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Photoelectrocatalytic seawater splitting is a promising low-cost method to produce green hydrogen in a large scale. The effects of Cl− ions in seawater on the performance of a photoanode have been reported in previous studies. However, few researches have been done on the roles of Cl− ions in a photocathode. Herein, for the first time, we find that Cl− ions in the electrolyte improve the photocurrent of a Si/In2S3 photocathode by 50% at −0.6 VRHE. An in-situ X-ray photoelectron spectroscopy (XPS) characterization combined with the time-of-flight secondary-ion mass spectrometry by simulating photoelectrochemical conditions was used to investigate the interface charge transfer mechanism. The results suggest that there is an In2+3S3−x(OH)2x layer on the surface of In2S3 in the phosphate buffer solution (PBS) electrolyte, which plays a role as an interface charge transfer mediator in the Si/In2S3 photocathode. The In2+3S3−x(OH)2x surface layer becomes In2+3S3−x(Cl)2x in the PBS electrolyte with NaCl and accelerates the charge transfer rate at the In2S3/electrolyte interface. These results offer a new concept of regulating interface charge transfer mediator to enhance the performance of photoelectrocatalytic seawater splitting for hydrogen production. [ABSTRACT FROM AUTHOR]

Interface charge transfer plays a key role in a photoelectrochemical cell. Recently, a faradaic junction transfer model was proposed that describes the interface charge transfer process. Electrochemical potential is introduced as a thermodynamic descriptor for the structure and composition of the surface faradaic layer of a semiconductor. However, the kinetic process in the faradaic junction model remains unclear. Herein, we introduce a descriptor, the density of storable charge (DOSC), to describe the number of charges that can be stored in a surface faradaic layer at different applied potentials. Moreover, the DOSC of the faradaic layer on the surface of Fe2O3 was modified by Ti doping, and the results suggest that a larger DOSC leads to higher transient photocurrent in a solar rechargeable device, which is helpful for designing other high-performance devices for solar conversion and storage. [ABSTRACT FROM AUTHOR]

Chrysolaminarin, a kind of water-soluble bioactive β-glucan produced by certain microalgae, is a potential candidate for food/pharmaceutical applications. This study identified a marine microalga Isochrysis zhangjiangensis, in which chrysolaminarin production was investigated via nutrient (nitrogen, phosphorus, or sulfur) deprivations (-N, -P, or -S conditions) along with an increase in light intensity. A characterization of the antioxidant activities of the chrysolaminarin produced under each condition was also conducted. The results showed that nutrient deprivation caused a significant increase in chrysolaminarin accumulation, though this was accompanied by diminished biomass production and photosynthetic activity. -S was the best strategy to induce chrysolaminarin accumulation. An increase in light intensity from 80 (LL) to 150 (HL) µE·m−2·s−1 further enhanced chrysolaminarin production. Compared with -N, -S caused more suitable stress and reduced carbon allocation toward neutral lipid production, which enabled a higher chrysolaminarin accumulation capacity. The highest chrysolaminarin content and concentration reached 41.7% of dry weight (%DW) and 632.2 mg/L, respectively, under HL-S, with a corresponding productivity of 155.1 mg/L/day achieved, which exceeds most of the photoautotrophic microalgae previously reported. The chrysolaminarin produced under HL-N (Iz-N) had a relatively competitive hydroxyl radical scavenging activity at low concentrations, while the chrysolaminarin produced under HL-S (Iz-S) exhibited an overall better activity, comparable to the commercial yeast β-glucan, demonstrating I. zhangjiangensis as a promising bioactive chrysolaminarin producer from CO2. [ABSTRACT FROM AUTHOR]

Two-electrode solar rechargeable device is one of the promising technologies to address the problem of solar energy storage in large scale. However, the mechanism of dark output voltage remains unclear and the low volumetric energy density also limits its practical applications. Herein, we report that a Si/CoOx/KBi(aq)/MnOx Faradaic junction device exhibits a photovoltage memory effect, that is, the dark output voltage can precisely record the value of the photovoltage in the device. To investigate the mechanism of the effect, we develop an open circuit potential method to real-time monitor the photo charge and dark discharge processes in the Faradaic junction device. This effect leads to minimized interface energy loss in the Faradaic junction device, which achieves much higher performances than the devices without the effect. Moreover, we realize a portable device with a record value of the dark volumetric energy density (∼1.89 mJ cm−3) among all reported two-electrode solar rechargeable devices. These results offer guidance to improve the performance of a solar rechargeable device and design other photoelectric devices for new applications. A Faradaic junction solar rechargeable device is one of the promising technologies to address the problem of solar energy storage but the working mechanism remains unclear. Here, the authors report a photovoltage memory effect in a portable Si/CoOx/KBi(aq)/MnOx Faradaic junction device. [ABSTRACT FROM AUTHOR]

A two-electrode solar rechargeable device is a potential low-cost method for solar energy conversion and storage. However, a low working voltage limits its practical application. It is significant to develop a solar rechargeable device with a high voltage. Herein, we report a device of BiVO4/CoPi/KPi(aq)/C with a working voltage of about 0.9 V, which is the highest value among all previously reported two-electrode devices. The high voltage comes from the positive onset potential of CoPi, which is used as the energy storage material for the first time. Moreover, we also investigate the reasons for the positive onset potential of CoPi by comparing with other conventional Co-based materials. The results suggest that CoPi has fewer tetrahedral Co(II), which leads to higher oxidation potential than the materials with more octahedral Co(II). This study highlights the importance of choosing energy storage materials with suitable potential windows in a solar rechargeable device and offers guidance to improve the performance. [ABSTRACT FROM AUTHOR]

Engineering the size, shape and crystallinity of organic semiconductor nanostructures (OSNs) offers the opportunity of fine tuning their optoelectronic properties for photocatalytic applications. Here, we report a facile and general 'ice-melting' kinetic control strategy to synthesize OSNs with excellent photocatalytic performance. The ultraslow release and interaction of organic molecules from ice melting yields an ultralow local concentration (∼five orders of magnitude fewer molecules), fundamentally enhancing the energy barrier thus leading to their relaxed and ordered assembly into refined nanocrystals (∼one order of magnitude smaller in size, morphological change from amorphous to crystalline); such nanocrystals display improved light-harvesting and charge transfer properties and consequent photocatalytic efficiency towards degrading organic pollutants compared to standard OSNs, or even commercial titania photocatalysts (Degussa P25); we also generalize the 'ice-melting' kinetic control strategy to synthesize a series of highly photoactive organic nanocrystals. [ABSTRACT FROM AUTHOR]