Electrochromic smart windows are regarded as a good choice for green buildings. However, conventional devices need external biases to operate, which causes additional energy consumption. Here we report a self-powered electrochromic window, which can be used as a self-rechargeable battery. We use aluminium to reduce Prussian blue (PB, blue in colour) to Prussian white (PW, colourless) in potassium chloride electrolyte, realizing a device capable of self-bleaching. Interestingly, the device can be self-recovered (gaining blue appearance again) by simply disconnecting the aluminium and PB electrodes, which is due to the spontaneous oxidation of PW to PB by the dissolved oxygen in aqueous solution. The self-operated bleaching and colouration suggest another important function of the device: a self-rechargeable transparent battery. Thus the PB/aluminium device we report here is bifunctional, that is, it is a self-powered electrochromic window as well as a self-rechargeable transparent battery.

Tungsten trioxide hydrate (3WO 3 3 H 2 O) films with different morphologies were directly grown on fluorine doped tin oxide (FTO) substrate via a facile crystal-seed-assisted hydrothermal method. Scanning electron microscopy (SEM) analysis showed that 3WO 3 3 H 2 O thin films composed of platelike, wedgelike, and sheetlike nanostructures could be selectively synthesized by adding Na 2 SO 4 , (NH 4 ) 2 SO 4 , and CH 3 COONH 4 as capping agents, respectively. X-ray diffraction (XRD) studies indicated that these films were of orthorhombic structure. The as-prepared thin films after dehydration showed obvious photocatalytic activities. The best film grown using CH 3 COONH 4 as a capping agent generated anodic photocurrents of 1.16 mA/cm 2 for oxidization of methanol and 0.5 mA/cm 2 for water splitting with the highest photoconversion efficiency of about 0.3% under simulated solar illumination.

We report the synthesis of nanostructured tungsten trioxide (WO 3) films and their electrochromic characteristics. Plate-like monoclinic WO 3 nanostructures were grown directly on fluorine-doped tin oxide glass substrates by a simple and low-cost crystal-seed-assisted hydrothermal method. The growth mechanism of the film is investigated. HRTEM analysis reveals the single crystalline quality of the WO 3 nanostructure. The film exhibits tunable transmittance modulation under different voltages and repetitive cycling between the clear and blue states has no deleterious effect on its electrochromic performance after 3000 cycles. The electrochromic device composed of the WO 3 film has high electrochromic stability, colour contrast and reasonable switching response with a colouration efficiency of 38.2 cm 2 C −1 at 632.8 nm.

Zinc oxide (ZnO) nanorods coated with silver (Ag) film on a polyethylene terephthalate (PET)flexible substrate were used as the photo anode for water splitting. The hybrid nanostructures were prepared via low-temperature hydrothermal growth and electron beam evaporation. The effects of plasmonic enhanced absorption, surface recombination inhibition and improved charge transport are investigated by varying the Ag thickness. Light trapping and absorption enhancement are further studied by optimizing the curvature of the PET substrates. The maximum short circuit current density (JSC, 0.616 mA cm -2) and the photoelectron conversion efficiency (PCE, 0.81%) are achieved with an optimized Ag film thickness of 10 nm and substrate bending radius of 6.0 mm. The maximum JSC and PCE are seven times and ten times, respectively, higher than those of the bare ZnO nanorods on flexible substrates without bending. The overall PEC performance improvement is attributed to the plasmonic effects induced by Ag film and improved charge transport due to inhibition of ZnO surface charge recombination. Enhanced light trapping (harvesting) induced by bending the PET substrates further improved the overall efficiency.

The anode microstructural evolution is correlated to its electrochemical characteristics during a long time discharge for conventional nickel-yttria-stabilized zirconia composite anode. Self made anode performance degraded with operation time in humidified hydrogen, with the increases of both ohmic and polarization losses. The anode samples after different discharging times were analysized by 3dimensional microstructure reconstruction based on focused ion beam-scanning electron microscopy technique. Nickel connectivity, nickel-yttria-stabilized zirconia interface area and the active three-phases-boundary length were correlated to the anode degradation. The influences of bulk gas humidity and current density were also investigated to reveal their contributions to the anode degradation.