In Situ Engineering of Intracellular Hemoglobin for Implantable High-Performance Biofuel Cells.

The key challenge for the broad application of implantable biofuel cells (BFCs) is to achieve inorganic-organic composite biocompatibility while improving the activity and selectivity of the catalysts. We have fabricated nanoengineered red blood cells (NERBCs) by an environmentally friendly method by using red blood cells as the raw material and hemoglobin (Hb) embedded with ultrasmall hydroxyapatite (HAP, Ca10 (PO4 )6 (OH)2 ) as the functional BFC cathode material. The NERBCs showed greatly enhanced cell performance with high electrocatalytic activity, stability, and selectivity. The NERBCs maintained the original biological properties of the natural cell, while enhancing the catalytic oxygen reduction reaction (ORR) through the interaction between -OH groups in HAP and the Hb in RBCs. They also enabled direct electron transportation, eliminating the need for an electron-transfer mediator, and showed catalytic inactivity for glucose oxidation, thus potentially enabling the development of separator-free BFCs.

Lithiation-Induced Non-Noble Metal Nanoparticles for Li-O2 Batteries.

Low-cost and highly active electrocatalysts are attractive for Li-O2 applications. Herein, a 3D interconnected plate architecture consisting of ultrasmall Co-Ni grains embedded in lithium hydroxide nanoplates (Co2Ni@LiOH) is designed and prepared by a lithiation strategy at room temperature. This catalyst exhibits a remarkably reduced charge potential of ∼3.4 V at 50 µA cm-2, which leads to the high roundtrip efficiency of ∼79%, among the best levels reported and a cycle life of up to 40 cycles. The well-aligned network facilitates the oxygen diffusion and the electrolyte penetration into the electrode. The enhanced electrical conductivity network improves the charge transport kinetics and more active sites are exposed, which facilitate the adsorption and dissociation of oxygen during the oxygen reduction reaction and the oxygen evolution reaction. This new catalyst design inspires the development of an effective non-noble metal catalyst for Li-O2 batteries.

Atomically Thin Mesoporous Co3 O4 Layers Strongly Coupled with N-rGO Nanosheets as High-Performance Bifunctional Catalysts for 1D Knittable Zinc-Air Batteries.

Under development for next-generation wearable electronics are flexible, knittable, and wearable energy-storage devices with high energy density that can be integrated into textiles. Herein, knittable fiber-shaped zinc-air batteries with high volumetric energy density (36.1 mWh cm-3 ) are fabricated via a facile and continuous method with low-cost materials. Furthermore, a high-yield method is developed to prepare the key component of the fiber-shaped zinc-air battery, i.e., a bifunctional catalyst composed of atomically thin layer-by-layer mesoporous Co3 O4 /nitrogen-doped reduced graphene oxide (N-rGO) nanosheets. Benefiting from the high surface area, mesoporous structure, and strong synergetic effect between the Co3 O4 and N-rGO nanosheets, the bifunctional catalyst exhibits high activity and superior durability for oxygen reduction and evolution reactions. Compared to a fiber-shaped zinc-air battery using state-of-the-art Pt/C + RuO2 catalysts, the battery based on these Co3 O4 /N-rGO nanosheets demonstrates enhanced and stable electrochemical performance, even under severe deformation. Such batteries, for the first time, can be successfully knitted into clothes without short circuits under external forces and can power various electronic devices and even charge a cellphone.

Textile Inspired Lithium-Oxygen Battery Cathode with Decoupled Oxygen and Electrolyte Pathways.

The lithium-air (Li-O2 ) battery has been deemed one of the most promising next-generation energy-storage devices due to its ultrahigh energy density. However, in conventional porous carbon-air cathodes, the oxygen gas and electrolyte often compete for transport pathways, which limit battery performance. Here, a novel textile-based air cathode is developed with a triple-phase structure to improve overall battery performance. The hierarchical structure of the conductive textile network leads to decoupled pathways for oxygen gas and electrolyte: oxygen flows through the woven mesh while the electrolyte diffuses along the textile fibers. Due to noncompetitive transport, the textile-based Li-O2 cathode exhibits a high discharge capacity of 8.6 mAh cm-2 , a low overpotential of 1.15 V, and stable operation exceeding 50 cycles. The textile-based structure can be applied to a range of applications (fuel cells, water splitting, and redox flow batteries) that involve multiple phase reactions. The reported decoupled transport pathway design also spurs potential toward flexible/wearable Li-O2 batteries.

Synergetic Effect of Ti3+ and Oxygen Doping on Enhancing Photoelectrochemical and Photocatalytic Properties of TiO2/g-C3N4 Heterojunctions.

To improve the utilization of visible light and reduce photogenerated electron/hole recombination, Ti3+ self-doped TiO2/oxygen-doped graphitic carbon nitride (Ti3+-TiO2/O-g-C3N4) heterojunctions were prepared via hydrothermal treatment of a mixture of g-C3N4 and titanium oxohydride sol obtained from the reaction of TiH2 with H2O2. In this way, exfoliated O-g-C3N4 and Ti3+-TiO2 nanoparticles were obtained. Simultaneously, strong bonding was formed between Ti3+-TiO2 nanoparticles and exfoliated O-g-C3N4 during the hydrothermal process. Charge transfer and recombination processes were characterized by transient photocurrent responses, electrochemical impedance test, and photoluminescence spectroscopy. The photocatalytic performances were investigated through rhodamine B degradation test under an irradiation source based on 30 W cold visible-light-emitting diode. The highest visible-light photoelectrochemical and photocatalytic activities were observed from the heterojunction with 1:2 mass ratio of Ti3+-TiO2 to O-g-C3N4. The photodegradation reaction rate constant based on this heterojuction is 0.0356 min-1, which is 3.87 and 4.56 times higher than those of pristine Ti3+-TiO2 and pure g-C3N4, respectively. The remarkably high photoelectrochemical and photocatalytic performances of the heterojunctions are mainly attributed to the synergetic effect of efficient photogenerated electron-hole separation, decreased electron transfer resistance from interfacial chemical hydroxy residue bonds, and oxidizing groups originating from Ti3+-TiO2 and O-g-C3N4.

Z-Scheme NiTiO3/g-C3N4 Heterojunctions with Enhanced Photoelectrochemical and Photocatalytic Performances under Visible LED Light Irradiation.

Direct Z-scheme NiTiO3/g-C3N4 heterojunctions were successfully assembled by using simple calcination method and the photoelectrochemical and photocatalytic performance were investigated by light emitting diode (LED). The photoanode composed by the heterojunction with about 50 wt % NiTiO3 content exhibits the best photoelectrochemical activity with photoconversion efficiency up to 0.066%, which is 4.4 and 3.13 times larger than NiTiO3 or g-C3N4. The remarkably enhanced photoelectrochemical and photocatalytic activity of the heterojunction can be due to the efficiently photogenerated electron-hole separation by a Z-scheme mechanism.

Sn Nanoparticles Encapsulated in 3D Nanoporous Carbon Derived from a Metal-Organic Framework for Anode Material in Lithium-Ion Batteries.

Three-dimensional nanoporous carbon frameworks encapsulated Sn nanoparticles (Sn@3D-NPC) are developed by a facile method as an improved lithium ion battery anode. The Sn@3D-NPC delivers a reversible capacity of 740 mAh g-1 after 200 cycles at a current density of 200 mA g-1, corresponding to a capacity retention of 85% (against the second capacity) and high rate capability (300 mAh g-1 at 5 A g-1). Compared to the Sn nanoparticles (SnNPs), such improvements are attributed to the 3D porous and conductive framework. The whole structure can provide not only the high electrical conductivity that facilities the electron transfer but also the elasticity that will suppress the volume expansion and aggregation of SnNPs during the charge and discharge process. This work opens a new application of metal-organic frameworks in energy storage.

Regulating the spatial distribution of metal nanoparticles within metal-organic frameworks to enhance catalytic efficiency.

Composites incorporating metal nanoparticles (MNPs) within metal-organic frameworks (MOFs) have broad applications in many fields. However, the controlled spatial distribution of the MNPs within MOFs remains a challenge for addressing key issues in catalysis, for example, the efficiency of catalysts due to the limitation of molecular diffusion within MOF channels. Here we report a facile strategy that enables MNPs to be encapsulated into MOFs with controllable spatial localization by using metal oxide both as support to load MNPs and as a sacrificial template to grow MOFs. This strategy is versatile to a variety of MNPs and MOF crystals. By localizing the encapsulated MNPs closer to the surface of MOFs, the resultant MNPs@MOF composites not only exhibit effective selectivity derived from MOF cavities, but also enhanced catalytic activity due to the spatial regulation of MNPs as close as possible to the MOF surface.

Electrochemical Doping of Halide Perovskites with Ion Intercalation.

Halide perovskites have recently been investigated for various solution-processed optoelectronic devices. The majority of studies have focused on using intrinsic halide perovskites, and the intentional incoporation of dopants has not been well explored. In this work, we discovered that small alkali ions, including lithium and sodium ions, could be electrochemically intercalated into a variety of halide and pseudohalide perovskites. The ion intercalation caused a lattice expansion of the perovskite crystals and resulted in an n-type doping of the perovskites. Such electrochemical doping improved the conductivity and changed the color of the perovskites, leading to an electrochromism with more than 40% reduction of transmittance in the 450-850 nm wavelength range. The doped perovskites exhibited improved electron injection efficiency into the pristine perovskite crystals, resulting in bright light-emitting diodes with a low turn-on voltage.

Kinetic Study of Parasitic Reactions in Lithium-Ion Batteries: A Case Study on LiNi(0.6)Mn(0.2)Co(0.2)O2.

The side reactions between the electrode materials and the nonaqueous electrolytes have been the major contributor to the degradation of electrochemical performance of lithium-ion batteries. A home-built high-precision leakage current measuring system was deployed to investigate the reaction kinetics between the delithiated LiNi(0.6)Mn(0.2)Co(0.2)O2 and a conventional nonaqueous electrolyte. It was found that the rate of parasitic reaction had strong dependence on the upper cutoff potential of the cathode material. The kinetic data also indicated a change of reaction mode at about 4.5 V vs Li(+)/Li.

Networks of ultrasmall Pd/Cr nanowires as high performance hydrogen sensors.

The newly developed hydrogen sensor, based on a network of ultrasmall pure palladium nanowires sputter-deposited on a filtration membrane, takes advantage of single palladium nanowires' characteristics of high speed and sensitivity while eliminating their nanofabrication obstacles. However, this new type of sensor, like the single palladium nanowires, cannot distinguish hydrogen concentrations above 3%, thus limiting the potential applications of the sensor. This study reports hydrogen sensors based on a network of ultrasmall Cr-buffered Pd (Pd/Cr) nanowires on a filtration membrane. These sensors not only are able to outperform their pure Pd counterparts in speed and durability but also allow hydrogen detection at concentrations up to 100%. The new networks consist of a thin layer of palladium deposited on top of a Cr adhesion layer 1-3 nm thick. Although the Cr layer is insensitive to hydrogen, it enables the formation of a network of continuous Pd/Cr nanowires with thicknesses of the Pd layer as thin as 2 nm. The improved performance of the Pd/Cr sensors can be attributed to the increased surface area to volume ratio and to the confinement-induced suppression of the phase transition from Pd/H solid solution (α-phase) to Pd hydride (ß-phase).