Kun Liang

Enhanced Photoelectrocatalytic Reduction of Oxygen Using Au@TiO2 Plasmonic Film

Novel Au@TiO2 plasmonic films were fabricated by individually placing Au nanoparticles into TiO2 nanocavity arrays through a sputtering and dewetting process. These discrete Au nanoparticles in TiO2 nanocavities showed strong visible-light absorption due to the plasmonic resonance. Photoelectrochemical studies demonstrated that the developed Au@TiO2 plasmonic films exhibited significantly enhanced catalytic activities toward oxygen reduction reactions with an onset potential of 0.92 V (vs reversible hydrogen electrode), electron transfer number of 3.94, and limiting current density of 5.2 mA cm-2. A superior ORR activity of 310 mA mg-1 is achieved using low Au loading mass. The isolated Au nanoparticle size remarkably affected the catalytic activities of Au@TiO2, and TiO2 coated with 5 nm Au (Au5@TiO2) exhibited the best catalytic function to reduce oxygen. The plasmon-enhanced reductive activity is attributed to the surface plasmonic resonance of isolated Au nanoparticles in TiO2 nanocavities and suppressed electron recombination. This work provides comprehensive understanding of a novel plasmonic system using isolated noble metals into nanostructured semiconductor films as a potential alternative catalyst for oxygen reduction reaction.

Periodically Patterned Au-TiO2 Heterostructures for Photoelectrochemical Sensor

Periodically patterned Au nanorods in TiO2 nanocavities (Au NRs@TiO2) were fabricated via magnetron sputtering followed by a thermal dewetting process. This innovative Au NRs@TiO2 heterostructure was used as a plasmonic sensing platform for photoelectrochemical detection of glucose and lactose. This Au NRs@TiO2 patterned heterostructure possesses superior sensing properties to other Au nanoparticle-based sensors because (i) localized surface plasmon resonance (LSPR) generated at Au/TiO2 interfaces enhanced sensitivity of glucose (lactose) amperometric detection; (ii) periodic Au nanocrystals in TiO2 nanocavities accelerated charge separation and transfer rate, especially under monochromatic blue light irradiation; (iii) discrete planar architectures comprising Au NRs immobilized on TiO2 substrates significantly improved stability and reusability of the sensors. A low detection limit of 1 μM (10 μM) and a high sensitivity of 812 μA mM-1 cm-2 (270 μA mM-1 cm-2) were achieved on the Au NRs@TiO2 heterostructures for glucose (lactose) detection without the addition of enzymes. Good selectivity and superb stability over more than 8 weeks was also demonstrated using these Au NRs@TiO2 heterostructures for glucose (lactose) detection. Additionally, this cost-efficient technique can be easily extended to other photoelectrochemical sensing systems when considering the combination of sensing and visible or infrared light source enhancement.

Freestanding NiFe Oxyfluoride Holey Film with Ultrahigh Volumetric Capacitance for Flexible Asymmetric Supercapacitors

In this work, a freestanding NiFe oxyfluoride (NiFeOF) holey film is prepared by electrochemical deposition and anodic treatments. With the combination of good electrical conductivity and holey structure, the NiFeOF holey film offers superior electrochemical performance with maximum specific capacitance of 670 F cm-3 (134 mF cm-2 ), due to the following reasons: (i) The residual metal alloy framework can be used as the current collector to improve electrode conductivity. Moreover, the as-prepared freestanding NiFeOF holey film can be used as a supercapacitor electrode without reliance on binders and other additives. The residual metal alloy framework and binder-free electrode effectively reduce electrode resistance, thus improving electron transport. (ii) The highly interconnected holey structure and hierarchical pore distribution provide a high specific surface area to improve electron transport, enhancing rapid ion transport, and mitigating diffusion limitations throughout the holey film. (iii) The excellent mechanical characteristics facilitate flexibility and cyclability related performance. Additionally, the NiFeOF holey film presents exceptional electrochemical performance, showing that it is a promising alternative for small/microsize electronic devices.

Facile preparation of a high-quality copper layer on epoxy resin via electroless plating for applications in electromagnetic interference shielding

A convenient and low-cost approach to fabricate a high-quality copper layer on epoxy resin via electroless plating for applications in electromagnetic interference (EMI) shielding is introduced in this paper. Through the surface modification of thiosulfate (S2O32−), an epoxy resin substrate is able to adsorb silver ions, which could create a catalytic activating layer to catalyze the subsequent electroless copper plating (ECP) of a conductive deposited copper layer at low temperature. The effects of thiosulfate are evaluated based on water contact angle measurement, XPS, FT-IR, SEM, EDS and adhesion tests. The incorporation of thiosulfate effectively modifies the epoxy resin substrate surface, thus promoting adhesion between the epoxy resin and the deposited copper layer. Moreover, after 40 min of ECP, the resulting deposited copper layer presents a low resistivity of 2.24 × 10−6 Ω cm and an excellent electromagnetic interference shielding effectiveness of greater than 60 dB in the frequency range from 4 GHz to 18 GHz. It can be concluded that the developed technology can be used to enable surface metallization of epoxy resin as a highly effective electromagnetic interference shielding material without the use of high temperatures or sophisticated manufacturing equipment.

Nickel Sulfide Freestanding Holey Films as Air-Breathing Electrodes for Flexible Zn–Air Batteries

In this work, a combination of bottom-up electrochemical deposition and top-down electrochemical etching strategies followed by a subsequent sulfuration treatment was employed to rationally synthesize a nickel sulfide (NiS x) freestanding holey film (FHF). Owing to the holey structure along with the optimal electrochemically active surface area and active sites, the as-prepared NiS x FHF showed an impressive bifunctional electrocatalytic performance toward both oxygen evolution and reduction reactions. The holey and freestanding features provide the NiS x FHF with promising characteristics to be used as an ideal air-breathing cathode in flexible Zn-air batteries (ZABs). As a proof-of-concept, the rationally designed NiS x FHF achieved remarkable rechargeability and flexibility in a ZAB configuration.