The charge transfer mechanism of flower spherical-like MnCdS/In 2 S 3 /NiAl-LDHs was analyzed by density functional theory. The presence of a dual S-scheme heterostructure enhanced the photocatalytic hydrogen production and photodegradation activity.
Abstract Recently, hydrovoltaic technology emerged as a novel renewable energy harvesting method, which dramatically extends the capability to harvest water energy. However, the urgent issue restricting its device performance is poor carrier transport properties of the solid surface if large charged interface is considered simultaneously. Herein, a hydrovoltaic device based on silicon nanowire arrays (SiNWs), which provide large charged surface/volume ratio and excellent carrier transport properties, yields sustained electricity by a carrier concentration gradient induced by evaporation‐induced water flow inside nanochannels. The device can yield direct current with a short‐circuit current density of over 55 μA cm −2 , which is three orders larger than a previously reported analogous device (approximately 40 nA cm −2 ). Moreover, it exhibits a constant output power density of over 6 μW cm −2 and an open‐circuit voltage of up to 400 mV. Our finding may pave a way for developing energy‐harvesting devices from ubiquitous evaporation‐driven internal water flow in nature with semiconductor material of silicon.
One of the effective strategies to improve photocatalytic activity of composite materials is to construct a heterostructure using layered double hydroxide (LDH) as the main photocatalytic material in order to accelerate photogenerated charge transfer. In this paper, a novel flower-like spherical ZnCdS/Bi2WO6/ZnAl-LDH with dual type-II heterostructure photocatalytic composite was prepared by a hydrothermal method. ZnAl-LDH in the composite has the characteristic structure of a good hydrotalcite-like compound, and ZnCdS and Bi2WO6 are loaded on the surface of ZnAl-LDH, forming a flower-like spherical with uniform size. Compared with the monomer ZnAl-LDH, ZnCdS/Bi2WO6/ZnAl-LDH composites have significantly wider light absorption range and more uniform aperture distribution. Electrochemical impedance, transient photocurrent, and photoluminescence results of ZnCdS/Bi2WO6/ZnAl-LDH composites show that 20% ZnCdS/Bi2WO6/ZnAl-LDH composites have the highest photocurrent density, the lowest electron transfer resistance, and the lowest electron–hole recombination efficiency. Multi-mode photocatalytic degradation experiments reveal all ZnCdS/Bi2WO6/ZnAl-LDH composites exhibit good ability of photocatalytic degradation. Meanwhile, ZnCdS/Bi2WO6/ZnAl-LDH has enhanced hydrogen production by photolysis with hydrogen production of 633.58 μmol/g within 8 h, which is over 8 times for monomer ZnAl-LDH, and its photocatalytic activity remains stable after three cycles of experiments. Through the capture experiments, the active species during the photocatalytic reaction is identified and the presence of a dual type-II heterostructure in the ZnCdS/Bi2WO6/ZnAl-LDH composite is postulated. The rapid separation and migration of photogenerated charges in the composites is thus achieved due to the close association between ZnCdS, Bi2WO6 and ZnAl-LDH.
Abstract Recently, hydrovoltaic technology emerged as a novel renewable energy harvesting method, which dramatically extends the capability to harvest water energy. However, the urgent issue restricting its device performance is poor carrier transport properties of the solid surface if large charged interface is considered simultaneously. Herein, a hydrovoltaic device based on silicon nanowire arrays (SiNWs), which provide large charged surface/volume ratio and excellent carrier transport properties, yields sustained electricity by a carrier concentration gradient induced by evaporation‐induced water flow inside nanochannels. The device can yield direct current with a short‐circuit current density of over 55 μA cm −2 , which is three orders larger than a previously reported analogous device (approximately 40 nA cm −2 ). Moreover, it exhibits a constant output power density of over 6 μW cm −2 and an open‐circuit voltage of up to 400 mV. Our finding may pave a way for developing energy‐harvesting devices from ubiquitous evaporation‐driven internal water flow in nature with semiconductor material of silicon.
ABSTRACT A comb shaped surface dielectric barrier discharge (SDBD) reactor coupled with polyvinylidene fluoride (PVDF)/Fe 3 O 4 composite nanofibers was investigated to degrade methylene blue (MB) in water. The PVDF/Fe 3 O 4 nanofibers with a rough surface were prepared when the proportion of Fe 3 O 4 NPs in a 14 wt% PVDF spinning solution was 7 wt%. Compared to SDBD plasma alone, the addition of PVDF/Fe 3 O 4 nanofibers significantly increased the degradation rate, degradation amount, kinetic constant, energy efficiency, and chemical oxygen demand removal rate of the MB solution. Active species trapping test revealed that •OH played the most important role during MB degradation, •O 2− , H 2 O 2 , electrons, and holes were also crucial. After five repeated uses, the PVDF/Fe 3 O 4 nanofibers maintained high catalytic activity, chemical stability, and mechanical strength.
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