Dual mechanisms based on synergistic effects of evaporation potential and streaming potential for natural water evaporation.

Electricity generation by natural water evaporation generators (NWEGs) using porous materials shows great potential for energy harvesting, but mechanistic investigations of NWEGs have mostly been limited to streaming potential studies. In this study, we propose the coexistence of an evaporation potential and streaming potential in a NWEG using ZSM-5 as the generation material. The iron probe method, salt concentration regulation, solution regulation, and side evaporation area regulation were used to analyze the NWEG mechanism. Our findings revealed that a streaming potential formed as water flowed inside the ZSM-5 nanochannels, driven by electrodynamic effects that increased from the bottom to the top of the generator. In addition, an evaporation potential existed at the surface interface between ZSM-5 and water, which decreased from the bottom to the top as the evaporation height of the generator increased. The resulting open-circuit voltage (Voc) depended on the balance between the evaporation and streaming potentials, both of which were influenced by the evaporation enthalpy (Ee) or vapor pressure. Generally, a higher Ee or lower vapor pressure led to a lower evaporation potential and subsequently a lower Voc. A dual mechanism involving synergistic evaporation potential and streaming potential is proposed to explain the mechanism of NWEGs.

K-guided selective regulation mechanism for CO2 hydrogenation over Ni/CeO2 catalyst.

Regulating the selectivity between CO and CH4 during CO2 hydrogenation is a challenging research topic. Previous research has indicated that potassium (K) modification can adjust the product selectivity by regulating the adsorption strength of formate/CO* intermediates. Going beyond the regulation mechanism described above, this study proposes a K-guided selectivity control method based on the regulation of key intermediates HCO*/H3CO* for Ni catalysts supported on reducible carrier CeO2. By incorporating K, the CO selectivity of CO2 hydrogenation shifts from around 25.4% for Ni/CeO2 to approximately 93.8% for Ni/CeO2-K. This can be attributed to K modification causes electron aggregation in the bonding regions of HCO* and H3CO* intermediates, thus enhancing their adsorption strength. Consequently, the reaction pathway from HCO*/H3CO* to CH4 is limited, favoring the decomposition of formates to CO products. Moreover, the addition of K leads to a moderate decrease in CO2 conversion from 55.2% to 48.6%, which still surpasses values reported in most other studies. This reduction is associated with a decline in reducible Ni species and oxygen vacancy concentration in Ni/CeO2-K. As a result, the adsorption capacity for CO2 and H2 reduces, ultimately reducing CO2 hydrogenation activity.

Resistance matching materials nanoarchitectonics for better performances in water evaporation-driven generators.

The improvement of electricity production for water evaporation-driven generators (WEGs) remains a challenge. Herein, two types of WEGs were designed to study the resistance matching for improving the electricity production using the method of nanoarchitectonics. One type of reduced graphene oxide/carbon nanotube (RGO/CNT) WEG was constructed using RGO with adjustable resistances as working material and CNTs with fixed resistance as electrode material. The other type of graphene oxide (GO)/RGO WEG was constructed using RGO with adjustable resistance as electrode material and GO with fixed resistance was used as working material. The open circuit voltage of RGO/CNT increased from 15 to 56 mV and then decreased to 22 mV with increasing RGO resistance. The short circuit current of RGO/CNT also first increased and then decreased. The performance of GO/RGO was similar with that of RGO/CNT. Typically, the RGO/CNT and GO/RGO WEG showed the highest performance when the working material to electrode material resistance ratio was 2272 and 2365, respectively. It showed that the best resistance ratio of working material to electrode material was in the range of 2000-2500, which helped to improve about 2-5 times of electricity efficiency in the WEG. The present work provides a new direction for optimizing performance of WEGs.

Three-Phase Electrolysis by Gold Nanoparticle on Hydrophobic Interface for Enhanced Electrochemical Nitrogen Reduction Reaction.

Electrochemical nitrogen reduction reaction (NRR) provides a facile and sustainable strategy to produce ammonia (NH3) at ambient conditions. However, the low NH3 yield and Faradaic efficiency (FE) are still the main challenges due to the competitive hydrogen evolution reaction (HER). Herein, a three-phase electrocatalyst through in situ fabrication of Au nanoparticles (NPs) located on hydrophobic carbon fiber paper (Au/o-CFP) is designed. The hydrophobic CFP surface facilitates efficient three-phase contact points (TPCPs) for N2 (gas), electrolyte (liquid), and Au NPs (solid). Thus, concentrated N2 molecules can contact the electrocatalyst surface directly, inhibiting the HER since the lowered proton concentration and overall enhancing NRR. The three-phase Au/o-CFP electrocatalyst presents an excellent NRR performance with high NH3 yield rate of 40.6 µg h-1 mg-1 at -0.30 V and great FE of 31.3% at -0.10 V versus RHE (0.1 m Na2SO4). The N2-bubble contact angle result and cyclic voltammetry analysis confirm that the hydrophobic interface has a relatively strong interaction with N2 bubble for enhanced NRR and weak electrocatalytic activity for HER. Significantly, the three-phase Au/o-CFP exhibits excellent stability with a negligible fluctuation of NH3 yield and FE in seven-cycle test. This work provides a new strategy for improving NRR and simultaneously inhibiting HER.

Plasmonic nanoparticle-film-assisted photoelectrochemical catalysis across the entire visible-NIR region.

Low solar light absorption and high electron-hole pair recombination are still the main challenges for solar energy conversion. Here, we design a plasmonic nanoparticle (NP)-film with a unique structure combining the advantages of a Au NP and film, which exhibits strong broadband absorption from the visible to near-infrared (NIR) wavelength range. In addition, the high density of sub-1 nm inter-particle gaps in the Au NP-film supports electromagnetic field enhancement of several orders of magnitude that greatly promotes the generation and separation of electron-hole pairs. Accordingly, the plasmonic NP-film-assisted photocatalyst (TiO2/90Au/TiO2) leads to an 88-fold increase in the photocurrent density at 0.75 V vs. RHE in 25% methanol solution under visible-NIR light irradiation (λ > 420 nm) compared to a TiO2 film, which is higher than those of the ever reported Au/TiO2 photocatalysts in the entire visible-NIR range. Our finding indicates a promising way to explore full solar spectrum photocatalysts, which can be easily extended to other energy conversion applications.

Self-assembly of carbon nanotube polyhedrons inside microchannels.

Well-defined carbon polyhedrons with faceted morphologies and hollow internal structures made of self-organized multi-walled carbon nanotubes have been fabricated by gas phase catalytic CVD inside microchannels, of which the confined space is critical for the formation of polyhedral structures with hexagonal, heptagonal and octagonal cross-sections that show superhydrophobic properties, with the contact angle up to 162 degrees .

Water-assisted fabrication of aligned microsized carbon tubes made of self-assembled multi-wall carbon nanotubes.

Aligned micro-sized carbon tubes have been successfully synthesized on silicon substrate by pyrolysis of cyclohexane/ferrocene in the presence of water, a spectacular feature of which is that the multi-wall carbon nanotubes formed in situ act as the basic building blocks for the construction of micro-tubes via a "multi-scale" self-assembly process.