ORCID Profile
0000-0002-7577-1366
Current Organisation
Tohoku University
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Materials engineering | Electrochemistry | Functional materials
Publisher: Wiley
Date: 12-2020
Publisher: AIP Publishing
Date: 22-03-2023
DOI: 10.1063/5.0147123
Abstract: Due to conversion equilibrium between solvent and H- and O-containing adsorbates, the true surface state of a catalyst under a particular electrochemical condition is often overlooked in electrocatalysis research. Herein, by using surface Pourbaix analysis, we show that many electrocatalytically active transition metal X-ides (e.g., oxides, nitrides, carbides, and hydroxides) tend to possess the surface states different from their pristine stoichiometric forms under the pH and potential of interest due to water dissociation or generation. Summarizing the density functional theory calculated surface Pourbaix diagrams of 14 conditionally stable transition metal X-ide materials, we found that some of these surfaces tend to be covered by O-containing adsorbates at a moderate or high potential, while vacancies or H-covered surfaces may form at a low potential. These results suggest the possibility of poisoning or creation of surface sites beyond the pristine surface, implying that the surface state under reaction conditions (pH and potentials) needs to be considered before the identification and analysis of active sites of a transition metal X-ide catalyst. In addition, we provide an explanation of the observed theory and experiment discrepancy that some transition metal X-ides are “more stable in experiment than in theory.” Based on our findings, we conclude that analyzing the surface state of transition metal X-ide electrocatalysts by theoretical calculations (e.g., surface Pourbaix diagram analysis), in situ/operando and post-reaction experiments are indispensable to accurately understand the underlying catalytic mechanisms.
Publisher: Wiley
Date: 08-03-2022
Abstract: Aqueous supercapacitors show advantages of high safely, prolonged lifespan, and low cost, etc. but there have never been commercial market products, nor quantitative investigation of practical pouch devices of aqueous supercapacitors. Herein, to achieve their lab‐scale to real‐life manufacture, a unique MoO x for supercapacitor use is constructed by a hydrothermal and annealing strategy suitable for industrialization, which plays three key functions, including precisely adjusted interlayer spacing, conductive flexible graphite carbon and abundant oxygen vacancies. As a result, the as‐synthesized electrode yields an ultra‐high specific capacitance of 717 F g −1 at 1 A g −1 and ultra‐long cycling durability with no obvious capacitive loss even after 100 000 cycles. Realistically, the assembled asymmetric supercapacitor (MoO x ‐HDA‐3//MnO 2 ) exhibits extraordinary energy density of 78.2 Wh kg −1 , superior to many advanced supercapacitors reported to date. We have fabricated pouch devices, which can successfully run 3C products such as tablets and smartphones, and maintain stable electrochemical performance even after heavy strikes, fires, and pressures. Quantitative investigation results confirm that the pouch device delivers an excellent specific capacitance of 74.7 F g −1 and a high energy density of 41.5 Wh kg −1 . This work enhances the confidence of pushing aqueous supercapacitors to realistic energy storage market.
Publisher: Wiley
Date: 02-10-2020
Publisher: Wiley
Date: 08-02-2019
Abstract: Due to its electronic structure, similar to platinum, molybdenum carbides (Mo 2 C) hold great promise as a cost‐effective catalyst platform. However, the realization of high‐performance Mo 2 C catalysts is still limited because controlling their particle size and catalytic activity is challenging with current synthesis methods. Here, the synthesis of ultrafine β‐Mo 2 C nanoparticles with narrow size distribution (2.5 ± 0.7 nm) and high mass loading (up to 27.5 wt%) on graphene substrate using a giant Mo‐based polyoxomolybdate cluster, Mo 132 ((NH 4 ) 42 [Mo 132 O 372 (CH 3 COO) 30 (H 2 O) 72 ]·10CH 3 COONH 4 ·300H 2 O) is demonstrated. Moreover, a nitrogen‐containing polymeric binder (polyethyleneimine) is used to create MoN bonds between Mo 2 C nanoparticles and nitrogen‐doped graphene layers, which significantly enhance the catalytic activity of Mo 2 C for the hydrogen evolution reaction, as is revealed by X‐ray photoelectron spectroscopy and density functional theory calculations. The optimal Mo 2 C catalyst shows a large exchange current density of 1.19 mA cm −2 , a high turnover frequency of 0.70 s −1 as well as excellent durability. The demonstrated new strategy opens up the possibility of developing practical platinum substitutes based on Mo 2 C for various catalytic applications.
Publisher: Royal Society of Chemistry (RSC)
Date: 2023
DOI: 10.1039/D2CP05959B
Abstract: Based on first-principles calculations, we designed a highly effective SiM@C 3 N 4 catalyst as the low-cost candidate for electrocatalytic ammonia synthesis.
Publisher: Wiley
Date: 25-05-2023
Abstract: Gold‐based electrocatalysts are potential candidates for electrocatalytic nitrogen reduction reaction (e‐NRR) application due to their high conductivity and low hydrogen evolution tendency. However, the role of nonmetallic Au surfaces is not widely studied. Herein, the self‐assembly of gold nanoparticles confined in carbon felts (Au NPs@CFs) containing two different states of Au is reported, showing effective e‐NRR performance. The effects of surfactant concentration on the morphology and electrochemical performance of the Au NPs are analyzed. X‐ray photoelectron spectroscopy indicates two valence states of Au (Au 0 and Au 3+ ) in Au NPs@CFs. Interestingly, it is found that the e‐NRR properties of Au NPs@CFs enhance with the increase of Au 3+ content. A typical s le Au NPs@CF‐1.0 with the highest Au 3+ content exhibits the best e‐NRR performance (NH 3 yield of 66.1 μg h −1 mg −1 cat. and Faradaic efficiency of 24.9% at −0.3 V vs reversible hydrogen electrode), which, in part due to the presence of Au 3+ , is conducive to nitrogen adsorption. Theoretical calculation results find that a stable Au 3+ surface can adsorb N 2 strongly, which in turn can lead to energetically favorable formation of ammonia. This study provides new insights into the relation between oxidation states and performance of gold‐based electrocatalyst with high e‐NRR performance.
Publisher: Royal Society of Chemistry (RSC)
Date: 2022
DOI: 10.1039/D2TA06458H
Abstract: A “burst effect” was found in the dehydrogenation process of MgH 2 .
Publisher: American Chemical Society (ACS)
Date: 17-12-2020
DOI: 10.1021/JACS.0C10636
Publisher: Wiley
Date: 12-11-2019
Publisher: American Chemical Society (ACS)
Date: 20-12-2020
Publisher: Wiley
Date: 10-03-2021
Publisher: Royal Society of Chemistry (RSC)
Date: 2023
DOI: 10.1039/D3TA04714H
Publisher: Springer Science and Business Media LLC
Date: 06-01-2023
DOI: 10.1038/S42004-022-00810-4
Abstract: Experimentally well-characterized dual-atom catalysts (DACs), where two adjacent metal atoms are stably anchored on carbon defects, have shown some clear advantages in electrocatalysis compared to conventional catalysts and emerging single-atom catalysts. However, most previous theoretical studies directly used a pristine dual-atom site to analyze the electrocatalytic activity of a DAC. Herein, by analyzing 8 homonuclear and 64 heteronuclear DACs structures with ab initio calculations, our derived surface Pourbaix diagrams show that the surface states of DACs generally differ from a pristine surface at electrocatalytic operating conditions. This phenomenon suggests that the surface state of a DAC should be considered before analyzing the catalytic activity in electrocatalysis, while the electrochemistry-driven pre-adsorbed molecules generated from the liquid phase may either change the electronic properties or even block the active site of DACs. Based on these results, we provide a critical comment to the catalyst community: before analyzing the electrocatalytic activity of a DAC, its surface state should be analyzed beforehand.
Publisher: American Chemical Society (ACS)
Date: 25-01-2021
Publisher: Elsevier BV
Date: 10-2023
Publisher: Royal Society of Chemistry (RSC)
Date: 2021
DOI: 10.1039/D0TA10823E
Abstract: Guided by density functional theory calculations, we successfully synthesized a new Ru single-atom catalyst supported on moderately oxidized Cu with outstanding electrocatalytic performance for ammonia synthesis.
Publisher: Wiley
Date: 25-05-2022
Abstract: 2D covalent organic frameworks (COFs) are considered as one kind of the most promising crystalline porous materials for solar‐driven hydrogen production. However, adding noble metal co‐catalysts into the COFs‐based photocatalytic system is always indispensable. Herein, through a simple solvothermal synthesis method, TpPa‐1‐COF, a typical 2D COF, which displays a wide light absorption region, is rationally combined with transition metal phosphides (TMPs) to fabricate three TMPs/TpPa‐1‐COF hybrid materials, named Ni 12 P 5 (Ni 2 P or CoP)/TpPa‐1‐COF. The incorporated TMPs can be served as electron collectors for accelerating the transfer of charges on TpPa‐1‐COF, thus the composites are demonstrated to be efficient photocatalysts for promoting water splitting. Benefitting from the richer surface reactive sites and lower H* formation energy barrier, the Ni 12 P 5 can most effectively improve the photocatalytic performance of the TpPa‐1‐COF, and the H 2 evolution rate can reach up to 31.6 µmol h −1 , approximately 19 times greater than pristine TpPa‐1‐COF (1.65 µmol h −1 ), and is comparable to the Pt/TpPa‐1‐COF (38.8 µmol h −1 ). This work is the first ex le of combining COFs with TMPs to construct efficient photocatalysts, which may offer new insight for constructing noble‐metal‐free COF‐based photocatalysts.
Publisher: Elsevier BV
Date: 06-2022
Publisher: Wiley
Date: 31-01-2021
Publisher: Royal Society of Chemistry (RSC)
Date: 2023
DOI: 10.1039/D2EE02734H
Abstract: Heterogeneous molecular catalysts built from β-substituted cobalt porphyrins and carbon nanotubes afford tunable activity for H 2 O 2 synthesis via the two-electron transfer oxygen reduction reaction.
Publisher: Royal Society of Chemistry (RSC)
Date: 2020
DOI: 10.1039/D0TA04088F
Abstract: Accurate composition–oxygen evolution reaction performance atlases have been established for a ternary Co–Fe–V oxide system using Prussian blue analogues as precursors, affording Co : Fe : V = 3 : 4 : 3 as the optimal metal ratio.
Publisher: Royal Society of Chemistry (RSC)
Date: 2020
DOI: 10.1039/D0TA03237A
Abstract: A facile and efficient strategy to produce nitrogen-doped (N-doped) phosphorene nanosheets that can be used as an efficient metal-free catalyst for electrochemical ammonia synthesis under ambient conditions is presented.
Publisher: Elsevier BV
Date: 04-2021
Publisher: Wiley
Date: 13-08-2023
Abstract: The aqueous Zn ion battery (ZIB) is a potentially sustainable energy storage device. However, its performance is still far from satisfactory. Herein, it is demonstrated that a branched sugar, dextran, widely used in eyedrop products to relieve irritated eyes, is a multifunctional and universal electrolyte additive to enable high‐performance ZIBs. Experimental and theoretical results reveal that dextran has four functions: forming a surface protective layer to minimize side reactions, facilitating stepwise [Zn(H 2 O) 6 ] 2+ desolvation, preferably adsorbing on Zn(0002) planes to supply desolvated Zn 2+ and homogenizing electric field. These functions are universally observed in Zn(CF 3 SO 3 ) 2 , ZnSO 4 , Zn(ClO 4 ) 2 , and ZnCl 2 aqueous electrolytes. As demonstrations for practical applications, Zn anodes deliver Coulombic efficiency of 99.97% after 3400 cycles in an electrolyte with 50 mg mL ‒1 of dextran and cumulative plating capacity of 3400 mAh cm ‒2 at 5 mA cm ‒2 . Zn//V 2 O 5 full cells with a low negative ositive electrode capacity ratio of 2.18 can be stably cycled over 138 cycles at 1 A g ‒1 . Pouch full cells can work under mechanical bending conditions. Zn/ olyaniline full cells can cycle steadily for 3000 cycles at 0.5 A g ‒1 at −10 °C. Dextran shows excellent potential as a low‐cost and non‐toxic electrolyte additive to enable safe and reliable ZIBs.
Publisher: Wiley
Date: 30-06-2023
Abstract: Electrocatalytic nitrogen reduction reaction ( e NRR) relies on developing efficient catalysts towards high reaction activity and selectivity. In recent years, designing single‐atom catalysts have been the research frontier in electrochemical reactions. However, compared to their widely studied applications in oxygen electrocatalysis, their potential structure‐function relationship and reaction mechanism in e NRR were less explored. Herein, single‐atom Fe−N x −C materials were systematically analysed considering the coordination environments of single‐atom Fe. It was found that coordination environment plays a key role in determining the N 2 adsorption and activation. Among the concept catalysts designed, FeCN 2 and FeCN 3 offer the highest e NRR activities with a suppressed side reaction ( i. e ., the hydrogen evolution). Moreover, the Bader charge of the single‐atom Fe and *NH adsorption energy can be the good descriptors to guide the design of e NRR catalysts. This study unravels the key role of coordination environment in tuning the reactivity of e NRR over single‐atom Fe−N x −C materials.
Publisher: Springer Science and Business Media LLC
Date: 02-05-2022
DOI: 10.1038/S41467-022-30034-Y
Abstract: The need for efficient ammonia synthesis is as urgent as ever. Over the past two decades, many attempts to find new catalysts for ammonia synthesis at mild conditions have been reported and, in particular, many new promoters of the catalytic rate have been introduced beyond the traditional K and Cs oxides. Herein, we provide an overview of recent experimental results for non-traditional promoters and develop a comprehensive model to explain how they work. The model has two components. First, we establish what is the most likely structure of the active sites in the presence of the different promoters. We then show that there are two effects dictating the catalytic activity. One is an electrostatic interaction between the adsorbed promoter and the N-N dissociation transition state. In addition, we identify a new promoter effect for magnetic catalysts giving rise to an anomalously large lowering of the activation energy opening the possibility of finding new ammonia synthesis catalysts.
Start Date: 02-2023
End Date: 01-2026
Amount: $565,000.00
Funder: Australian Research Council
View Funded Activity