO 2 NAs and the TiO 2 NAs/2H-MoS 2 counterpart, respectively. The enhanced catalytic performances of the TiO 2 NAs/1T-MoS 2 composite can be attributed to the superior conductivity of 1T-MoS 2 and the strong interaction between TiO 2 NAs and 1T-MoS 2 . The photo-generated holes can therefore transfer from the TiO 2 NAs to the 1T-MoS 2 , thus leading to enhanced charge separation efficiency.(2) May, M. M.; Lewerenz, H.-J.; Lackner, D.; Dimroth, F.; Hannappel, T., Efficient direct solar-to-hydrogen conversion by in situ interface transformation of a tandem structure. Nat. Commun. 2015, 6, 8286, DOI 10.1038/ncomms9286. (3) Hisatomi, T.; Kubota, J.; Domen, K., Recent advances in semiconductors for photocatalytic and photoelectrochemical water splitting. Chem. Soc. Rev. 2014, 43, 7520-7535, DOI 10.1039/c3cs60378d. (4) Han, H. S.; Han, G. S.; Kim, J. S.; Kim, D. H.; Hong, J. S.; Caliskan, S.; Jung, H. S.; Cho, I. S.; Lee, J. K., Indium-tin-oxide nanowire array based CdSe/CdS/TiO 2 one-dimensional oxygen vacancy concentration, and photocatalytic activity. J. Am. Chem. Soc. 2012, 134, 6751-6761, DOI 10.1021/ja300823a. (18) Qin, D.-D.; Bi, Y.-P.; Feng, X.-J.; Wang, W.; Barber, G. D.; Wang, T.; Song, Y.-M.; Lu, X.-Q.; Mallouk, T. E., Hydrothermal growth and photoelectrochemistry of highly oriented, crystalline anatase TiO 2 nanorods on transparent conducting electrodes. Chem. Mater. 2015, 27, 4180-4183, DOI 10.1021/acs.chemmater.5b00782. (19) Zegeye, T. A.; Kuo, C.-F. J.; Wotango, A. S.; Pan, C.-J.; Chen, H.-M.; Haregewoin, A. M.; Cheng, J.-H.; Su, W.-N.; Hwang, B.-J., Hybrid nanostructured microporous carbonmesoporous carbon doped titanium dioxide/sulfur composite positive electrode materials for rechargeable lithium-sulfur batteries. (20) Agegnehu, A. K.; Pan, C.-J.; Tsai, M.-C.; Rick, J.; Su, W.-N.; Lee, J.-F.; Hwang, B. J., Visible light responsive noble metal-free nanocomposite of V-doped TiO 2 nanorod with highly reduced graphene oxide for enhanced solar H 2 production. Int. J. Hydrogen Energ. 2016, 41, 6752-6762, DOI 10.1016/j.ijhydene.2016.03.025. (21) Asahi, R.; Morikawa, T.; Ohwaki, T.; Aoki, K.; Taga, Y., Visible-light photocatalysis in nitrogen-doped titanium oxides. Sun, W.-T.; Yu, Y.; Pan, H.-Y.; Gao, X.-F.; Chen, Q.; Peng, L.-M., CdS quant...

Auxetic mechanical metamaterials (AMMs), as an exciting paradigm of metamaterials, have attracted increasing attention due to their interesting mechanical properties (e.g. negative Poisson's ratio), as well as the emergence of advanced manufacturing technology (e.g. 3D printing). Although various reviews on AMMs, their structures, properties, and applications, have existed, it still lacks a comprehensive review in terms of manufacturing methods. Herein, the latest progress in AMMs is extensively reviewed, including AMMs' structures, characteristics, manufacturing methods, and applications. In addition, the current challenges and future works of AMMs are concluded and discussed. This Review aims to serve as a collection of knowledge that supplies more comprehensive understanding and inspiration to support further developments of AMMs from the perspective of design and manufacturing.

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Acoustic metamaterials (AMs), which are materials composed of subwavelength periodic artificial structures with specific designs, have drawn significant research attention. This is because of the extraordinary abilities of AMs to manipulate acoustic waves compared with those of traditional acoustic materials. In this review, current advances in AM research are comprehensively investigated and summarized. First, major theories regarding AMs, including the acoustic wave equation, crystal lattice and energy band theory, effective medium theory, and general Snell's law, are explained in detail. Existing AM structures are then described and divided into several categories based on their structural characteristics and responses to acoustic waves. Furthermore, to bridge the gap between design and practical application, both conventional and advanced AM manufacturing methods are summarized. The applications of AMs in the fields of acoustic cloaking, acoustic lensing, acoustic absorption, noise reduction, and supernormal sound transmission are particularly delineated. Finally, contemporary challenges, trends, and strategies relevant to AMs are discussed. This review aims to provide a comprehensive collection of AM‐related knowledge, including information regarding physical theories, structures, fabrication approaches, and applications, which will help promote the further development of AMs.