A tri-functional self-supported electrocatalyst featuring mostly NiTeO perovskite for H production methanol-water co-electrolysis.

A self-supported NiTeO perovskite is made by deploying an extended hydrothermal tellurization strategy with a restricted Te content, which was found to be exceptionally active towards the oxidation of water and methanol and the reduction of water in 1.0 M KOH where it delivered -10 mA cm at just -1.54 V for a full cell featuring MOR‖HER.

Ambiguities and best practices in the determination of active sites and real surface area of monometallic electrocatalytic interfaces.

Determining the number of electrocatalytically accessible sites (ECAS) and real surface area (RSA) for any given electrocatalyst precisely is important in energy conversion electrocatalysis as these are directly used in the determination of intrinsic activity markers. For monometallic electrocatalysts and electrocatalysts of just one type of active site, there believed to be ways of making precise determination of ECAS and RSA using underpotential deposition (UPD), stripping, and redox-charge integration employing transient voltammetric sweeping techniques. This transient nature of sweeping techniques makes the determination of ECAS and RSA relatively less reliable.

The Significance of Properly Reporting Turnover Frequency in Electrocatalysis Research.

For decades, turnover frequency (TOF) has served as an accurate descriptor of the intrinsic activity of a catalyst, including those in electrocatalytic reactions involving both fuel generation and fuel consumption. Unfortunately, in most of the recent reports in this area, TOF is often not properly reported or not reported at all, in contrast to the overpotentials at a benchmarking current density. The current density is significant in determining the apparent activity, but it is affected by catalyst-centric parasitic reactions, electrolyte-centric competing reactions, and capacitance.

Strategies and Perspectives to Catch the Missing Pieces in Energy-Efficient Hydrogen Evolution Reaction in Alkaline Media.

Transition metal hydroxides (M-OH) and their heterostructures (X|M-OH, where X can be a metal, metal oxide, metal chalcogenide, metal phosphide, etc.) have recently emerged as highly active electrocatalysts for hydrogen evolution reaction (HER) of alkaline water electrolysis. Lattice hydroxide anions in metal hydroxides are primarily responsible for observing such an enhanced HER activity in alkali that facilitate water dissociation and assist the first step, the hydrogen adsorption.

A review on recent developments in electrochemical hydrogen peroxide synthesis with a critical assessment of perspectives and strategies.

Electrochemical hydrogen peroxide synthesis using two-electron oxygen electrochemistry is an intriguing alternative to currently dominating environmentally unfriendly and potentially hazardous anthraquinone process and noble metals catalysed direct synthesis. Electrocatalytic two-electron oxygen reduction reaction (ORR) and water oxidation reaction (WOR) are the source of electrochemical hydrogen peroxide generation. Various electrocatalysts have been used for the same and were characterized using several electroanalytical, chemical, spectroscopic and chromatographic tools.

Ultrafast Growth of a Cu(OH)-CuO Nanoneedle Array on Cu Foil for Methanol Oxidation Electrocatalysis.

A swift potentiostatic anodization method for growing a 5-7 μm tall nanoneedle array of Cu(OH)-CuO on Cu foil within 100 s has been developed. This catalytic electrode when screened for methanol oxidation electrocatalysis in 1 M KOH with 0.5 M methanol, delivered a current density as high as 70 ± 10 mA cm at 0.

All-Soft Supercapacitors Based on Liquid Metal Electrodes with Integrated Functionalized Carbon Nanotubes.

Soft energy storage devices, such as supercapacitors, are an essential component for powering integrated soft microsystems. However, conventional supercapacitors are mainly manufactured using hard/brittle materials that easily crack and eventually delaminate from the current collector by mechanical deformation. Therefore, to realize all-soft supercapacitors, the electrodes should be soft, stretchable, and highly conductive without compromising the electrochemical performance.

Amorphous Catalysts and Electrochemical Water Splitting: An Untold Story of Harmony.

In the near future, sustainable energy conversion and storage will largely depend on the electrochemical splitting of water into hydrogen and oxygen. Perceiving this, countless research works focussing on the fundamentals of electrocatalysis of water splitting and on performance improvements are being reported everyday around the globe. Electrocatalysts of high activity, selectivity, and stability are anticipated as they directly determine energy- and cost efficiency of water electrolyzers.

Gd-Enhanced Growth of Multi-Millimeter-Tall Forests of Single-Wall Carbon Nanotubes.

Multi-millimeter-tall vertically aligned single-wall carbon nanotube (VA-SWCNT) forests were grown using Fe/Gd/AlO catalyst with high initial growth rate of ∼2 μm s and long catalyst lifetime of ∼70 min at 800 °C. The addition of Gd with a nominal thickness of 0.3 nm drastically prolonged the catalyst lifetime.

Effective Heat Transfer Pathways of Thermally Conductive Networks Formed by One-Dimensional Carbon Materials with Different Sizes.

We investigated the heat transfer behavior of thermally conductive networks with one-dimensional carbon materials to design effective heat transfer pathways for hybrid filler systems of polymer matrix composites. Nano-sized few-walled carbon nanotubes (FWCNTs) and micro-sized mesophase pitch-based carbon fibers (MPCFs) were used as the thermally conductive materials. The bulk density and thermal conductivity of the FWCNT films increased proportionally with the ultrasonication time due to the enhanced dispersibility of the FWCNTs in an ethanol solvent.

Enhancing the photovoltaic performance of hybrid heterojunction solar cells by passivation of silicon surface via a simple 1-min annealing process.

Solution-based heterojunction technology is emerging for facile fabrication of silicon (Si)-based solar cells. Surface passivation of Si substrate has been well established to improve the photovoltaic (PV) performance for the conventional bulk Si cells. However, the impact is still not seen for the heterojunction cells.

Carbon Nanotubes and Related Nanomaterials: Critical Advances and Challenges for Synthesis toward Mainstream Commercial Applications.

Advances in the synthesis and scalable manufacturing of single-walled carbon nanotubes (SWCNTs) remain critical to realizing many important commercial applications. Here we review recent breakthroughs in the synthesis of SWCNTs and highlight key ongoing research areas and challenges. A few key applications that capitalize on the properties of SWCNTs are also reviewed with respect to the recent synthesis breakthroughs and ways in which synthesis science can enable advances in these applications.

An interdigitated electrode with dense carbon nanotube forests on conductive supports for electrochemical biosensors.

A highly sensitive interdigitated electrode (IDE) with vertically aligned dense carbon nanotube forests directly grown on conductive supports was demonstrated by combining UV lithography and a low temperature chemical vapor deposition process (470 °C). The cyclic voltammetry (CV) measurements of K4[Fe(CN)6] showed that the redox current of the IDE with CNT forests (CNTF-IDE) reached the steady state much more quickly compared to that of conventional gold IDE (Au-IDE). The performance of the CNTF-IDE largely depended on the geometry of the electrodes (e.

Carbon Nanotube Web with Carboxylated Polythiophene "Assist" for High-Performance Battery Electrodes.

A carbon nanotube (CNT) web electrode comprising magnetite spheres and few-walled carbon nanotubes (FWNTs) linked by the carboxylated conjugated polymer, poly[3-(potassium-4-butanoate) thiophene] (PPBT), was designed to demonstrate benefits derived from the rational consideration of electron/ion transport coupled with the surface chemistry of the electrode materials components. To maximize transport properties, the approach introduces monodispersed spherical FeO (sFeO) for uniform Li diffusion and a FWNT web electrode frame that affords characteristics of long-ranged electronic pathways and porous networks. The sFeO particles were used as a model high-capacity energy active material, owing to their well-defined chemistry with surface hydroxyl (-OH) functionalities that provide for facile detection of molecular interactions.

Self-supporting S@GO-FWCNTs composite films as positive electrodes for high-performance lithium-sulfur batteries.

Although lithium-sulfur (Li-S) batteries are a promising secondary power source, it still faces many technical challenges, such as rapid capacity decay and low sulfur utilization. The loading of sulfur and the weight percentage of sulfur in the cathode usually have a significant influence on the energy density. Herein, we report an easy synthesis of a self-supporting sulfur@graphene oxide-few-wall carbon nanotube (S@GO-FWCNT) composite cathode film, wherein an aluminum foil current collector is replaced by FWCNTs and sulfur particles are uniformly wrapped by graphene oxide along with FWCNTs.

Ten-Second Epitaxy of Cu on Repeatedly Used Sapphire for Practical Production of High-Quality Graphene.

Epitaxial copper (Cu) films yield graphene with superior quality but at high cost. We report 1-3 μm thick epitaxial Cu films prepared on plane sapphire substrates in 10-30 s, which is much faster than that of the typical sputtering method. Such rapid deposition is realized by vapor deposition using a Cu source heated to 1700-1800 °C, which is much higher than its melting point of 1085 °C.

Hierarchical networks of redox-active reduced crumpled graphene oxide and functionalized few-walled carbon nanotubes for rapid electrochemical energy storage.

Crumpled graphene is known to have a strong aggregation-resistive property due to its unique 3D morphology, providing a promising solution to prevent the restacking issue of graphene based electrode materials. Here, we demonstrate the utilization of redox-active oxygen functional groups on the partially reduced crumpled graphene oxide (r-CGO) for electrochemical energy storage applications. To effectively utilize the surface redox reactions of the functional groups, hierarchical networks of electrodes including r-CGO and functionalized few-walled carbon nanotubes (f-FWNTs) are assembled via a vacuum-filtration process, resulting in a 3D porous structure.

Biomass-derived carbonaceous positive electrodes for sustainable lithium-ion storage.

Biomass derived carbon materials have been widely used as electrode materials; however, in most cases, only electrical double layer capacitance (EDLC) is utilized and therefore, only low energy density can be achieved. Herein, we report on redox-active carbon spheres that can be simply synthesized from earth-abundant glucose via a hydrothermal process. These carbon spheres exhibit a specific capacity of ∼210 mA h gCS(-1), with high redox potentials in the voltage range of 2.

Electrochemical polymerization of pyrene derivatives on functionalized carbon nanotubes for pseudocapacitive electrodes.

Electrochemical energy-storage devices have the potential to be clean and efficient, but their current cost and performance limit their use in numerous transportation and stationary applications. Many organic molecules are abundant, economical and electrochemically active; if selected correctly and rationally designed, these organic molecules offer a promising route to expand the applications of these energy-storage devices. In this study, polycyclic aromatic hydrocarbons are introduced within a functionalized few-walled carbon nanotube matrix to develop high-energy, high-power positive electrodes for pseudocapacitor applications.

One-step sub-10 μm patterning of carbon-nanotube thin films for transparent conductor applications.

We propose a technique for one-step micropatterning of as-grown carbon-nanotube films on a plastic substrate with sub-10 μm resolution on the basis of the dry transfer process. By utilizing this technique, we demonstrated the novel high-performance flexible carbon-nanotube transparent conductive film with a microgrid structure, which enabled improvement of the performance over the trade-off between the sheet resistance and transmittance of a conventional uniform carbon-nanotube film. The sheet resistance was reduced by 46% at its maximum by adding the microgrid, leading to a value of 53 Ω/sq at a transmittance of 80%.

Methane-assisted chemical vapor deposition yielding millimeter-tall single-wall carbon nanotubes of smaller diameter.

We examined the use of low purity H2 (96 vol % H2 with 4 vol % CH4) in chemical vapor deposition (CVD) using a C2H2 feedstock, and obtained vertically aligned single-wall carbon nanotubes (VA-SWCNTs) with unexpectedly smaller diameters, larger height, and higher quality compared with those grown using pure H2. During the catalyst annealing, carbon deposited at a small amount from CH4 on the Fe particles, which kept them small and dense. During CVD, CH4 prevented the Fe particles from coarsening, resulting in an enhanced growth lifetime and suppressed diameter increase of growing SWCNTs.

Millimeter-tall single-walled carbon nanotubes rapidly grown with and without water.

Millimeter-tall vertically aligned single-walled carbon nanotubes (SWCNTs) were grown in 10-15 min by chemical vapor deposition from C(2)H(2)/Ar with or without water addition using Fe catalyst supported on an Al-Si-O underlayer. Using combinatorial catalyst libraries coupled with the real-time monitoring of SWCNT growth, the catalyst and chemical vapor deposition conditions were systematically examined, and millimeter-tall SWCNTs were obtained even without water addition. The key for millimeter-scale growth of SWCNTs is to limit the C(2)H(2) supply to below a certain partial pressure to retain an active catalyst.

Efficient field emission from triode-type 1D arrays of carbon nanotubes.

Carbon nanotube (CNT) emitters were formed on line-patterned cathodes in microtrenches through a thermal CVD process. Single-walled carbon nanotubes (SWCNTs) self-organized along the trench lines with a submicron inter-CNT spacing. Excellent field emission (FE) properties were obtained: current densities at the anode (J(a)) of 1 microA cm(-2), 10 mA cm(-2) and 100 mA cm(-2) were recorded at gate voltages (V(g)) of 16, 25 and 36 V, respectively.

Growth window and possible mechanism of millimeter-thick single-walled carbon nanotube forests.

Our group recently reproduced the water-assisted growth method, so-called "SuperGrowth", of millimeter-thick single-walled carbon nanotube (SWNT) forests by using C2H4/H2/H2O/Ar reactant gas and Fe/Al2O3, catalyst. In this current work, a parametric study was carried out on both reaction and catalyst conditions. Results revealed that a thin Fe catalyst layer (about 0.