Search

Si, as a narrow bandgap semiconductor with a broadband absorption for sunlight, is considered to be a very competitive photoelectrode material for solar‐driven photoelectrochemical (PEC) water splitting. However, there are major barriers in construction of efficient and stable Si‐based PEC cell, including low photovoltage, sluggish reaction kinetics, and poor stability in electrolytes. This review focuses on the strategies to solve these issues and summarizes recent progress. The working principles of PEC water splitting are first introduced. Then the strategies for improving Si‐based photoelectrode performances are discussed, including (1) the regulation of Si surface morphology for enhancing light harvesting, (2) band structure engineering strategies to reduce recombination of photogenerated carriers, and (3) modification of protection layers for long stability and loading cocatalysts on Si‐based photoelectrodes for accelerating water splitting. Lastly, we have presented some issues of Si‐based photoelectrode materials, which should be addressed in future research. [ABSTRACT FROM AUTHOR]

Generally, photocatalytic reaction efficiency decreases quickly with increasing irradiation intensity. Thus, it is a great challenge to achieve a high reaction efficiency under strong irradiation. Volume photocatalysis (VPs) is a new strategy for improving photocatalytic reaction efficiency. Herein, hierarchically porous polymeric carbon nitride (PCN) U‐PCN‐480 as a novel volume photocatalyst is fabricated by a template‐free pyrolysis of needle‐like urea. It is found for the first time that the hierarchical pore structure endows U‐PCN‐480 with the enhanced photoabsorption ability under strong irradiation. Consequently, Pt/U‐PCN‐480 displays excellent VPs activity for hydrogen evolution in the formic acid reaction system. Notably, the activity and apparent quantum efficiency (AQE) are significantly enhanced with increasing irradiation intensity, and the AQE reaches 62.7% and 70.4% at 400 and 380 nm with the irradiation intensity of 30.5 mW cm−2, respectively, the highest values among the reported data for PCN‐based photocatalysts. This effect of enhanced activity and AQE is the result of the synergy between VPs and the enhanced photoabsorption. The findings offer an approach to resolve the difficult problem of low photocatalytic reaction efficiency under strong irradiation and open a way to develop efficient photocatalyst materials and reaction systems. [ABSTRACT FROM AUTHOR]

Realizing ultrathin water and generating an abundant water/air interface in the interconnected pores of photothermal materials is an effective way to boost the solar‐driven water evaporation rate, but still a great challenge. Herein, confinement capillarity (CC) of photothermal thin coating on porous sponge for significantly enhancing the solar‐driven water evaporation is proposed. The thin coating is composed of abundant agminated black/hydrophilic nanoparticles (BHNPs), and the channels among the BHNPs can generate strong capillarity for water transportation. Water can be spontaneously limited and transported among the agminated nanoparticles, rather than fill in the interconnected pores of the sponge. Thus, ultrathin water layer can be realized on the outer/inner surface of the sponge skeleton, without precisely controlling water supply. The thin water layer can not only expose as much evaporation area as possible by increasing the vapor escape channel, but also prevent solar energy to heat excess water. Thanks to the CC, the rate of solar steam generation can be greatly improved. Moreover, the photothermal material with CC can maintain its high evaporation rate during the whole day, and can remove the salt during night time, highlighting its recyclability and anti‐salt‐accumulation property. Moreover, the CC can be readily scaled up for practical applications. [ABSTRACT FROM AUTHOR]

Oxygen vacancy plays a key role in the photocatalytic processes of oxide semiconductors. However, it usually needs high hydrogenation temperature to form oxygen vacancy for SrTiO3. To decrease the temperature, Pt was preloaded on SrTiO3 to transform H2 into the active hydrogen through hydrogen spillover. As a result, the surface oxygen vacancy of Pt/SrTiO3‐x forms at low temperature to 150 °C. Without Pt loading, the defects of SrTiO3 cannot occur even at 400 °C. As the hydrogenation temperature increases, the surface oxygen vacancy of Pt/SrTiO3‐x rises, and a thin disorder overlayer on the facet loaded with metal Pt appears at 400 °C; whereas at 600 °C, besides the disorder overlayer, the surface defects at the facets without Pt and bulk defects are produced, indicating the controllable formation of oxygen vacancies. With the increasing of hydrogenation temperature, the activity of Pt/SrTiO3‐x enhances, and reaches the maximum at 400 °C. The produced H2 amount of Pt/SrTiO3‐x prepared at 400 °C is about 3 times as high as that of Pt/SrTiO3. The activity of Pt/SrTiO3‐x obtained at 600 °C is significantly lower than that at 400 °C. The surface oxygen vacancies are responsible for the enhanced activity; while the decreased specific surface and bulk defects produced at high hydrogenation temperature reduce the activity. New method: The method is developed to produce oxygen vacancy for SrTiO3 at low temperature by hydrogen spillover due to photodeposited Pt. The formation of the oxygen vacancies is controllable. The surface oxygen vacancies formed at low temperature promote significantly photocatalytic hydrogen evolution; while the decreased specific surface and bulk defects produced at high hydrogenation temperature reduce the activity. [ABSTRACT FROM AUTHOR]

Cd0.5Zn0.5S solid solutions were prepared by hydrothermal method and co-precipitation method. The synthesized materials were characterized by means of X-ray diffraction (XRD), transmission electron microscopy (TEM), Brunauer-Emmett-Teller (BET) surface area measurement and ultraviolet-visible diffuse reflectance spectra (UV-Vis DRS). The photocatalytic activity was tested in the reaction of hydrogen evolution from aqueous solutions of glycerol under visible light irradiation (λ ≥ 420 nm). Zn0.5Cd0.5S-G prepared by co-precipitation method with glycerol as solvent exhibits higher photocatalytic activity. This can be due to Zn0.5Cd0.5S-G possessing higher surface area, which is beneficial to the adsorption of electron donor on catalyst surface. Glycerol improves notably photocatalytic hydrogen evolution with its simultaneous degradation. The possible mechanism of photocatalytic reaction for hydrogen evolution with simultaneous glycerol degradation was discussed preliminary. © 2015 American Institute of Chemical Engineers Environ Prog, 35: 141-148, 2016 [ABSTRACT FROM AUTHOR]