Lightweight conductive graphene/thermoplastic polyurethane foams exhibited stable piezoresistive sensing signals at a strain of up to 90%.

Thermoplastic polyurethane (TPU) based conductive polymer composites (CPCs) with a reduced percolation threshold and tunable resistance-strain sensing behavior were obtained through the addition of synergistic carbon nanotubes (CNT) and graphene bifillers. The percolation threshold of graphene was about 0.006 vol% when the CNT content was fixed at 0.255 vol% that is below the percolation threshold of CNT/TPU nanocomposites. The synergistic effect between graphene and CNT was identified using the excluded volume theory. Graphene acted as a 'spacer' to separate the entangled CNTs from each other and the CNT bridged the broad gap between individual graphene sheets, which was beneficial for the dispersion of CNT and formation of effective conductive paths, leading to better electrical conductivity at a lower conductive filler content. Compared with the dual-peak response pattern of the CNT/TPU based strain sensors, the CPCs with hybrid conductive fillers displayed single-peak response patterns under small strain, indicating good tunability with the synergistic effect of CNT and graphene. Under larger strain, prestraining was adopted to regulate the conductive network, and better tunable single-peak response patterns were also obtained. The CPCs also showed good reversibility and reproductivity under cyclic extension. This study paves the way for the fabrication of CPC based strain sensors with good tunability.

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3535 www.MaterialsViews.com wileyonlinelibrary.comhave attracted considerable interest because they meet several criteria for efficient PEC water splitting, such as high theoretical solar-to-hydrogen effi ciency (over 15%) and suitable band edge positions for unassisted water splitting.Ta 3 N 5 , [ 8c ] LaTiO 2 N, [ 8a ] and SrNbO 2 N [ 8b ] photoelectrodes prepared by electrophoretic deposition (EPD) methods function as photoanodes for water oxidation. However, considerable water splitting photocurrents have only been achieved with Ta 3 N 5 photoanodes, regardless of the fact that LaTiO 2 N and SrNbO 2 N materials can absorb comparable wavelengths of sunlight and possess similar band edge positions as Ta 3 N 5 . The easier reduction of Ti 4+ and Nb 5+ ions in comparison with Ta 5+ during the high temperature ammonolysis process is considered to produce defects in the bulk and therefore result in less active LaTiO 2 N and SrNbO 2 N powders. [ 9 ] Optimizing the structure and crystallinity of LaTiO 2 N and SrNbO 2 N photoelectrodes may afford desirable improvements in PEC performance, considering that charge carrier transport among the fi lm particles (or layers) depends largely on these parameters. [ 7c ] Increasing photoelectrode crystallinity has been demonstrated to be effective in improving PEC performance by reducing the charge carrier recombination rate. [ 10 ] Effi cient electron and hole transport rely on long-range fi lm continuity and reduced hole transport distance, respectively, which require different fi lm morphological characteristics. [ 11 ] It is desirable but always challenging to obtain highly crystalline interconnected particle fi lm with small particle size. [ 3b ] Despite the above rules to follow and previous work on TaON and Ta 3 N 5 photoanodes to refer to, obtaining highly photo-active LaTiO 2 N photoelectrodes (and more broadly, all the potentially available (oxy)nitride photoelectrodes) is still a great challenge, suggesting that charge transport limitations remain. The goal of this study is to defi ne the limitations present in these (oxy) nitride photoelectrodes, using LaTiO 2 N as an example. Finally, we reveal that the poor electron transport associated with insuffi cient inter-particle connection contributes to the suppressed PEC activities of LaTiO 2 N photoanodes, which cannot be eliminated through necking treatment alone. [ 8c ] Here, the With a theoretical maximum photocurrent of ca. 12.5 mA cm −2 under AM 1.5 G 100 mW cm −2 irradiation, the presently achieved plateau photocurrent of about 0.6 mA cm −2 on bare LaTiO 2 N photoanodes indicates the presence of serious charge transport limitations. Only recently, a plateau photocurrent of about 4 mA cm −2 was achieved on precious IrO 2 modifi ed LaTiO 2 N photoanodes prepared by a rather expensive and complex method, without discussing the intrinsic mechanism of improved photocurrents. In this study, by establishing highly crystalline porous LaTiO 2 N particles and superior interparticle connectivity with reduced density of...