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Highlights:(1) Graphene Oxide (GO) caused a significant reduction in fluidity and a slight decrease in compressive strength of AAS mortars.(2) The flexural strength of hardened mortars were improved by adding GO.(3) Layered double hydroxides (LDHs) were observed and confirmed in GO-added AAS system. AbstractDue to its high aspect ratio and outstanding tensile strength, graphene oxide (GO) can dramatically reduce the brittleness of cement-based materials. In this paper, GO nanosheets were successfully synthesised using the modified Hummers' method. Effects of the GO on the fluidity, mechanical properties of alkali-activated slag (AAS) mortars and the microstructure of the AAS pastes were studied.It is found that addition of the GO caused a significant reduction in fluidity and a slight decrease in the compressive strength of the hardened mortars. However, the GO improved the flexural strengths by 20% with a dosage of 0.01 wt. % after 7 days. Large-scale layered double hydroxides (LDHs) were observed using SEM, the compositions of which were identified and EDS and XRD. A possible mechanism of the formation of LDHs in the GO-AAS system is proposed. Due to the Mg 2+ /Al 3+ decomposed from the slag and the Al(OH)4 -formed in the high pH condition in the GO-AAS system, the reaction pathway of LDHs 2 can be regarded as a , This research provides a further understanding of the effect of graphene oxide which has a potential application of GO in AASC.

Li-ion hybrid electrochemical capacitors (Li-HECs) with higher energy density than electric double layer capacitors (EDLC) and larger power density than current rechargeable batteries are attractive candidates in future energy related applications. However, the electrochemical properties of current Li-HECs are greatly restricted by its Li-ion insertion type of electrode materials. Herein, we report an efficient approach to prepare one dimensional T-Nb 2 O 5 nanowires growth on activated carbon cloth as freestanding hybrid electrodes for Li-HECs. The T-Nb 2 O 5 nanowires with diameter of 20∼50 nm and length of several micrometers cross with each other and form a three dimensional (3D) porous network. The designed hybrid electrodes can deliver a gravimetric capacitance as high as 220 mAh g −1 at current density of 0.5 C and advanced cycle life with capacity retention of 86% after 1000 cycles at 5 C. The outstanding electrochemical performances are mainly attributed to the reduction in the lithium ion diffusion length brought by the crossed porous structure. And the enhancement of electron transportation enjoys the benefit from the in-situ growth of T-Nb 2 O 5 nanowires on carbon cloth and the binder-free electrode structure.

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