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2019, Vol. 36, No. 9　Online: 2019-09-15

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Bismuth doped lead-free two-dimensional tin based halide perovskite single crystals Ruiling Zhang, Xin Mao, Pengfei Cheng, Yang Yang, Songqiu Yang, Tuerdi Wumaier, Weiqiao Deng, Keli Han 2019, 36(9): 1-6.  DOI: 10.1016/j.jechem.2018.12.003 摘要 ( 54 )   Heterovalent-metal doping is an efficient tool to tune the optoelectronic properties of the famous halide perovskites. Previous studies have focused on the heterovalent-doping in three-dimensional (3D) halide perovskites. However, there is a lack of such doping in two-dimensional perovskites which possess unique optoelectronic properties and improved chemical stability as compared to 3D analogues. Here, we present successful doping of Bismuth into the lattice of lead-free, two-dimensional perovskite PEA2SnBr4 single crystals. Structural characterizations demonstrate that the doped crystals possess identical crystal structure and layered morphology with the pristine one. Intriguingly, we find the PL peak and spectral shape can be tailored by tuning the concentration of Bi dopants. Femtosecond transient absorption spectroscopy is performed to understand the underlying mechanism related to tunable PL behaviors, and a clear picture of the Bismuth-doping impact is provided.

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Regression model for stabilization energies associated with anion ordering in perovskite-type oxynitrides Masanori Kaneko, Mikiya Fujii, Takashi Hisatomi, Koichi Yamashita, Kazunari Domen 2019, 36(9): 7-14.  DOI: 10.1016/j.jechem.2019.01.012 摘要 ( 14 )   Certain perovskite-type oxynitrides have bandgaps suitable for renewable hydrogen production via photocatalytic and photoelectrochemical water splitting under visible light. Understanding the ordering of oxide and nitride anions in these materials is important because this ordering affects their semiconductor properties. However, the numerous possible orderings complicate systematic analyses based on density functional theory (DFT) calculations using defined elemental arrangements. This work shows that anion ordering in large-scale supercells within perovskite-type oxynitrides can be rapidly predicted based on machine learning, using BaNbO2N (capable of oxidizing water under irradiation up to 740 nm) as an example. Machine learning allows the calculation of the total energy of BaNbO2N directly from randomly selected initial atomic placements without costly structural optimization, thus reducing the computational cost by more than 99.99%. Combined with the Metropolis Monte Carlo method, machine learning permits exploration of the stable anion orderings of large supercells without costly DFT calculations. This work therefore demonstrates a means of predicting the properties of functional materials having complex compositions based on the most realistic elemental arrangements in conjunction with reasonable computational loads.

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The hydrogenation of levulinic acid to γ-valerolactone over Cu-ZrO2 catalysts prepared by a pH-gradient methodology Igor Orlowski, Mark Douthwaite, Sarwat Iqbal, James S. Hayward, Thomas E. Davies, Jonathan K. Bartley, Peter J. Miedziak, Jun Hirayama, David J. Morgan, David J. Willock, Graham J. Hutchings 2019, 36(9): 15-24.  DOI: 10.1016/j.jechem.2019.01.015 摘要 ( 12 )   A novel pH gradient methodology was used to synthesise a series of Cu-ZrO2 catalysts containing different quantities of Cu and Zr. All of the catalysts were highly selective to the desired product, γ-valerolactone, and are considerably more stable than Cu-ZrO2 catalysts prepared by other co-precipitation methods for this reaction. Characterisation and further investigation of these catalysts by XRD, BET, SEM and XPS provided insight into the nature of the catalytic active site and the physicochemical properties that lead to catalyst stability. We consider the active site to be the interface between Cu/CuOx and ZrOx and that lattice Cu species assist with the dispersion of surface Cu through the promotion of a strong metal support interaction. This enhanced understanding of the active site and roles of lattice and surface Cu will assist with future catalyst design. As such, we conclude that the activity of Cu-ZrO2 catalysts in this reaction is dictated by the quantity of Cu-Zr interface sites.

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Recent progress towards mild-condition ammonia synthesis Qianru Wang, Jianping Guo, Ping Chen 2019, 36(9): 25-36.  DOI: 10.1016/j.jechem.2019.01.027 摘要 ( 79 )   Ammonia is essential for food and energy. Industrial ammonia synthesis via Haber-Bosch process is energy-intensive and releases large amount of CO2. Increasing research efforts are devoted to "green" ammonia synthesis. The present article reviews the recent progress in the fields of thermocatalytic, electrocatalytic, photocatalytic and chemical looping processes for dinitrogen reduction towards ammonia formation and discusses the challenges borne for mild-condition synthesis.

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Photocatalytic one-step synthesis of Ag nanoparticles without reducing agent and their catalytic redox performance supported on carbon Lingling Shui, Guoxiu Zhang, Bin Hu, Xingxing Chen, Mingliang Jin, Guofu Zhou, Nan Li, Martin Muhler, Baoxiang Peng 2019, 36(9): 37-46.  DOI: 10.1016/j.jechem.2019.04.006 摘要 ( 14 )   Synthesis of silver nanoparticles (Ag NPs) with state-of-the-art chemical or photo-reduction methods generally takes several steps and requires both reducing agents and stabilizers to obtain NPs with narrow size distribution. Herein, we report a novel method to synthesize Ag NPs rapidly in one step, achieving typical particle sizes in the range from 5 to 15 nm. The synthesis steps only involve three chemicals without any reducing agent:AgNO3 as precursor, polyvinylpyrrolidone (PVP) as stabilizer, and AgCl as photocatalyst. The Ag NPs were supported on carbon and showed excellent performance in thermal catalytic p-nitrophenol reduction and nitrobenzene hydrogenation, and as electrocatalyst for the oxygen reduction reaction.

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Room-temperature conversion of ethane and the mechanism understanding over single iron atoms confined in graphene Suheng Wang, Haobo Li, Mengqi He, Xiaoju Cui, Lei Hua, Haiyang Li, Jianping Xiao, Liang Yu, N. Pethan Rajan, Zhaoxiong Xie, Dehui Deng 2019, 36(9): 47-50.  DOI: 10.1016/j.jechem.2019.04.003 摘要 ( 12 )   The catalytic conversion of ethane to high value-added chemicals is significantly important for utilization of hydrocarbon resources. However, it is a great challenge due to the typically required high temperature (> 400℃) conditions. Herein, a highly active catalytic conversion process of ethane at room temperature (25℃) is reported on single iron atoms confined in graphene via the porphyrin-like N4-coordination structures. Combining with the operando time of flight mass spectrometer and density functional theory calculations, the reaction is identified as a radical mechanism, in which the C-H bonds of the same C atom are preferentially and sequentially activated, generating the value-added C2 chemicals, simultaneously avoiding the over-oxidation of the products to CO2. The in-situ formed O-FeN4-O structure at the single iron atom serves as the active center for the reaction and facilitates the formation of ethyl radicals. This work deepens the understanding of alkane C-H activation on the FeN4 center and provides the reference in development of efficient catalyst for selective oxidation of light alkane.

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Dimethyl ether carbonylation over zeolites Ensheng Zhan, Zhiping Xiong, Wenjie Shen 2019, 36(9): 51-63.  DOI: 10.1016/j.jechem.2019.04.015 摘要 ( 31 )   Syngas to ethanol, consisting of dimethyl ether (DME) carbonylation to methyl acetate (MA) over zeolites and MA hydrogenation to ethanol on copper catalyst, has been developed in recent years. DME carbonylation over zeolites, a key step in this new process, has attracted increasing attention due to the high reaction efficiency and promising industrial application. In recent years, continuous efforts have been made on improving the activity and stability of the zeolites. From a mechanistic point of view, DME carbonylation to MA, involving the formation of C-C bond, is achieved via the Koch-type CO insertion into DME within the 8-member ring (8-MR) pores of zeolites, typically HMOR and HZSM-35. The unique geometric configuration of the 8-MR pore endowed the formation of the key intermediate (acetyl, CH3CO*), possibly by a spatial confinement of the transition state during CO insertion into the surface O-CH3 group. This review article summarizes the main progress on zeolite-catalyzed DME carbonylation, including reaction kinetics and mechanism, theoretical calculations, and experimental strategies developed for populating acid sites and engineering pore structure of the zeolites in order to enhance the overall performance.

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2D hierarchical yolk-shell heterostructures as advanced host-interlayer integrated electrode for enhanced Li-S batteries Yanfeng Dong, Pengfei Lu, Haodong Shi, Jieqiong Qin, Jian Chen, Wencai Ren, Hui-Ming Cheng, Zhong-Shuai Wu 2019, 36(9): 64-73.  DOI: 10.1016/j.jechem.2019.04.023 摘要 ( 7 )   Lithium sulfur (Li-S) batteries hold great promising for high-energy-density batteries, but appear rapid capacity fading due to the lack of overall and elaborated design of both sulfur host and interlayer. Herein, we developed a novel two-dimensional (2D) hierarchical yolk-shell heterostructure, constructed by a graphene yolk, 2D void and outer shell of vertically aligned carbon-mediated MoS2 nanosheets (G@void@MoS2/C), as advanced host-interlayer integrated electrode for Li-S batteries. Notably, the 2D void, with a typical thickness of~80 nm, provided suitable space for loading and confining nano sulfur, and vertically aligned ultrathin MoS2 nanosheets guaranteed enriched catalytically active sites to effectively promote the transition of soluble polysulfides. The conductive graphene yolk and carbon mediated shell sufficiently accelerated electron transport. Therefore, the integrated electrode of G@void@MoS2/C not only exceptionally confined the sulfur/polysulfides in 2D yolk-shell heterostructures, but also achieved catalytic transition of the residual polysulfides dissolved in electrolyte to solid Li2S2/Li2S, both of which synergistically achieved an extremely low capacity fading rate of 0.05% per cycle over 1000 times at 2 C, outperforming most reported Mo based cathodes and interlayers for Li-S batteries. 2D hierarchical yolkshell heterostructures developed here may shed new insight on elaborated design of integrated electrodes for Li-S batteries.

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Advances in catalytic conversion of lignocellulose to chemicals and liquid fuels Jiping Ma, Song Shi, Xiuquan Jia, Fei Xia, Hong Ma, Jin Gao, Jie Xu 2019, 36(9): 74-86.  DOI: 10.1016/j.jechem.2019.04.026 摘要 ( 35 )   In response to the awareness of limited fossil resources and environmental concerns, catalytic conversion of renewable lignocellulose biomass to value-added chemicals and fuels is of great significance and attractive for sustainable chemistry. Division of Biomass Conversion and Bio-Energy attached to Dalian National Laboratory for Clean Energy has devoted themselves to valorization of lignocellulose biomass since launched in 2011. Our research interests focus on breeding of biomass resources (inulin and microalgae), exploration of catalytic and biological technologies, and production of energy chemicals and fuels. Although lignocellulose biomass is renewable and abundant, the way of utilization should be reasonable according to its structural characteristics in view of efficiency and economy. In this review, to celebrate the DICP's 70th anniversary, we will highlight the major fundamental advances in DICP about the conversion of lignocellulose to value-added chemicals and liquid fuels. Particular attention will be paid to the transformation of cellulose and its derivatives to glycols, acids and nitrogen-containing chemicals, hemicellulose-derived platform molecule furfural to jet fuels and lignin to aromatics using catalytic technologies.

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Detrimental phase evolution triggered by Ni in perovskite-type cathodes for CO2 electroreduction Shiqing Hu, Lixiao Zhang, Huanying Liu, Wenping Li, Zhongwei Cao, Lili Cai, Yue Zhu, Xuefeng Zhu, Weishen Yang 2019, 36(9): 87-94.  DOI: 10.1016/j.jechem.2019.06.001 摘要 ( 2 )   Perovskite oxides are popular as cathode materials of solid oxide electrolysis cells, because of their good redox stability and high resistance to coke formation. Unexpectedly, a negative effect of Ni doping is found on Sr2Fe1.5-xNixMo0.5O (x=0, 0.05, 0.1, 0.2) cathode for pure CO2 electroreduction at 800℃, although Ni is highly active for CO2 electroreduction. The CO2 electroreduction performance degrades with the increase of Ni doping amount. Various characterization techniques are used to disclose the negative effect. Ni doping decreases the perovskite stability under electroreduction conditions, Fe and Ni cations in the B-site are reduced to metal nanoparticles and SrCO3 forms on the surface of the perovskite. The phase instability results from the weaker Ni-O bond. Although the Fe-Ni nanoparticles are in favor of the CO2 electroreduction, too much SrCO3 and carbon deposition block the charge transfer and diffusion of oxygenous species on the cathode surface.

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Rational design of carbon-based metal-free catalysts for electrochemical carbon dioxide reduction: A review Song Liu, Hongbin Yang, Xiong Su, Jie Ding, Qing Mao, Yanqiang Huang, Tao Zhang, Bin Liu 2019, 36(9): 95-105.  DOI: 10.1016/j.jechem.2019.06.013 摘要 ( 17 )   Electrochemical CO2 reduction to chemicals or fuels presents one of the most promising strategies for managing the global carbon balance, which yet poses a significant challenge due to lack of efficient and durable electrocatalyst as well as the understanding of the CO2 reduction reaction (CO2RR) mechanism. Benefiting from the large surface area, high electrical conductivity, and tunable structure, carbon-based metal-free materials (CMs) have been extensively studied as cost-effective electrocatalysts for CO2RR. The development of CMs with low cost, high activity and durability for CO2RR has been considered as one of the most active and competitive directions in electrochemistry and material science. In this review article, some up-to-date strategies in improving the CO2RR performance on CMs are summarized. Specifically, the approaches to optimize the adsorption of CO2RR intermediates, such as tuning the physical and electronic structure are introduced, which can enhance the electrocatalytic activity of CMs effectively. Finally, some design strategies are proposed to prepare CMs with high activity and selectivity for CO2RR.

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Pseudohalide induced tunable electronic and excitonic properties in two-dimensional single-layer perovskite for photovoltaics and photoelectronic applications Zhuo Xu, Ming Chen, Shengzhong (Frank) Liu 2019, 36(9): 106-113.  DOI: 10.1016/j.jechem.2019.07.004 摘要 ( 14 )   Two-dimensional (2D) layered organic-inorganic hybrid perovskites have attracted much more attention for some applications than their three-dimensional (3D) perovskite counterparts due to their promising thermal and moisture stabilities. In particular, the 2D perovskite devices have shown better promise for optoelectronic applications. However, tunability of optoelectronic properties is often demanded to improve the device performance. Herein, we adopt a newly method to tune the electronic properties of 2D perovskite by introducing pseudohalide into the structure. In this work, we designed a pseudohalidesubstituted 2D perovskite by substituting the out-of-plane halide with pseudohalide and studied the electronic and excitonic properties of 2D-BA2MX4 and 2D-BA2MX2Ps2 (M=Ge2+, Sn2+, and Pb2+; X=I; Ps=NCO, NCS, OCN, SCN, SeCN). We revealed the dependence of electronic properties including band gaps, composition of band edges, bonding characteristics, work functions, effective masses, and exciton binding energies on different pseudohalides substituted in 2D perovskite. Our results indicate that the substitution of pseudohalide in 2D perovskites is energetically favorable and can significantly affect the bonding characteristics as well as the CBM and VBM that often play major role in determining their performance in optoelectronic devices. It is expected that the pseudohalide substitution will be helpful in developing more advanced optoelectronic device based on 2D perovskite by optimizing band alignment and promoting charge extraction.

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Etherification of HMF to biodiesel additives: The role of NH4+ confinement in Beta zeolites Paola Lanzafame, Georgia Papanikolaou, Katia Barbera, Gabriele Centi, Siglinda Perathoner 2019, 36(9): 114-121.  DOI: 10.1016/j.jechem.2019.07.009 摘要 ( 10 )   The role of NH4+ ion confinement in the catalytic etherification of HMF (5-hydroxymethylfurfural) with ethanol to biodiesel additives was evidenced by studying the catalytic behavior of NH4+-Beta zeolites with SiO2/Al2O3 ratios of 25 and 75. In order to affect the strength and distribution of the acidic sites, as well as the mobility of NH4+ ions in the zeolites cages, a secondary level of porosity was introduced in the NH4+-Beta, presenting a different stability versus alkaline treatment, by using a thermal or an ultrasound assisted method. By analyzing the catalytic behavior in these two series of samples with respect to the changes in porosity by nonlocal density functional theory, structure by XRD, amount of acid sites by FT-IR and mobility of NH4+ cations by measurements of reversible NH4+ exchange capacity, was evidenced a decrease in catalytic performances both in terms of rate of HMF depletion and productivity to the main products, when confinement of the ammonium ions is lost due to the introduction of mesoporosity. The high capability of ammonium ions release, associated to the mono-dentate configuration, and the minor confinement effect inside the zeolite pore system, due to the more opened pores structure of mesoporous zeolites, hinders both the direct etherification of HMF to EMF[5-(ethoxymethyl) furan-2-carbaldehyde] and the parallel reaction pathway via acetalization, favoring the rapid desorption of the HMFDEA[5-(hydroxymethyl) furfural diethyl acetal] product out of the crystal and the consequent inhibition of the consecutive reactions to EMFDEA[5-(ethoxymethyl) furfural diethyl acetal] and EMF.

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Highly selective adsorption of CO over N2 on CuCl-loaded SAPO-34 adsorbent Yaqi Wu, Zhaoan Chen, Bing Li, Jiacheng Xing, Hanbang Liu, Yansi Tong, Peng Tian, Yunpeng Xu, Zhongmin Liu 2019, 36(9): 122-128.  DOI: 10.1016/j.jechem.2019.07.013 摘要 ( 5 )   Carbon monoxide (CO)/N2 separation is of importance for current chemical industry. However, CO/N2 separation remains a challenge due to the similar molecular size and the small variance of volatility of CO and N2. In this work, molecular sieve SAPO-34 was loaded with CuCl by monolayer dispersion method for the preparation of Cu(I) containing adsorbents. The resulted adsorbents were characterized via nitrogen adsorption/desorption at 77 K, X-ray fluorescence (XRF) and X-ray diffraction (XRD). The results indicated that CuCl was successful loaded into the molecular sieve and well-dispersed. CO and N2 single component adsorption isotherms were recorded under 298 K, 308 K and 318 K by using volumetric method. One of the CuCl-loaded SAPO-34 adsorbent exhibited a very high CO adsorption capacity of 1.84 mmol/g at 100 kPa, 298 K and high CO/N2 selectivity.

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Recent progresses in H2-PEMFC at DICP Feng Xie, Zhigang Shao, Ming Hou, Hongmei Yu, Wei Song, Shucheng Sun, Li Zhou, Baolian Yi 2019, 36(9): 129-140.  DOI: 10.1016/j.jechem.2019.07.012 摘要 ( 13 )   Proton exchange membrane fuel cell (PEMFC) as a power supply device has attracted wide attention in China and abroad for its advantages of high energy density, energy conversion efficiency and zero pollution. With the vigorous support of China's national policy, research institutes and enterprises have carried out extensive and pragmatic work on the basic materials, key components, stacks, auxiliary systems of PEMFCs, as well as the hydrogen station construction in order to realize the wide application of hydrogen energy. PEMFC System and Engineering Research Center of DICP is one of the earliest players in the H2-PEMFCs field. Advances have been achieved in the fields of low-platinum contained catalysts, PEMs, high-efficiency MEAs, low-cost metal bipolar plates, low-temperature and impurity air environment adaptability, stacks and systems. This paper introduces recent progresses of H2-PEMFCs at DICP in key materials, components, stacks, systems and the applications. The engineering status of proton exchange membrane water electrolysis (PEMWE) and the alkaline anion exchange membrane fuel cells (AEMFCs) are also summarized.

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Selective conversion of syngas to propane over ZnCrOx-SSZ-39 OX-ZEO catalysts Gen Li, Feng Jiao, Dengyun Miao, Yong Wang, Xiulian Pan, Toshiyuki Yokoi, Xiangju Meng, Feng-Shou Xiao, Andrei-Nicolae Parvulescu, Ulrich Müller, Xinhe Bao 2019, 36(9): 141-147.  DOI: 10.1016/j.jechem.2019.07.006 摘要 ( 23 )   Oxide-Zeolite (OX-ZEO) bifunctional catalyst design concept has been exemplified in several processes to direct conversion syngas to value-added chemicals and fuels such as mixed light olefins, ethylene, aromatics and gasoline. Herein we demonstrate that the product can be steered toward liquefied petroleum gas (LPG) with a selectivity up to 89% in hydrocarbons especially propane selectivity reaching 80% at CO conversion of 63% using ZnCrOx-H-SSZ-39 catalyst. Interestingly, the quantity of the acid sites of SSZ-39 does not influence obviously the hydrocarbon distribution but the strength is crucial for selective formation of propane. This finding provides an alternative route of LPG synthesis from a variety of carbon resources via syngas.