Tungsten carbide nanoparticle-encased graphite-like mesoporous carbon (WC/MG), as a precious metal- free cathode catalyst for oxygen reduction reaction, was successfully synthesized by a template replicating-assisted chemical vapor deposition (CVD) method. The obtained mesostructured WC/MG composite possesses high oxygen reduction reaction catalytic activity and stable electrochemical property. In O₂-staturated 0.1 mol/L KOH solution, the half-wave potential (E_1/2) and limiting current density of the sample WC/MG-900 annealed at 900℃ were only 50 mV and 0.2 mA/cm² lower than those of commercial Pt/C catalyst, respectively. Koutecky-Levich (K-L) plots and rotating ring-disk electrode (RDE) measurements indicated that the mesostructured WC/MG exhibited an approximate 4 e^- transfer pathway during the ORR process. The comparable ORR performance to Pt/C, long-lived electrochemical stability and excellent methanol tolerance make the synthesized mesostructured WC/MG composite a potential electrode catalyst in oxygen reduction reaction.

Interface stability is one of the key issues determining the service reliability and life of thermoelectric devices. For skutterudite-based thermoelectric devices, the barrier layer is required in order to restrain the inter-diffusion between the hot-side electrode and skutterudite matrix. In this work, Ti₈₈Al₁₂ was selected as the barrier layer. N-type Yb_0.3Co₄Sb₁₂/Ti₈₈Al₁₂/Yb_0.3Co₄Sb₁₂ and p-type CeFe_3.85Mn_0.15Sb₁₂/Ti₈₈Al₁₂/CeFe_3.85Mn_0.15Sb₁₂ thermoelectric joints were prepared by one-step hot pressing sintering method. The evolution processes of contact resistivity and microstructure were studied through accelerated aging experiments. The results show that the contact resistivity of n-type joints increases slower than that of p-type joints under the same aging condition. Activation energy for n-type and p-type joints is 84.1 kJ/mol and 68.8 kJ/mol, respectively. Growth of the inter-metallic compound layer and cracking at the AlCo/TiCoSb interface result in rapidly increased contact resistivity of n-type joints. For p-type joints, the difference of coefficient of thermal expansion between CeFe_3.85Mn_0.15Sb₁₂ and Ti₈₈Al₁₂ becomes the main reason for the cracks.

TiO₂ is frequently used as electron transport layer in perovskite solar cells, and its structure can directly affect the performance of MAPbBr₃ solar cells. It is necessary to investigate the structural effect of TiO₂ to further understand the working mechanism of such kind solar cells. TiO₂ thin films with different morphology were prepared by spin coating, and MAPbBr₃ (MA = CH₃NH₃) thin films were further deposited on it through anti-solvent assisted crystallization approach. Then, energy band alignment between TiO₂ and MAPbBr₃ were characterized by X-ray photoelectron spectroscopy (XPS). According to the experimental results, TiO₂ with different morphology possessed different electronic structures and yield different band alignment after contacting with MAPbBr₃ perovskite layer. The difference of conduction band value between TiO₂ and MAPbBr₃ can directly affect the transport and collection feature of electrons, thereby governing the performance of the photovoltaic device.

Photoelectrochemical (PEC) water splitting provides a “green” approach for hydrogen production. Photoanodes for water oxidation reactions are the bottleneck for PEC water splitting due to the involved thermodynamic and kinetic challenges. To obtain the target of 10% solar-to-hydrogen (STH) efficiency toward practical applications, efficient photoanodes should be developed. Owing to the intrinsic advantages of low cost, good light harvesting, low toxicity, and excellent (photo)-electrochemical stability, visible light responsive metal oxides such as WO₃, α-Fe₂O₃ and BiVO₄ have attracted great attention for potential photoanodes and significant achievements have been made in the past decades. In this review, the sate-of-the-art progresses of WO₃, α-Fe₂O₃ and BiVO₄ photoanodes are summarized with an emphasis on the rational materials design toward efficient PEC water splitting. Moreover, their applications in unassisted PEC water splitting systems are briefly introduced. The perspectives on the challenges and future development of visible light responsive metal oxide photoanodes are presented.

A novel graphene aerogel with pore size less than 1 µm was synthesized by Sol-Gel method, in which Nafion was skillfully introduced as modifiers connecting graphene oxides (GO). Ethylenediamine was used to produce a chemically linked graphene hydrogel during reducing process, which can then be freeze-dried to remove the absorbed water to form graphene aerogel. Nafion in GO solution prohibits the re-stacking of individual graphene sheets during reduction and freeze-drying process. By the above method, the pore size of as-prepared graphene aerogel could be effectively controlled within 1 µm, much less than that of the traditional graphene aerogel (20- 100 µm). The new graphene aerogel with unique structure exhibited excellent properties, such as high specific surface area, high porosity, and better electrochemical properties. All data suggest that this graphene aerogel may have promising application prospect in the field of energy.

Recovering Si material from the degraded solar cells is significant for environmental protection and material recycling. In this tudy, the optimal conditions for recycling degraded solar cells by chemical etching and ultrasonic cleaning were investigated. The samples were tested by EDS, SEM and XPS, The results showed that Al electrodes were completely removed from cells by reaction with 10wt% NaOH solution for 18 min, with less silicon corrosion lost. After that, Ag electrodes were completely exfoliated from the cells by ultrasonic cleaning (40 kHz) for 20 min. Si₃N₄ film was thoroughly eliminated after the cells were etched with 40wt% HF solution for 10 min, which was proved to be the optimal reaction time. A quantitative experiment was performed in this study with 8. 9068 g cells. The results show that the recycling mass of Al electrodes, Ag electrodes and Si wafers are 1.1102 g, 0.0766 g and 7.7169 g, respectively.

This paper reported on the fabrication of tri-layered oxygen transport membranes, “porous|dense|porous” Zr_0.84Y_0.16O_2-δ-La_0.8Sr_0.2Cr_0.5Fe_0.5O_3-δ (YSZ-LSCF), by the tape casting, tape lamination and co-firing techniques. Catalytically active nano-scale particles of LaNi_0.6Fe_0.4O_3-δ (LNF) were impregnated into the porous scaffolds. In order to quantatively determine the resistances of the oxygen reduction or evolution reactions against oxygen permeation, an additional dense YSZ layer was introduced inside the dense YSZ-LSCF permeation layer. Electrochemical measurements on the resulting five-layered solid oxide fuel cells showed a large reduction in the interfacial polarization resistances at the presence of these LNF catalysts, with the lowest values observed at the LNF loadings of 12wt%. In particular, the cathodic and anodic polarization resistances were 0.26 and 0.08 Ω·cm² at 800℃, respectively. The oxygen permeation flux under the air/CH₄ gradient was 7.6 mL/(cm²·min), which was 14 times higher than the measured value for the blank YSZ-LSCF membrane. Further impedance analysis indicated that the charge transfer step during oxygen reduction may limit the overall oxygen permeation process.

Quantum dots sensitized solar cells (QDSCs) play a key role in the new generation photovoltaic devices due to their low cost and easy fabrication process. The absorption spectrum of quantum dots can be tailored by controlling grain size, and multi-exaction generation. QDSCs using inorganic compound QDs replaces the dye as a sensitizer, which is able to solve the stability of the dye sensitized solar cells. However, further improvement of the conversion efficiency of QDSCs is still a major issue for their application. Recently, tailoring electronic properties of the counter electrode(CE) in QDSCs using different materials has been considered as a promising way to improve photovoltaic performance of QDSCs. This article reviewed the quite recent progress of CE in QDSCs based on synthesis method, surface microtopography and crystal structure. This review gave a panorama of metal chalcogenides, composite materials, hybrid materials, muti-component metal chalcogenides, conductive polymers, and carbon CE materials for QDSCs, while the influence of CE materials on the charge transfer impedance, the electron transport process, catalytic properties, and I-V characteristics was stressed in detail. Finally, an outlook on the future challenges and prospects of novel materials as the CE for QDSCs were also briefly put forward.

The quercus variabilis cork made up of cavity cells is used as raw material. Herein, the cork-derived activated carbon with the various pores was successfully prepared by the facile carbonization of cork followed by chemical activation. The as-prepared activated carbon sheets possess large specific surface area (2312 m ²/g) and unique interconnected pores. As a result, it shows excellent electrochemical performance as electrode material for supercapacitors. In three electrode system of KOH, it exhibits a high specific capacitance of 296 F/g at a current density of 0.1 A/g. The assembled symmetric supercapacitor shows a high specific capacitance of 201 F/g at 5 A/g, with a good cycling stability of 99.5 % capacitance retention after 5000 cycles. In two electrode system of Na₂SO₄, the symmetric supercapacitor displays a good rate performance of 80.5% retention from 0.5 A/g (174 F/g) to 50 A/g (140 F/g) and a high energy density of 19.62 Wh/kg.

A novel nickel molybdate/mutiwalled carbon nanotubes (NiMoO₄/MWCNTs) composite was synthesized by hydrothermal method using nickel nitrate, sodium molybdate and MWCNTs as raw materials, and the product was characterized by scanning electronic microscopy, energy dispersive spectra, and X-ray diffraction spectra. The scanning electron microscopy results showed that pseudo-spherical NiMoO₄ was wrapped with MWCNTs and all elements were uniformly distributed in the material. Cyclic voltammetry and electrochemical impedance spectra revealed that the presence of MWCNTs greatly improved the redox signal and electron transfer kinetics of NiMoO₄. The capacitance tests further indicated that the composite presented better specific capacitance, rate capability, and cycling stability than the single-component of NiMoO₄, and with a MWCNTs content of 40 mg the composite (NiMoO₄/MWCNTs-40) displayed the best electrochemical performance. At the current density of 2 A/g, the NiMoO₄/MWCNTs-40 composite demonstrated a remarkable specific capacitance of 1071 F/g; while current density was increased to 10 A/g and the capacitance still remained 66.10%. Cyclic stability experiment revealed that the NiMoO₄/MWCNTs-40 composite retained 95.85% of its initial specific capacitance after 2500 charge-discharge cycles at a current density of 10 A/g, exhibiting prominent electrochemical stability.

Nanostructured NiCo₂S₄ films on Ni foams were successfully synthesized through a facile method, involving hydrothermal growth of NiCo-precursor and subsequent sulfidation process of NiCo₂S₄. The influence of different surfactants were investigated, including morphology, phase structure and electrochemical performance of NiCo₂S₄ electrodes. With the addition of surfactants during the hydrothermal processes, the nanostructured NiCo₂S₄ self-organized and agglomerated into nanosheets, showing outstanding influence on the morphology by the surfactants. Among these electrodes, the NiCo₂S₄ electrode modified with SDS exhibited an optimal capacitance of 2893 F/g at 0.5 A/g, a superior rate capability of 1890.6 F/g even at 10 A/g, and good cycling stability of 96.1% over 1000 cycles. These results indicate that nanosheet NiCo₂S₄ would be promising electrode materials for supercapacitor applications.