A series of N-doped graphene (N-graphene)/CdS nanocomposites were synthesized by calcination and characterized by X-ray diffraction, transmission electron microscopy, high-resolution transmission electron microscopy, Raman spectroscopy, N2 adsorption analysis, ultraviolet–visible diffuse reflectance spectroscopy, and X-ray photoelectron spectroscopy. The photocatalytic activity of as-prepared N-graphene/CdS for hydrogen production from water under visible light irradiation at λ ≥ 420 nm was investigated. The results show that N-graphene/CdS nanocomposites have a higher photocatalytic activity than pure CdS. Transient photocurrents measured with a photoelectrochemical test device show that the photocurrent of the N-graphene/CdS sample is much increased as compared to the sole CdS. This enhanced photoresponse indicates that the photoinduced electrons in the CdS prefer separately transferring to the N-doped graphene. As a consequence, the radiative recombination of the electron–hole pairs is hampered and the photocatalytic activity is significantly enhanced for the N-graphene/CdS photocatalysts. The amount of N-graphene is an important factor affecting photocatalytic activity of N-graphene/CdS nanocomposites; the optimum amount of N-graphene is ca. 2 wt %, at which the N-graphene/CdS sample displays the highest reactivity. Photocatalytic activity of graphene/CdS and GO/CdS composites for H2 production from water under visible light irradiation was also measured. The relative order of reactivity for the synthesized catalysts was found to be N-graphene/CdS > graphene/CdS > GO/CdS > CdS. Furthermore, the N-graphene/CdS photocatalyst does not show deactivation for H2 evolution for longer than 30 h, indicating that the cocatalyst of N-graphene as a protective layer can prevent CdS from photocorrosion under light irradiation. Our findings demonstrate that N-graphene as a cocatalyst is a more promising candidate for development of high-performance photocatalysts in the photocatalytic H2 production.

is still hindered by some main fundamental obstacles, including the insulating nature of sulfur and lithium sulfides (Li 2 S), and the notorious shuttle effect of lithium polysulfides (LiPSs) intermediates during cycling process. The shuttle effect brings about not only the loss of the active materials but also the anode corrosion, leading to rapid capacity degradation and low Coulombic efficiency. [4,5] Carbon nanomaterials with high electrical conductivity, desirable porous structure, and controlled dimensions have been devoted to the design of sulfur hosts [6][7][8][9][10][11][12][13] or interlayers [14][15][16] to physically restrain LiPSs in the cathode area, however, the weak interactions between nonpolar carbon and polar LiPSs discount the effectiveness during the long-term cycling. Chemical trapping of LiPSs with polar transition metal compounds such as TiO 2 , MnO 2 , etc., via polar-polar interactions is an available approach to mitigate the LiPSs shuttling. [17][18][19][20][21] Nonetheless, when the sulfur content and electrode mass loading are high, the massive generated LiPSs are difficult to be immobilized due to the adsorption saturation by these compounds. The detrimental shuttle effect in lithium-sulfur batteries mainly results from the mobility of soluble polysulfide intermediates and their sluggish conversion kinetics. Herein, presented is a multifunctional catalyst with the merits of strong polysulfides adsorption ability, superior polysulfides conversion activity, high specific surface area, and electron conductivity by in situ crafting of the TiO 2 -MXene (Ti 3 C 2 T x ) heterostructures. The uniformly distributed TiO 2 on MXene sheets act as capturing centers to immobilize polysulfides, the hetero-interface ensures rapid diffusion of anchored polysulfides from TiO 2 to MXene, and the oxygen-terminated MXene surfaceis endowed with high catalytic activity toward polysulfide conversion. The improved lithium-sulfur batteries deliver 800 mAh g −1 at 2 C and an ultralow capacity decay of 0.028% per cycle over 1000 cycles at 2 C. Even with a high sulfur loading of 5.1 mg cm −2 , the capacity retention of 93% after 200 cycles is still maintained. This work sheds new insights into the design of highperformance catalysts with manipulated chemical components and tailored surface chemistry to regulate polysulfides in Li-S batteries.

Potassium-ion batteries (KIBs) are receiving increasing interest in grid-scale energy storage owing to the earth abundant and low cost of potassium resources. However, their development still stays at the infancy stage due to the lack of suitable electrode materials with reversible depotassiation/potassiation behavior, resulting in poor rate performance, low capacity, and cycling stability. Herein, the first example of synthesizing single-crystalline metallic graphene-like VSe nanosheets for greatly boosting the performance of KIBs in term of capacity, rate capability, and cycling stability is reported. Benefiting from the unique 2D nanostructure, high electron/K -ion conductivity, and outstanding pseudocapacitance effects, ultrathin VSe nanosheets show a very high reversible capacity of 366 mAh g at 100 mA g , a high rate capability of 169 mAh g at 2000 mA g , and a very low decay of 0.025% per cycle over 500 cycles, which are the best in all the reported anode materials in KIBs. The first-principles calculations reveal that VSe nanosheets have large adsorption energy and low diffusion barriers for the intercalation of K -ion. Ex situ X-ray diffraction analysis indicates that VSe nanosheets undertake a reversible phase evolution by initially proceeding with the K -ion insertion within VSe layers, followed by the conversion reaction mechanism.