Yoshitaka Aoki

Yoshitaka Aoki
Hokkaido University | Hokudai · Faculty of Engineering

About

222
Publications
13,841
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2,740
Citations
Citations since 2017
95 Research Items
1737 Citations
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20172018201920202021202220230100200300400
20172018201920202021202220230100200300400
20172018201920202021202220230100200300400

Publications

Publications (222)
Article
Full-text available
Rechargeable aqueous zinc (Zn)‐ion batteries (RAZIBs), which use non‐flammable aqueous electrolytes and low‐cost electrode materials, show great potential to boost the development of safe, cost‐effective, and highly efficient energy storage systems. The adoption of lightweight and inexpensive aluminum (Al) as current collectors seems to be a good v...
Article
Full-text available
Currently, the development of high‐performance protonic ceramic cells (PCCs) is limited by the scarcity of efficient mixed protonic–electronic conducting oxides that can act as air electrodes to satisfy the high protonic conductivity of electrolytes. Despite the extensive research efforts in the past decades, the development of mixed protonic–elect...
Article
Full-text available
Protonic Ceramic Fuel Cells Protonic ceramic fuel cells (PCFCs) working at an intermediate temperature range have been emerging as a promising clean power generation technology. In article number 2201882, Lei Du, Baoyin Yuan, Siyu Ye and co‐workers present a comprehensive review on advanced cathode materials with tailorable H+, O2−, and e− conducti...
Article
Oxyhydrides have excellent potential as electrochemical and catalytic materials owing to the synergistic effects of the conductivity and redox activity of the hydride (H-) ion. However, harsh preparation conditions and their pyrolytic nature limit their applications. Herein, we discover highly durable oxyhydride perovskite BaZr0.5In(II)0.5O2.25H0.5...
Article
Introduction Rechargeable aqueous zinc-ion batteries (RAZIBs) have some inherent advantages such as intrinsic safety, low-cost and theoretically high energy density, making them a current topic of interest. The problem is, dendritic growth of zinc (Zn) metal during electrodeposition occurs whatever alkaline electrolyte or neutral electrolyte, which...
Article
This study investigates the oxygen evolution reaction (OER) activity of the FeNiCo alloy anodized at several temperatures in a fluoride-containing ethylene glycol electrolyte. When the alloy is anodized at 10 V, the OER activity in KOH electrolyte is highly enhanced on the alloy anodized at 15 and 20°C, at which non-uniform film growth proceeds. Th...
Article
Intermediate‐temperature proton ceramic fuel cells (PCFCs)–a promising power generation technology–have attracted significant attention in recent years because of their unique advantages over conventional high‐temperature solid oxide fuel cells and low‐temperature proton exchange membrane fuel cells. The cathodes of PCFCs simultaneously require eff...
Article
Hydration treatment of aluminum in hot water is important for its corrosion protection, and also this treatment is a crucial pretreatment in forming dielectric crystalline alumina films on the aluminum anode in aluminum electrolytic capacitors. In this study, a two-layer hydrated film formed on high purity aluminum by hot water treatment was examin...
Article
Full-text available
Proton-conducting solid oxide electrolysis cells (H-SOEC) containing a 15-μm-thick BaZr0.6Ce0.2Y0.2O3-δ (BZCY622) electrolyte thin film, porous cathode cermet support, and La0.6Sr0.4Co0.2Fe0.8O3-δ anodes were fabricated using a reactive cofiring process at approximately 1400 °C. Steam electrolysis was conducted by supplying wet air to the anode at...
Article
Hydrogen, especially the “green hydrogen” based on water electrolysis, is of great importance to build a sustainable society due to its high-energy-density, zero-carbon-emission features, and wide-range applications. Today’s water electrolysis is usually carried out in either low-temperature (<100 °C), e.g., alkaline electrolyzer, or high-temperatu...
Article
Rechargeable aqueous zinc (Zn) batteries have attracted great interests because of its inherent safety and cost-effectiveness. However, the uncontrollable Zn dendrite formation in aqueous electrolyte restricts its reversibility for long-life application. The bulge or passivation layer in pristine Zn surface serves as nuclei for large amount of Zn c...
Article
Rechargeable aqueous zinc-ion batteries (RAZIBs) have some inherent advantages such as intrinsic safety, low-cost and theoretically high energy density, making them a current topic of interest. However, the phenomenon of...
Article
This study revealed excellent corrosion resistance of the highly graphitized platelet-type carbon nanofibers due to hydroxyl passivation of the carbon edge plane.
Article
Protonic solid oxide electrolysis cells (P-SOECs) are one of the most efficient devices for hydrogen production from renewable electricity, but a lack of suitable anodes has led to serious concerns...
Article
Among several types of low‐temperature solid oxide fuel cells, hydrogen‐permeable metal‐supported fuel cells (HMFCs) are devices that can achieve outputs of approximately 1.0 W cm−2 at 400 °C. This work clarifies the mechanism for promoting the cathode reaction on proton‐conducting ceramics at such low temperatures. Combined numerical and electroch...
Article
Because of the limited availability of fossil fuels and pertinent global environmental issues, hydrogen production via electrochemical water splitting using renewable resources is an important alternative for future energy economies. For efficient alkaline water electrolysis to produce hydrogen, we need to develop highly active and durable electroc...
Article
Protonic solid oxide steam electrolysis cells (P-SOECs) based on BaZrxCe0.8xYb0.1Y0.1O3−δ proton conductors are promising to produce “green” hydrogen from renewable energy at intermediate temperatures. Herein, we demonstrate that the electrolysis performances of a cell with a high-Zr-content electrolyte, BaZr0.6Ce0.2Y0.1Yb0.1O3−δ (BZCYYb6211), can...
Article
The reaction pathway of the oxygen reduction reaction (ORR) is strongly affected by the electrolytic environment. Meanwhile, the ORR mechanism on transition-metal oxide catalysts has not been studied intensely in very concentrated alkaline solutions that are used in practical metal-air batteries. Herein, we report the in situ activation of ORR cata...
Article
Full-text available
Graphene-covering is a promising approach for achieving an acid-stable, non-noble-metal-catalysed hydrogen evolution reaction (HER). Optimization of the number of graphene-covering layers and the density of defects generated by chemical doping is crucial for achieving a balance between corrosion resistance and catalytic activity. Here, we investiga...
Article
On the way to achieve practical lithium (Li) metal anode for next-generation batteries, the formation and accumulation of inactive “Dead Li” is an unavoidable issue. The accumulation of “Dead Li”...
Article
A simple anodizing technique has been employed to develop highly active electrocatalysts that can be applied to the oxygen evolution reaction (OER) in alkaline media. NiFe alloys were electrodeposited and anodized to form a porous electrocatalytic layer. This approach produces highly active electrodes without the need for noble metals, binders, or...
Article
1. Introduction Lithium (Li) metal is regarded as the ideal anode for lithium batteries due to its ultra-high theoretical specific capacity (3860 mAh g ⁻¹ ), low density (0.59 g cm ⁻³ ) and lowest negative electrochemical potential (-3.04 V vs. Standard Hydrogen Electrode). ⁽¹⁾ However, caused by several remaining hurdles, including i) the thermody...
Article
Zinc-air secondary battery (ZAB) is a promising candidate for the development of new generation of energy conversion systems due to its relatively high theoretical energy density of 1370 Wh kg ⁻¹ . The decrease of overpotential for oxygen-reduction-reaction (ORR) and oxygen-evolution-reaction (OER) in air electrode, together with providing of high...
Article
A solid oxide steam electrolysis cell (SOEC) has attracted much attention for the production of a clean H 2 from water by using renewable electricity. Activation energy of proton conduction in proton conducting perovskite oxides BaZr x Ce 1- x-y Y y O 3-δ (BZCY) is much lower than that of yttria stabilized zirconia which is practically used for the...
Article
Protonic ceramic cells (PCCs), including fuel cells and electrolysis cells, are based on protonic conducting Ba(Zr, Ce)O 3 electrolytes, and have more advantages at operating temperatures below 600 °C than solid oxide cells (SOCs) based on a oxide ion conducting Y-ZrO 2 because the activation energy required for proton conduction (0.3–0.6 eV) is lo...
Article
Hydration treatment of aluminum is often used for corrosion protection of aluminum alloys and for the formation of dielectric alumina layer in aluminum electrolytic capacitors. Hydrated alumina layer is usually formed by immersing aluminum with and without a porous anodic alumina layer in hot water. The hydrated alumina layer plays an important rol...
Article
Protonic ceramic fuel cells (PCFCs) have been drawing considerable attentions because of their potential for high-power operating at intermediate temperature (IT), 400–600°C, which is a salient issue for their practical implementation. BaZr 0.1 Ce 0.7 Y 0.2 O 3 , popular proton-conducting ceramic electrolyte material, has notably high conductivity...
Article
Full-text available
In this study, zinc is anodized at different voltages in 0.1 mol·dm−3 KOH electrolyte to form nanoporous anodic films. Dark-colored anodic films are formed at anodizing voltages ≤ 6 V, whereas colorless anodic films are developed at voltages ≥ 7 V. The anodic films formed at all voltages consist of crystalline ZnO, which was identified by X-ray dif...
Article
Anodizing of iron (100), (110) and (111) single crystals in mono-ethylene-glycol electrolyte containing 1.5 mol dm−3 water and 0.1 mol dm−3 ammonium fluoride leads to formation of anodic iron nanopores/nanotubes where the nanopores are essentially composed of oxide nanotubes separated by iron fluoride matrix. It was found that electrochemical therm...
Article
Full-text available
Development of highly active bifunctional electrocatalysts for oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) is required for air electrodes of zinc-air secondary batteries (ZAB). In this study, we synthesize spinel-type MnCo2O4 (MCO) nanoparticles on highly graphitized platelet-type carbon nanofibers (pCNF) via a solvothermal...
Article
Full-text available
The effect of alloying sputter-deposited Ti with 2 at.% of Au on the growth of anodic nanotubes was studied in monoethylene glycol electrolyte containing 1.0 mol dm−3 of water and 0.1 mol dm−3 of ammonium fluoride. The classic shape of nanotubes modified with quasi-spherical clusters of Au48-198 was obtained on Ti-Au (2 at.%). The results were comp...
Article
Copper is an important practical metal with a high thermal conductivity that is widely used as a heat exchanger material. However, a liquid film often forms on the Cu surface through water vapor condensation, causing a large resistance to heat transfer. To address this issue, a superhydrophobic Cu metal nanowire surface is developed herein via Cu a...
Article
Slippery Surfaces In article number 1900836 by Tomohiro Inoue, Hiroki Habazaki and co‐workers, fluorine‐free slippery liquid‐infused porous surface (SLIPS) is prepared using hierarchically porous aluminum substrate and silicone lubricant. The F‐free SLIPS is more environmentally acceptable compared with the F‐containing SLIPS and exhibits highly re...
Article
Brownmillerite-type Ca2FeCoO5 (CFCO) is a highly active electrocatalyst for the oxygen evolution reaction (OER). In this study, we identified the actual catalytically active phase of this oxide formed via the long-term OER and, moreover, demonstrated that the active phase can persist during the OER for four weeks without significant loss of electro...
Article
Full-text available
It is challenging for materials chemists to develop efficient, cobalt-free cathode materials for solid oxide fuel cells mainly because of the resource scarcity. This study demonstrates that a cubic-type La0.7Sr0.3Mn0.7Ni0.3O3-δ (C-LSMN7373) perovskite is promising for intermediate-temperature protonic ceramic fuel cells (PCFCs) because of the suffi...
Article
Hindered by dendrite growth, unceasing volume change and repeated regeneration of solid-state electrolyte interface, the practical application of lithium (Li) metal anode is still facing challenges from low Coulombic efficiency (CE), insufficient safety performance and poor cyclic stability. Current collector plays a key role in regulating Li depos...
Article
Porous anodic alumina films formed by anodizing of aluminum in acid electrolytes have a highly ordered, nanopore channels, which have attracted increased attention as template for various nanomaterials. Utilizing this template, platelet-type carbon nanofibers (pCNFs) have been successfully prepared by simply heating a mixture of the template and po...
Article
Anodizing is a high voltage electrochemical conversion process that forms barrier-type oxide layers or self-organized nanoporous/nanotubular structures. So far, alumina-like nanopores and titania-like nanotubes could be successfully synthesized on many valve metals and alloys. Recently, anodizing become possible for base metals such as polycrystall...
Article
Highly durable air electrodes for the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) in highly alkaline media are necessary to catalyze reactions in metal-air secondary batteries. Carbon is able to provide electronic conductivity and co-catalyze reactions, however, is typically oxidized under high-potential conditions above 1.1...
Article
Organic phase change materials (PCM, such as paraffin) are broadly used in thermal energy storage systems, especially for the efficient utilization of solar energy and industrial waste heat, whereas their low shape-stability and poor heat transfer performance have hindered the practical applications. In this work, we aim at producing high-performan...
Article
Slippery liquid infused porous surfaces (SLIPS) have been receiving increased attention. Fluorinated compounds have been used to prepare the SLIPS, but because of bioaccumulation and ecological impact of perfluoalkyl building blocks, fluorine‐free SLIPS system is preferable for practical applications. In this study, SLIPS has been prepared from hie...
Article
Protonic ceramic fuel cells (PCFCs) have limited application below 500○C owing to their high ohmic and polarization resistances. Hence, efforts are ongoing to develop advanced fuel cells based on semiconductor device science as well as material interfacial engineering. Here, we demonstrate that hydrogen-permeable metal-supported fuel cells (HMFCs)...
Article
The utilization of a Li metal anode is necessary in the development of next generation high energy density Li batteries, which is still hindered by problems of dendrite growth, volume change and electrolyte depletion. To overcome these difficulties, the employment of 3D porous current collectors has been demonstrated to be an effective strategy. Ho...
Article
The formation of crystalline anatase films having important applications such as photocatalysis, solar cells, electrochromic applications, and bio-implants requires time-consuming multiple processes including heat treatments. In this paper, ultra-rapid formation of a crystalline anatase film on a tin substrate is realized by a cathodic deposition m...
Article
Full-text available
Mixed proton-electron conductors (MPECs) are indispensable for the efficient operation of proton conducting ceramic fuel cells and electrolyzer cells at intermediate temperatures (below 500 ○C), but robust guidelines for their material design are still missing. Here, this study firstly reports on the massive uptake of proton carriers in cubic perov...
Article
Anodizing of metals and alloys is a simple electrochemical process to form various nano-structured oxide films, including self-ordered nanoporous and nanotubular films. Typical examples are nanoporous alumina films with honeycomb morphology and nanotubular array of anodic titanium oxide. Recently, several nanowire-type anodic films have been prepar...
Preprint
Full-text available
Recharchable zinc-air-battery is considered as one of the possible candidates to replace conventional lithium ion battery. One of the requirements for effective battery operation is an oxygen evolution reaction (OER) which needs to be provided in highly alkaline electrolyte. The A2BB`O5 Brownmillerite-type Ca2FeCoO5 electrocatalyst having 57 Pbcm s...
Article
Full-text available
Recharchable zinc-air-battery is considered as one of the possible candidates to replace conventional lithium ion battery. One of the requirements for effective battery operation is an oxygen evolution reaction (OER) which needs to be provided in highly alkaline electrolyte. The A2BB`O5 Brownmillerite-type Ca2FeCoO5 electrocatalyst having 57 Pbcm s...
Article
Herein, high-valence-state Mn(V) oxide, barium manganate(V) (Ba3(MnO4)2), was examined as an anode electrocatalyst of a H⁺-conducting solid oxide steam electrolysis cell (H-SOEC). Ba3(MnO4)2 comprises C3v-symmetric MnO4³⁻ oxo-anions with three Mn-O single bonds and one Mn=O double bond because a lone pair of Mn⁵⁺ cation in d² configuration tends to...
Article
Biomass-derived porous carbons with very high specific surface area (SSA) and heteroatom-doping are important for obtaining high performance supercapacitor. In this study, we report a simple and straightforward strategy, which involves the efficient and exothermic pyrolysis of Mg/K/Mg·K-nitrate-urea-cellulose mixture with subsequent high temperatur...
Article
Full-text available
The effect of alloying of sputter-deposited Fe with 9 at.% tungsten on the growth of nanoporous anodic oxide was studied in ethylene glycol electrolyte containing 0.1 mol dm-3 ammonium fluoride and 1.5 mol dm-3 water. The classic nanoporous anodic film (Al2O3-like) was developed on pure Fe while the transition of nanopores to nanotubes (TiO2-like)...
Article
In this work, high value-added N-doped hierarchical porous carbon (NHPC) for oxygen reduction reaction (ORR) electrocatalyst was prepared using biomass cellulose as the raw material. The pyrolysis of cellulose is accelerated by a redox combustion reaction of magnesium nitrate-carbohydrates (urea and cellulose) as-absorbed in cellulose fibers, which...
Article
Full-text available
In this study, platelet-type carbon nanofibers prepared by the liquid phase carbonization of polymers in the pores of a porous anodic alumina template were used to prepare the Co3O4/carbon electrocatalysts. For comparison, Co3O4 nanoparticles were also deposited on multiwall carbon nanotubes (MWCNTs). Both the nitrogen-free platelet-type carbon nan...
Article
Stainless steels is practically important corrosion-resistant metallic materials, and additional surface functionalities including self-cleaning, anti-fouling, anti-ice and snow sticking and fluid drag reduction by the introduction of superhydrophobic and superoleophobic surfaces are of recent interest. Here, we report the micro-/nano-hierarchical...
Article
Electrocatalytic activity for the 4e- transfer oxygen reduction reaction (ORR) was examined with perovskite-type La0.7Sr0.3Mn1-xNixO3-δ (x = 0-0.5) compounds in concentrated KOH. Electrochemical measurements by means of a rotating ring-disc electrode technique revealed that 10% substitution of Mn by Ni atoms significantly improved ORR activity wher...
Article
Anodizing is a high voltage electrochemical conversion process that forms barrier-type oxide layers or self-organized nanoporous/nanotubular structures. So far, the Al 2 O 3 -like nanopores and TiO 2 -like nanotubes could be successfully synthesized on many valve metals and alloys. The proposed models of anodic oxide nanotubes growth, however, sacr...
Article
Full-text available
This paper reports a survey of power generation characteristics of anode-supported thin film fuel cells with Zr-rich BaZrxCe0.8−xY0.2O3−δ (x = 0.4, 0.6, 0.7, and 0.8) proton-conducting electrolytes, which were fabricated by single step co-firing with Zn(NO3)2 additives at a relatively low temperature (1400 °C). The grain sizes significantly increas...
Article
Full-text available
The growth of a uniform barrier-type anodic film on aluminum is usually terminated by electric breakdown, which is controlled by the resistance of electrolyte or anion concentration. In this study, highly resistive porous layers have been introduced by anodizing aluminum in sulfuric acid electrolyte followed by boiling water treatment to examine th...
Article
This paper reports rapid self‐healing on superoleophobic hierarchically porous aluminum surfaces within 1 h even at room temperature. This self‐healing surface is prepared by infiltration of a liquid fluoroalkylsilane (FAS) coating into the substrate pores. The FAS‐infiltrated dual‐pore superoleophobic surface becomes superoleophilic after oxygen p...
Article
This paper reports unusual diffusion-controlled growth of TiO2 mesoporous anodic films on titanium in hot phosphate/glycerol electrolytes. The formation behavior was investigated by cyclic voltammetry (CV) between 0 and 5 V vs. Pt at 433 K. The current density became almost constant above 1.5 V vs. Pt during the positive potential sweep, and was ma...
Article
Porous carbon has attracted great interest because of its distinctive structure and superior properties for designing electrochemical energy storage devices. In this work, we report a novel and facile method to fabricate nitrogen-doped porous carbon (NPC) with designed hierarchical multi-porous structure. The NPC is prepared using a facile and scal...
Article
The development of green and clean synthetic techniques to produce carbon materials for energy storage and conversion applications has motivated researchers to use sustainable biomass. In this study, hierarchical porous carbon (HPC) with very high specific surface area and controlled porosity is synthesized by a novel and facile method, which emplo...
Article
Metal oxides with high dielectric constant are extensively studied in the frame of substituting SiO2 as gate dielectric in nanoelectronic devices. Here, high‐k mixed HfO2/Nb2O5 oxides are prepared by a facile electrochemical route starting from sputtering‐deposited Hf–Nb alloys with several compositions. Transmission electron microscopy, grazing in...
Article
The oxygen reduction reaction (ORR) catalytic activity was systematically studied on the BaLnMn2O5 series (Ln = Y, Gd, Nd and La) with a layered double-perovskite-type structure in an alkaline aqueous solution. The onset ORR potential and the number of electrons involved in ORR were found to be strongly Ln-dependent: both values were obviously high...
Article
Full-text available
The Front Cover illustrates the transition of anodic nanopores into nanotubes during the anodizing process. The compositional fingerprints of this transition obtained by high-resolution TEM/EDS imaging shed light onto the general mechanism of nanotube growth in organic electrolytes containing fluorides. More information can be found in the Article...
Article
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The front cover artwork is provided by the Laboratory of Interfacial Electrochemistry, Hokkaido University (Japan). The image illustrates the transition of anodic nanopores into nanotubes during the anodizing process. The compositional fingerprints of this transition, acquired by using high‐resolution TEM/EDS, shed light on the general mechanism of...
Article
Hydrogen permeability based on mixed hydridic ion electron conduction was demonstrated for hafnium nitrides HfNx (film thickness of 100–500 nm, x = 0.8 and 1.0) nanocrystalline membranes. Nanocrystalline films with (100) orientation and crystallite sizes of a few tens of nanometers were prepared on porous alumina supports by radio frequency (rf) re...
Article
Anodic reaction pathways in proton-conducting solid oxide electrolyzer cells (H⁺−SOECs) were investigated using electrochemical impedance spectroscopy with a cell structure of Sm0.5Sr0.5CoO3 (anode) | BaZr0.4Ce0.4Y0.2O3-δ | Pt (cathode). Densely sintered BaZr0.4Ce0.4Y0.2O3-δ ceramics (>97% relative density) were fabricated by a reactive sintering p...
Article
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A direct ammonia-type intermediate temperature fuel cell is examined by means of a hydrogen membrane fuel cell (HMFC) comprising 1-µm-thick BaZr0.1Ce0.7Y0.2O3- δ (BZCY) thin-film electrolyte and Pd solid anode. It generates the maximum power density of 0.58 W cm-2 at 600 °C with ammonia fuels, and this value is found to be three times larger than t...