A green route is developed to prepare hierarchical porous carbon sheets (HPCS) from biomass directly under air atmosphere without inert gas protection. The as-prepared HPCS with ultra-thin structure, rich O doping sites and large SSA demonstrate excellent specific capacitance and stability when used in supercapacitor.

Hierarchical ZnO composed of ultrathin nanosheets as secondary structures were fabricated through a hydrothermal method. Afterwards, hexagonal wurtzite CdS with diameter between 50-100 nm were incorporated on the wurtzite ZnO sheets with the assistance of ultrasonic irradiation. The hybrid ZnO/ CdS samples were intensively investigated by SEM, TEM, HRTEM, XRD, XPS, PL and the UV-Vis absorption spectrum. The photocatalytic trials confirmed that the ZnO/CdS hierarchical heterostructures exhibit improved degradation efficiency compared to pure ZnO sample under natural sunlight. CdS nanoparticles are believed to serve as photo-sensitizers to extend the absorption spectrum to the visible region and the loading amount was also found to play a crucial role in influencing the degradation efficiency. Moreover, the photodegradation kinetics of RhB via using CdS/ZnO as photocatalysts were also systematically discussed. Finally, a mechanism based on this band-gap alignment was proposed to elucidate the efficiency enhancement of the hybrid photocatalysts.

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The energy and spatial distribution of intragap trap states of the TiO2 photoanode of dye-sensitized solar cells and their impact on charge recombination were investigated by means of time-resolved charge extraction (TRCE) and transient photovoltage (TPV). The photoanodes were built from TiO2 nanospheroids with different aspect ratios, and the TRCE results allowed differentiation of two different types of trap states, that is, deep and shallow ones at the surface and in the bulk of the TiO2 particles, respectively. These trap states exhibit distinctly different characteristic energy with only a slight variation in the particle size, as derived from the results of the density of states. Analyses of the size-dependent TPV kinetics revealed that in a moderate photovoltage regime of about 375-625 mV, the dynamics of electron recombination are dominated by shallow trap states in the bulk, which can be well accounted for by the mechanism of multiple-trap-limited charge transport.

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Activated N-doped porous carbons (a-NCs) were synthesized by pyrolysis and alkali activation of graphene incorporated melamine formaldehyde resin (MF). The moderate N doping levels, mesopores rich porous texture, and incorporation of graphene enable the applications of a-NCs in surface and conductivity dependent electrode materials for supercapacitor and dye-sensitized solar cell (DSSC). Under optimal activation temperature of 700 °C, the afforded sample, labeled as a-NC700, possesses a specific surface area of 1302 m2 g(-1), a N fraction of 4.5%, and a modest graphitization. When used as a supercapacitor electrode, a-NC700 offers a high specific capacitance of 296 F g(-1) at a current density of 1 A g(-1), an acceptable rate capability, and a high cycling stability in 1 M H2SO4 electrolyte. As a result, a-NC700 supercapacitor delivers energy densities of 5.0-3.5 Wh kg(-1) under power densities of 83-1609 W kg(-1). Moreover, a-NC700 also demonstrates high electrocatalytic activity for I3- reduction. When employed as a counter electrode (CE) of DSSC, a power conversion efficiency (PCE) of 6.9% is achieved, which is comparable to that of the Pt CE based counterpart (7.1%). The excellent capacitive and photovoltaic performances highlight the potential of a-NCs in sustainable energy devices.

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