Suguru Noda

Waseda University | Sōdai · Department of Applied Chemistry

Functionalization of nanocarbon materials with heteroatoms is of paramount interest as doping of carbon with electron withdrawing groups results in change of electrochemical properties of the potential catalyst. Adding fluorine, as the most electronegative element into the doping process next to boron is expected to have significant effect on the d...

An unconventional method of improving the electrocatalytically accessible number of Ni sites (ECAS) in a nickel sulphide catalyst has been developed. The unconventional method assisted enhancement in the ECAS of...

Demonstrating extremely large reduction of cross-plane thermal conductivity of graphite by co-intercalating MnCl 2 and FeCl 3 and identifying the mechanism through its thickness and temperature dependences.

A self-supported NiTeO3 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...

In this study, to show the extent to which the use of any reference electrode (RE) in any pH could affect the electrochemical data, Hg/HgO, 1.0 M KOH (MMO, ERef...

Thin film sweat sensors utilizing ionophores have emerged as a powerful and non-invasive method for monitoring health. These sensors offer remarkable sensitivity, selectivity, and rapid response, making them a promising solution for personalized health tracking. Ionophores, specialized molecules with target-specific binding capabilities, enable acc...

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...

Carbon nanotubes (CNTs) configured as sponge-like paper can be used as lightweight three-dimensional electrodes for high-energy-density lithium-ion batteries without the need for binders or metal foils. Here, we report on the appropriate structural properties of CNTs for application in lithium-ion battery electrodes. Negative and positive electrode...

Accurate determination of electrochemical surface area (ECSA) is not always possible even for simple monometallic catalysts with well-known techniques. An example is Pt and the determination of its ECSA by hydrogen underpotential deposition (HUPD) used to determine the specific activity. Here, we show an important problem in determining the ECSA of...

The significant performance decay in conventional graphite anodes under low‐temperature conditions is attributed to the slow diffusion of alkali metal ions, requiring new strategies to enhance the charge storage kinetics at low temperatures. Here, nitrogen (N)‐doped defective crumpled graphene (NCG) is employed as a promising anode to enable stable...

Tafel analysis is one of the most important ways of screening all energy conversion electrocatalysis as it helps to get information on activity (via exchange current density) and mechanism (via Tafel slope). Inappropriate methods of constructing Tafel plots combined with improper interpretation of Tafel parameters (especially Tafel slopes) is cloud...

Self-supporting, sponge-like paper of carbon nanotubes (CNTs) can be a new platform for high energy/power density batteries. Presently, battery electrodes are built on metallic foils having only two faces and large mass with the aid of polymeric binders and conductive fillers. CNT paper can replace all these components. Furthermore, it captures nan...

Examining water splitting electrocatalysts accurately is just as important as developing new and high-performance materials. The recent evolution of materials science and the ability that mankind achieved in controlling and directing the growth of materials at the nanoscale have led to an exponential burst in the number of catalysts being reported...

The hydrogen evolution reaction (HER) is best catalyzed by metallic Pt with the lowest overpotential, Tafel slope, and highest exchange current density. But its scarcity made us look for abundant alternatives which come at the price of poor activity and stability. Hence, all non-Pt HER electrocatalysts are compared with Pt (often Pt/C). In such cas...

Liquid ammonia is able to release hydrogen via electrolysis with a theoretical voltage of 0.077 V. However, the actual operation voltage is much higher (around 1–2 V) due to the large overpotential of the anodic reaction. We systematically investigated Pt, Ir, Ru, Ni, Co, Fe, Ta, and Ti as the anodic catalyst, and observed a volcano correlation whe...

Cyclic and linear sweep voltammetry techniques substantially misjudge the performance of water splitting electrocatalysts due to their transient nature that forbids the interface from reaching a steady-state. This misjudgment leads to the potentially detrimental yet unwittingly falsified data accumulation in the literature that requires immediate a...

Potentiostatic direct current (DC) voltammetric techniques are in use for decades now in the screening of electrocatalysts used in energy conversion devices, sensors, and electrolyzers despite being inferior in many...

Hydrogen production from water via electrolysis is widely investigated these days with several electrocatalysts in order to make it economically viable. From precious noble metals to highly abundant Fe, each element has its own energy of interaction with the intermediates involved in total water electrosplitting and behaves according to the environ...

We have demonstrated a blackbody micro-emitter using etching-precipitation graphene that requires no transfer process. Long-lifetime and bright emission are achieved by using a bow-tie-shaped graphene. This graphene-based micro-emitter is expected to be applied to integrated photonics and optoelectronics.

Electrocatalytic water splitting activity trend is mainly justified using two activity markers namely the electrochemical surface area measured in terms of double-layer capacitance (Cdl) and the charge transfer resistance (Rct). In general, a better active catalyst always tends to have higher Cdl and lower Rct. The non-Faradaic Cdl has so far been...

The MgH2-Nb2O5-carbon nanotube (CNT) composite was fabricated to accommodate the volume change of particles during the hydrogen storage cycles by holding the MgH2-Nb2O5 particles within the sponge-like matrix of the CNT. This allowed for preservation of the composite structure and led to more stable hydrogen sorption properties during 20 cycles, as...

Human sweat contains a variety of substances, some of which are correlated with sweat in the body. Therefore, measuring the concentration of certain substances in sweat can play an important role in health management. However, it has been suggested that pH affects the measurements in sweat, and it would be beneficial to know the pH in order to impr...

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 th...

Turnover frequency (TOF) serves as an accurate descriptor of the intrinsic activity of a catalyst. However, if it is reported at all, it has not been accurately determined in most of the recent studies on electrocatalytic reactions involving both fuel generation and fuel consumption. This Viewpoint stresses the significance of realistic TOF data in...

Controlling catalyst-particle formation is essential for the growth of single-wall carbon nanotube (SWCNT) arrays with improved alignment, areal mass, and height. We have previously reported the positive effect of CO2 on SWCNT growth via chemical vapor deposition, and in this study, we found its negative effect on catalyst-particle formation during...

Carbon nanotube (CNT)/silicon heterojunction solar cells have been extensively studied owing to the ease of junction fabrication. Encouraging power conversion efficiencies (PCEs) have been reported; however, many of them are limited to small cells (<1 cm²). Herein, we report MoOx as a multifunctional layer that enables the size and performance enha...

We report the controllable pore structures of pure (> 99.5 wt%) and sub-millimeter-long single-walled and few-walled (triple-walled on average) carbon nanotubes (SWCNTs and FWCNTs, respectively) synthesized via fluidized-bed chemical vapor deposition. The pore structures and adsorption properties of the CNTs were characterized using N2 adsorption a...

Needs of a material for thermal management in reduced-sized electronic devices drive single-walled carbon nanotubes (SWCNTs) to be one of the most promising candidates due to their excellent thermal properties. Many numerical and experimental studies have reported on understanding thermal properties of the SWCNT for thermal device applications. In...

To produce carbon nanotubes (CNTs) practically, a high carbon source concentration and high carbon yield are essential. By feeding moderately active ethylene at 10–20 vol% with mildly oxidative carbon dioxide at 1 vol%, submillimeter-long single-wall CNT (SWCNT) arrays were synthesized via fluidized-bed chemical vapor deposition using an Fe/AlOx ca...

Lithium-sulfur battery suffers from the low utilization of sulfur and the high electrolyte/sulfur (E/S) ratio that decrease the cell-based performance. Lithium polysulfides (Li2Sx)-dissolved electrolyte, so called catholyte, enables high utilization of sulfur, but the cell inherently has high E/S ratio due to the limited solubility of Li2Sx. Herein...

We propose using hydrogen as a heat transfer medium to supply waste heat from hydrogen-driven devices to hydrogen storage tanks. In our model, MgH2 is used in the form of porous sheets, set in parallel in the tank, and heat is supplied via hot hydrogen flowed through the interspaces between the porous sheets. Feasibility of the hydrogen desorption...

Electrocatalytic water splitting, a field of recent interest in the hydrogen energy realm, has been growing rapidly with contributions from interdisciplinary researchers of different academic backgrounds in science and engineering. The ability acquired with recent advances in nanostructuring materials led to the development of high-performance cata...

Carbon nanotube/silicon solar cells have increasingly attracted attention owing to their high efficiency and cost-effectiveness. Herein, we demonstrated a significant improvement in the performance of the carbon nanotube/silicon solar cell by applying solution-processable MoOx. The MoOx acts as both an efficient chemical dopant and an anti-reflecti...

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 fo...

Redox‐active organic compounds have attracted substantial attention as charge storage materials due to their high theoretical capacity. Herein, the two‐dimensional organic electrode material is prepared using hydrothermally polymerized dopamine molecules on graphene nanosheets. Two‐dimensional polydopamine is employed as a positive electrode for st...

A carbon nanotube forest with a length of 14 cm grew with an average growth rate of 1.5 μm s⁻¹ and a growth lifetime of 26 h. Several key factors to realize this unprecedented long growth such as catalyst conditions, growth conditions in chemical vapor deposition, and reactor system were clarified. It was found that the combination of the catalyst...

The energy and power performance of lithium (Li)‐ion batteries is significantly reduced at low‐temperature conditions, which is mainly due to the slow diffusion of Li‐ions in graphite anode. Here, it is demonstrated that the effective utilization of the surface‐controlled charge storage mechanism through the transition from layered graphite to 3D c...

Carbon nanotube (CNT)/n-Si heterojunction solar cells were fabricated based on solution processes. CNT film with high transparency of 90% and low sheet resistance of ∼115 Ω/sq was fabricated from commercially available CNT powder via dispersion-filtration process using poly(p-styrene-sulfonic acid) (PSS) as both dispersant and dopant. Heterojunctio...

This review brings out the key advancements made in the field of alkaline HER with metal hydroxides and their heterostructures and also provides a detailed and critical analysis of strategies and perspectives used with highlights on future prospects at the end. Abstract Transition metal hydroxides (M‐OH) and their heterostructures (X|M‐OH, where X...

We recently reported the fastest anodization method (just 80 s) of all for accessing a denser array of Cu(OH)2–CuO nanoneedles on a Cu foil substrate by applying a constant potential of 0.864 V vs a reversible hydrogen electrode in 1.0 M KOH that delivered a better activity for the methanol oxidation reaction (MOR). In this study, we show that the...

Stainless steel 304 (SS-304) foil is an excellent catalytic electrode for the oxygen evolution reaction of water splitting in alkali given that the surface of which is engineered specifically. In this work, the same has been surface engineered for the first time with a two-step approach that made it a high-rate hydrogen evolution. The first step of...

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...

In this study, we show a simple two-step surface engineering method that uses chemical oxidation (using KOH and NaClO in 1:2 M ratio)-assisted leaching of metals (Cr, Mn, and Ni) from the surface and an electrochemical potentiostatic activation enabled resurfacing of only catalytically active Ni and Mn of the alloy. Such surface-engineered stainles...

Electrodeposition of palladium nanoparticles (PdNPs) was investigated on single walled carbon nanotubes (SWCNTs) or few walled carbon nanotubes (FWCNTs) dispersed in 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)amide (BMPTFSA) containing [PdBr 4 ] ² ⁻ . Ionic liquids have been expected to be alternative electrolytes for electrodepositi...

Electrocatalytic oxygen evolution reaction (OER) catalyzed by non-precious metals and their compounds in alkaline medium is an attractive area of energy research for the generation of hydrogen from water. The 3d transition metals, particularly, Ni and Co show better OER activity than others in alkaline medium. Ni and Co based oxygen-evolving cataly...

Oxygen evolution reaction (OER) is the bottleneck for realizing energy-efficient hydrogen production through water electrolysis in both acid and alkali. Alkaline OER electrocatalyzed by Ni and Co hydroxides are well known which showed unexpected enhancement with the addition of Fe. We found that the commercially procured Cu foam containing trace am...

Non-oxide/hydroxide hydrogen evolution reaction (HER) catalysts undergo hydroxylation to a significant extent even under reductive condition when exposed to alkali. Actual role of such hydroxylation in alkaline HER electrocatalysis is not previously given any significance. In this study, we report an intriguing finding that nickel sulfide a well-kn...

We developed a facile mist deposition method that yields nanometer-thick catalyst films on ceramic beads using aqueous solution of metal nitrates as a low cost catalyst precursor through two different strategies: (a) using a monolayer of a mixture of Fe(NO3)3 and Al(NO3)3 (Fe + Al) and (b) using a bilayer of Fe(NO3)3 on top of the mixture of Fe(NO3...

A common battery platform made of inorganic nanotubes is proposed and developed. Sponge-like papers of conductive carbon nanotubes and insulative boron nitride nanotubes are used as current collector and separator, respectively. The electrode/separator stack, enlarging active material content to 93.6% and functioning without any problem after heati...

A swift potentiostatic anodization method for growing 5–7 µm tall nanoneedle array of Cu(OH)2-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-2 at 0.65 V vs. Hg/HgO which is superior to...

Electrochemical impedance spectroscopy (EIS) is an efficient tool that reveals the electrochemical characteristics of catalysts, surfaces, interfaces, coatings, etc. Use of EIS in different areas of energy research wherever current, potential, and charge determine the performance has become inevitable. Electrocatalytic water splitting is one of suc...

Nickel selenide is an important class of nickel chalcogenide that has recently gained greater attention in electrochemical water splitting. Though other chalcogenides such as sulphides and tellurides have also been shown to possess appreciable electrocatalytic water splitting activity as both cathode and anode material, the electrocatalytic activit...

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 superc...

Cobalt chalcogenides are excellent oxygen evolution reaction (OER) pre-catalysts in alkaline medium as they readily form O2 evolving CoOOH entities in electrochemically accessible Co2+ sites when subjected to anodic potential. A key factor that determines the efficiency of OER in cobalt chalcogenides is the number of electrochemically accessible Co...

Electrochemically polymerized anthraquinone derivatives on conductive carbon nanotubes (CNTs) are redox active as organic cathode materials for lithium-ion batteries. Density functional theory calculations and electrochemical measurements reveal that the polymerized anthraquinone cathodes exhibit the multiple redox reactions with electrolyte ions t...

Carbon nanotubes (CNTs) have been integrated into many electronic and energy devices due to their high conductivity and flexibility. Here, we report the discovery of poly (p-styrene-sulfonic acid) (PSS) as an efficient dispersant and stable dopant for CNTs. PSS showed an excellent dispersion performance; CNTs were partially dispersed by just stirri...

Electrolysis of ammonia in an aqueous solution can generate hydrogen gas at room temperature. An anode reaction of nitrogen gas desorption on ammonia electrolysis has a much larger overvoltage than that of a cathode reaction, and one of the useful electrode catalysts for the anode reaction is platinum (Pt). In this study, in order to increase the s...

Electrochemical water splitting powered by electrical energy derived from renewable sources is a green and faster way of producing bulk hydrogen with the highest purity. Unfortunately, the cost-inefficiency associated with energy loss (as overpotential) and costs of electrode materials have been forbidding this technology to surpass the currently d...

For the practical use of innovative, high-energy-density batteries, loading of high-capacity active materials at high gravimetric and volumetric fractions is required. In this work, a flexible self-supporting paper of few-wall carbon nanotubes (FWCNTs) was used as three-dimensional conductive matrices to capture Si and S at ∼70 mass% without metal...

Improvement in chemical vapor deposition (CVD) methods to efficiently synthesize high-quality carbon nanotubes (CNTs) is critical to realize full potential of commercial application of CNTs. Meanwhile methods with less environmental impact from the synthesis process and the use of material and energy are preferable for sustainable chemistry. Howeve...

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. Electrocata...

Multi-millimeter-tall vertically-aligned single-wall carbon nanotube (VA-SWCNT) forests were grown using Fe/Gd/Al2O x catalyst with high initial growth rate of ~2 μm s-1 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. The analysis of the VA-SWCNT for...

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 co...

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. Here, we developed a facile...

Heterojunctions of carbon nanotubes interfaced with silicon and doped with AuCl3 can achieve attractive power conversion efficiencies when operated in the photovoltaic regime; however, the cost and long-term stability of such devices must be improved before they could become commercially viable. Here, we investigate the role of chemical treatment o...

The development of semitransparent photoanodes is required for the construction of tandem photoelectrochemical (PEC) water splitting cells incorporating photocathodes. However, the poor stability of transparent conductive oxides at high temperatures hampers the growth of non‐oxide photoanodes with intense visible light absorption. In this work, sem...

We report a high-productivity chemical vapor deposition (CVD) process of graphene by extending the reaction field to three dimensions (3D) and shortening the CVD time to a few minutes. A large Cu foil (5 × 30 cm ² ) is rolled up and set in a small reactor (3.4 cm in diameter), and a continuous graphene film is obtained uniformly in a short time (1....

Direct formation of graphene films on dielectric substrates is investigated by the “etching-precipitation” method which converts metal-carbon mixed films to graphene films by etching metal away by Cl 2 at 600–650 °C. Here we report a new approach for improved control of the layer number and continuity of the graphene films. Reactive sputtering of F...

To make lithium-sulfur battery competitive with commercialized lithium ion batteries, sulfur cathodes need to be of high sulfur content, thick and dense. We use 35 μm-thick, sponge-like free-standing papers of carbon nanotube (CNT) as three-dimensional conductive matrices, and simply capture sulfur in them by sublimation without using any binder. D...

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 SWCNT...

Liquid-feed flame spray pyrolysis (LF-FSP) of selected metalloorganics provides [NiO]0.25[Al2O3]0.75 and [NiO]0.5[Al2O3]0.5 spinel nanopowders (NPs) without aggregation and with good stoichiometric control. Both compositions were processed to thin films as a first step in preparing Ni:Al2O3 nanocomposite films for catalytic synthesis of CNTs. NPs d...

Self-supporting AC (activated carbon)-FWCNT (few-wall carbon nanotubes) hybrid electrodes were fabricated by mixing of ACs with high specific surface area (SSA) and sub-millimeter-long FWCNTs. In order to fabricate the hybrid electrodes, AC and FWCNT were mixed in a weight ratio of 9:1, dispersed by bath-sonication and vacuum-filtrated on a membran...

The lithium secondary batteries with higher energy density is strongly required for electric vehicle application. The sulfur cathode and silicon anode show high theoretical capacity (1675 mAh g sulfur ⁻¹ and 3580 mAh g silicon ⁻¹ ). Nevertheless, both active materials change their volume during charge-discharge cycles, which leads to pulverization...

Silicon remains the most widely employed material in solar cell due to the low cost, lack of toxicity, and small electronic band gap for near-infrared to visible light absorption. However, up to now, one of the main limitations of silicon solar cells is their high temperature and complex manufacturing processes. Recently, silicon solar cells hybrid...

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 low temperature chemical vapor deposition process (470 °C). The cyclic voltammetry (CV) measurements of K4[Fe(CN)6] showed the redox current of IDE with CNT fo...