Photoelectrocatalytic performance of a system is fundamentally determined by the full absorption of sunlight and high utilization of photoexcited carriers, but efficiency of the latter is largely limited by inefficient charge transfer from the absorber to reactive sites. Here, we propose to construct directional charge transfer channels in a monolithically integrated electrode, taking carbon dots/carbon nitride (CCN) nanotubes and FeOOH/FeCo layered double hydroxide (FFC) nanosheets as a representative, to boost the photoassisted overall water splitting performance. Detailed experimental investigations and DFT calculations demonstrate that the interfacial C–O–Fe bonds between CCN and FFC act as charge transfer channels, facilitating the directional migration of the photogenerated carriers between CCN and FFC surfaces. Moreover, the in situ oxidized Fe/Co species by photogenerated holes trigger lattice oxygen activation, realizing the construction of the Fe–Co dual-site as the catalytic center and efficiently lowering the barrier energy for water oxidation. As a result, the CCN@FFC electrode shows multiple functionalities in photoelectrocatalysis: only a low overpotential of 68 mV, 182 mV, and 1.435 V is required to deliver 10 mA cm–2 current densities for the photoassisted HER, OER, and overall water splitting, respectively. This directional charge transfer modulation strategy may facilitate the design of highly active and cost-effective multifunctional catalysts for energy conversion and storage.

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The behavior of smart concrete beams with embedded shape memory alloy (SMA) bundles is investigated in this study. Two beams measuring 1996 × 99 × 85 cm3, which will be integrated into a smart bridge in a freeway, are manufactured and examined. Each beam contains six trusses of SMA bundles used as actuators to achieve recovery force. The SMA bundles are connected with pre-stressing steel strands and separated from the concrete matrix, so that temperature interaction between SMA bundles and the matrix can be reduced to as low as possible. Some temperature sensors, reinforcement meters, and displacement sensors are used to monitor the active control effect of SMA bundles, all the data are acquired through a 16-channel dynamic data-acquisition system, and each beam is examined several times with different activating current intensity. Experimental results indicate that the recovery force induced by SMA bundles is significant and controllable, the deflection generated by the SMA bundles at the middle span of the beam is about 0.44 mm, and the capability of resisting overload of each beam is about 2.98 kN (average). A relationship between SMA temperature and activating/inactivating time is also formulated. The conclusion is that SMA can be used in civil engineering structures either from a technological or economic aspect.

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