Author
Jiahui Zhu
Bio: Jiahui Zhu is an academic researcher from Soochow University (Suzhou). The author has contributed to research in topics: Mesoporous material & Overpotential. The author has an hindex of 4, co-authored 6 publications receiving 86 citations.
Topics: Mesoporous material, Overpotential, Nanowire, Radical, Catalysis
Papers
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TL;DR: Novel ordered mesoporous core-shell nanowires with Mo2C cores and ultrathin graphitic carbon (GC) shells are rationally synthesized and demonstrated to be excellent for HER.
Abstract: Mo2C is a possible substitute to Pt-group metals for electrocatalytic hydrogen evolution reaction (HER). Both support-free and carbon-supported Mo2C nanomaterials with improved HER performance have been developed. Herein, distinct from prior research, novel ordered mesoporous core-shell nanowires with Mo2C cores and ultrathin graphitic carbon (GC) shells are rationally synthesized and demonstrated to be excellent for HER. The synthesis is fulfilled via a hard-templating approach combining in situ carburization and localized carbon deposition. Phosphomolybdic acid confined in the SBA-15 template is first converted to MoO2, which is then in situ carburized to Mo2C nanowires with abundant surface defects. Simultaneously, GC layer (the thickness is down to ∼1.0 nm in most areas) is controlled to be locally deposited on the Mo2C surface because of its strong affinity with carbon and catalytic effect on graphitization. Removal of the template results in the Mo2C@GC core-shell nanowire arrays with the structural properties well-characterized. They exhibit excellent performance for HER with a low overpotential of 125 mV at 10 mA cm-2, a small Tafel slope of 66 mV dec-1, and an excellent stability in acidic electrolytes. The influences of several factors, especially the spatial configuration and relative contents of the GC and Mo2C components, on HER performance are elucidated with control experiments. The excellent HER performance of the mesoporous Mo2C@GC core-shell nanowire arrays originates from the rough Mo2C nanowires with diverse active sites and short charge-transfer paths and the ultrathin GC shells with improved surface area, electronic conductivity, and stabilizing effect on Mo2C.
42 citations
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TL;DR: In this article, a 3D ordered macroporous framework built from ultrathin micro/mesoporous nitrogen-doped graphene-like walls is proposed to enrich accessible active sites and shorten the mass and electron transport paths.
Abstract: Hierarchical carbon materials are highly attractive for energy storage and conversion. To improve their performances in electrocatalytic oxygen reduction and supercapacitors, the construction of 3D ordered macroporous frameworks built from ultrathin micro/mesoporous nitrogen-doped graphene-like walls is proposed to enrich accessible active sites and shorten the mass and electron transport paths. A surface-coating hard-templating method is developed for this purpose. The synthesis involves packing silica nanospheres into an opal, designed surface coating with histidine, carbonizing and template removal. The strong adhesive binding between silica and histidine and cohesive interactions among histidine molecules direct the uniform coating and subsequent formation of ultrathin (∼2.8 nm) carbon layers. Various N-doped inverse opal carbons (N-IOCs) with ordered macropores, graphene-like walls, high surface areas up to ∼1365 m2 g−1, narrow micro/mesopores of 0.6–5.0 nm, and high N content up to ∼14.72 wt% are obtained. The optimized N-IOCs exhibit outstanding performances in the oxygen reduction reaction with extraordinary activities, up to 0.95 and 0.87 V for the onset and half-wave potentials, which are among the best for heteroatom-doped carbon materials reported thus far, and excellent methanol tolerance and stability, as well as showing high capacitances of up to 222 F g−1 and good rate capability and stability in supercapacitors. Control experiments reveal that the remarkable performance is ascribed to the ordered macropores for rapid mass transportation, the ultrathin carbon layers for fast electron transfer, and the high surface areas for hosting abundant active sites.
29 citations
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TL;DR: In this paper, a simple solvent free reactive nanocasting approach that integrates solid precursor loading, in-situ sulfuration and carbonization into a single heating step is developed for the universal synthesis of ordered mesoporous TMS@N-doped carbon composites.
Abstract: Transition metal sulfides (TMSs) have a wide range of applications owing to their intriguing properties. Significant efforts have been devoted to nanostructuring TMSs to enhance their properties and performance, still there is a high need in general synthesis of TMS nanostructures. Herein, for the first time, a simple solvent free reactive nanocasting approach that integrates solid precursor loading, in-situ sulfuration and carbonization into a single heating step is developed for the universal synthesis of ordered mesoporous TMS@N-doped carbon composites (denoted as OM-TMS@NCs) with methionine (Met) and metal chlorides as the precursors and the mesoporous silica (SBA-15) as the hard template. A series of OM-TMS@NCs with a hexagonal mesostructure, ultra-high surface areas (430–754 m2·g−1), large pore volumes (0.85–1.32 cm3·g−1), and unique TMS stoichiometries, including MoS2, Fe7S8, Co9S8, NiS, Cu7S4 and ZnS, are obtained. Two distinct structure configurations, namely, highly dispersed ultrathin TMS nanosheets within NCs and TMS@NC co-nanowire arrays, can be obtained depending on different metals. The structure evolution of the OM-TMS@NCs over the solvent-free nanocasting process is studied in detail for a deep understanding of the synthesis. As demonstrations, these materials are promising for electrocatalytic hydrogen evolution reaction and lithium ion storage with high performances.
25 citations
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03 May 2019TL;DR: The facile and general synthesis of alkaline-earth metal manganites, denoted as A(Mg, Ca, Ba)MnxOy, for efficient degradation of high-concentration phenolic compounds via catalytic ozonation is demonstrated, exhibiting rapid pseudofirst-order degradation kinetics, a high total organic carbon removal efficiency and an excellent stability.
Abstract: In this paper, we demonstrate the facile and general synthesis of alkaline-earth metal manganites, denoted as A(Mg, Ca, Ba)MnxOy, for efficient degradation of high-concentration phenolic compounds via catalytic ozonation. The representative CaMnxOy oxides show a hierarchical spherical structure constructed by crystalline nanorods and numerous macropores. They possess mixed Mn4+/Mn3+ chemical valences and abundant surface hydroxyl (OH) groups. The ozone (O3) decomposition rate on the CaMnxOy catalysts is greatly accelerated and follows the first-order law. These catalysts are promising for the degradation of phenolic compounds via catalytic ozonation, exhibiting rapid pseudofirst-order degradation kinetics, a high total organic carbon (TOC) removal efficiency and an excellent stability. Under optimized conditions (a low O3 dosage of 1.5 mg/min and a catalyst dosage of 7.5 g/L), for the treatment of concentrated phenol (50–240 mg/L), the CaMnxOy catalysts show 100% degradation and 50–70% mineralization within 1.0 h. The Ca2+ ions are essential to create redox Mn4+/Mn3+ couples and to significantly reduce manganese leaching. High surface ratios of Mn4+/Mn3+ and OH/lattice oxygen (Olat) are beneficial for enhancing the catalytic performance. Superoxide anion free radicals ( O2–) and singlet oxygen (1O2) are the predominant reactive species for the oxidation degradation. The O2– reaction pathway is proposed. Specifically, the surface OH sites activate O3, displaying highly enhanced decomposition rates. The generated O2– and 1O2 play a role in oxidation. The redox Mn4+/Mn3+ and the Olat/oxygen vacancy (Olat/Ovac) couples play important roles in electron transfer. The proposed mechanism is supported by active site probing, radical scavenging, spectroscopic studies, and the results in the degradation of substituted phenols.
23 citations
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TL;DR: In this paper, an acid-base molecular assembly strategy is demonstrated for the synthesis of novel N-doped Mo2C@C core-shell nanowires (NWs) composed of mesoporous Mo 2C cores with interconnected crystalline walls and ultrathin carbon shells.
13 citations
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253 citations
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TL;DR: Carbon-based materials have multiple advantages including abundant sources, tunable molecular structures, high electronic conductivity, and environmental compatibility as mentioned in this paper. But, there is no systematic review yet covering all the general methods to boost carbon-based electrocatalysts for ORR/OER/HER, and reporting their most recent progress.
181 citations
01 Sep 2016
TL;DR: Using novel porous (holey) metallic 1T phase MoS2 nanosheets synthesized by a liquid-ammonia-assisted lithiation route, this study systematically investigated the contributions of crystal structure, edges, and sulfur vacancies to the catalytic activity toward HER and revealed that the phase serves as the key role in determining the HER performance.
Abstract: Molybdenum disulfide (MoS2) is a promising nonprecious catalyst for the hydrogen evolution reaction (HER) that has been extensively studied due to its excellent performance, but the lack of understanding of the factors that impact its catalytic activity hinders further design and enhancement of MoS2-based electrocatalysts. Here, by using novel porous (holey) metallic 1T phase MoS2 nanosheets synthesized by a liquid-ammonia-assisted lithiation route, we systematically investigated the contributions of crystal structure (phase), edges, and sulfur vacancies (S-vacancies) to the catalytic activity toward HER from five representative MoS2 nanosheet samples, including 2H and 1T phase, porous 2H and 1T phase, and sulfur-compensated porous 2H phase. Superior HER catalytic activity was achieved in the porous 1T phase MoS2 nanosheets that have even more edges and S-vacancies than conventional 1T phase MoS2. A comparative study revealed that the phase serves as the key role in determining the HER performance, as 1T phase MoS2 always outperforms the corresponding 2H phase MoS2 samples, and that both edges and S-vacancies also contribute significantly to the catalytic activity in porous MoS2 samples. Then, using combined defect characterization techniques of electron spin resonance spectroscopy and positron annihilation lifetime spectroscopy to quantify the S-vacancies, the contributions of each factor were individually elucidated. This study presents new insights and opens up new avenues for designing electrocatalysts based on MoS2 or other layered materials with enhanced HER performance.
175 citations
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TL;DR: Heterostructured Mo 2 C-MoO x on carbon cloth, as a model of easily oxidized electrocatalysts under ambient conditions, is investigated to uncover surface reconfiguration during hydrogen evolution reaction (HER), and consistent in-situ surface reconfigured and promotion are proved.
Abstract: Heterostructured Mo2 C-MoOx on carbon cloth (Mo2 C-MoOx /CC), as a model of easily oxidized electrocatalysts under ambient conditions, is investigated to uncover surface reconfiguration during the hydrogen evolution reaction (HER). Raman spectroscopy combined with electrochemical tests demonstrates that the MoVI oxides on the surface are in situ reduced to MoIV , accomplishing promoted HER in acidic condition. As indicated by density functional theoretical calculations, the in situ reduced surface with terminal Mo=O moieties can effectively bring the negative ΔGH* on bare Mo2 C close to a thermodynamic neutral value, addressing difficult H* desorption toward fast HER kinetics. The optimized Mo2 C-MoOx /CC only requires a low overpotential (η10 ) of 60 mV at -10 mA cm-2 in 1.0 m HClO4 , outperforming Mo2 C/CC and most non-precious electrocatalysts. In situ surface reconfiguration are shown on W2 C-WOx , highlighting the significance to boost various metal-carbides and to identify active sites.
136 citations
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03 Apr 2019TL;DR: A review of carbon-encapsulated materials for the hydrogen evolution reaction (HER) is presented in this paper, with a focus on the unique effects of carbon shells, and perspectives on the future development of carboncoated electrocatalysts for the HER are provided.
Abstract: Water electrolysis is a promising approach for large-scale and sustainable hydrogen production; however, its kinetics is slow and requires precious metal electrocatalysts to efficiently operate. Therefore, great efforts are being undertaken to design and prepare low-cost and highly efficient electrocatalysts to boost the hydrogen evolution reaction (HER). This is because traditional transition-metal electrocatalysts and corresponding hybrids with nonmetal atoms rely mainly on the interaction of metal–H bonds for the HER, which inevitably suffers from corrosion in extreme acidic and alkaline solutions. And as a result of all this effort, novel nanostructured electrocatalysts, such as carbon-encapsulated precious metals and non-precious metals including single metals or their alloys, transition-metal carbides, phosphides, oxides, sulfides, and selenides have all been recently reported to exhibit good catalytic activities and stabilities for hydrogen evolution. Here, the catalytic activity is thought to originate from the electron penetration effect of the inner metals to the surface carbon, which can alter the Gibbs free energy of hydrogen adsorption on the surface of materials. In this review, recent progresses of carbon-encapsulated materials for the HER are summarized, with a focus on the unique effects of carbon shells. In addition, perspectives on the future development of carbon-coated electrocatalysts for the HER are provided. Carbon-encapsulated electrocatalysts, such as carbon-encapsulated precious metals and non-precious metals (single metals or their alloys, metal carbides, phosphides, oxides, sulfides, and selenides), are emerging as promising candidates for water splitting. In this review, recent progresses in carbon-encapsulated electrocatalysts for hydrogen evolution are reviewed, especially the unique effects of carbon shells.
128 citations