JUSTC

Structural self-reconstruction and synchrotron radiation characterization of oxygen evolution reaction electrocatalysts

LIU Chongjing, SHENG Beibei, CAO Dengfeng, CHEN Shuangming, SONG Li

2021, 51(11): 787-801. doi: 10.52396/JUST-2021-0193

Abstract:
Self-reconstruction during oxygen evolution reaction (OER) process is considered to be the key to highly active catalysts, while tracking the dynamic changes of catalysts during OER process and identifying the true active sites are challenging. Synchrotron radiation characterizations can obtain the local atomic coordination environment and electron information of specific elements in materials. In particular, in-situ characterization methods can monitor the dynamic evolution of surface oxidation state and local atomic structure transformation under working conditions, which can promote the fundamental understanding of the reaction mechanism. In this review, we discuss recent advances and propose some perspectives in self-reconstruction of OER electrocatalysts, which mainly summarizes the fundamental origin of self-reconstruction behavior and the application of in-situ synchrotron radiation characterization technology to track the dynamic process of self-reconstruction process and to identify the true active sites. Finally, we put forward some challenges and prospects for the development and promotion of self-reconstruction of OER electrocatalysts, hoping to provide guidance for the rational design of advanced OER electrocatalysts.

Sequence-dependent hybridizability of DNA-monoconjugated nanoparticles: Kinetic complexity unveiled by a dimerization assay

WANG Jiannan, ZHENG Yuanqin, LI Yulin, DENG Zhaoxiang

2021, 51(11): 802-812. doi: 10.52396/JUST-2021-0195

Article Views:308 Full article PDF

Abstract:
Understanding DNA hybridization kinetics is highly important for nucleic acid detections, genomic biotechniques, and DNA nanotechnology. DNA-conjugated nanomaterials offer versatile functionalities for DNA-programmable nanoassembly with superfine controls toward bioanalytical and nanotechnological applications. Although small molecule end-tagging does not incur much attenuation of DNA’s hybridizability, nanoparticle-conjugation greatly suppresses the hybridization kinetics of DNA strands. The impeded hybridization not only decreases the efficiency in building complicated nanostructures, but also causes difficulty in realizing rapidly responsive sensors and nanomotors. With monovalent DNA-nanoparticle conjugates as an ideal system, this work aims to unveil the kinetic complexity of hybridization-driven dimeric assembly assayed by agarose gel electrophoresis. Our results point out a coexistence of different factors that can affect the hybridization kinetics of DNA-conjugated nanoparticles, including: the rigidity of a DNA spacer proximal to the nanoparticle surface; the base-stacking between the spacer and a hybridized domain; the inherent base-sequence-dependent DNA hybridizability; and the spatially confined movement of the hybridization sequences. The dimeric hybridization assay offers a reliable platform for kinetic evaluation of DNA-conjugated nanoparticles to enable structurally complicated and rapidly functioning analytical devices and bio-labelling nanoprobes.

Source apportionment of heavy metals in soil of Guangzhou: Comparison of three receptor models

YIN Xiulian, XIE Zhiyi, WANG Wanping, LUO Xiaoling, SHEN Liran, LIU Bianxia, SHAO Limin

2021, 51(11): 813-821. doi: 10.52396/JUST-2021-0169

Article Views:227 Full article PDF

Abstract:
Receptor models are useful tools to identify the types of pollution source and estimate the contributions of each source of the observed samples. To analyze the concentrations, distributions and sources of eight heavy metals including lead (Pb), cadmium (Cd), zinc (Zn), mercury (Hg), arsenic (As), copper (Cu), chromium (Cr), and nickel (Ni) in soils, 208 topsoil samples were collected in the main urban area of Guangzhou, China. Three receptor models (Multi-Linear Regression of the Absolute Principal Component Scores (APCS-MLR) method, Positive Matrix Factorization (PMF) method and UNMIX method) were employed to identify the potential pollution sources of heavy metals and to apportion the pollution sources. Results show that the mean concentrations of eight heavy metal elements are higher than the corresponding background values, with the mean concentration of Cd being almost five times its background value. The three receptor models all identify three potential pollution sources, which are nature source, traffic source and industry source. Moreover, PMF and UNMIX can identify an agricultural source besides the three pollution sources, which better distinguishes the different types of pollution sources. Comparison among the results of APCS-MLR, PMF and UNMIX shows that there are some significant differences in the estimated contributions for each potential pollution source. It is also found that PMF appears to be more plausible for this investigation. It is advisable to use multiple receptor models to perform source identification and source apportionment, and the results could be very useful to local administrations for the control and management of pollution and better protection of important soil quality.

Tuning main-group s-block metal Mg as a promising single-atom electrocatalyst for N₂ fixation: A DFT study

YANG Kang, WANG Changlai, DENG Xi, CHEN Qianwang

2021, 51(11): 822-830. doi: 10.52396/JUST-2021-0126

Article Views:218 Full article PDF

Abstract:
The electrocatalytic nitrogen reduction reaction (NRR) can transform nitrogen and protons from aqueous electrolytes to ammonia by using renewable electricity under ambient conditions, which is a promising technology to replace the Haber-Bosch process. However, this technology is extremely challenging as it requires highly active electrocatalysts to break the stable triple-bonds of N₂.With p bands,main-group s-block metals have been rarely explored in NRR compared with transition metals.Herein, we employ first-principles calculations to propose a Mg single atom catalyst as a promising high-performance electrocatalyst for NRR, where Mg atom is coordinated with four oxygen atoms within graphene (Mg-O₄). Our results reveal that N₂ can be efficiently activated on Mg-O₄ and reduced into NH₃ through the alternating mechanism. Moreover, ab initio molecular dynamics simulations demonstrate the Mg-O₄structure has high stability.

A novel amidoxime modified polyethylene nanofibrous membrane with high uranium adsorption capacity

YU Rui, WAN Caixia, CHEN Xin, LI Liangbin

2021, 51(11): 831-839. doi: 10.52396/JUST-2021-0088

Article Views:224 Full article PDF

Abstract:
The amidoxime modified polyethylene nanofibrous membrane (AO-PENFM) was prepared by a two-step graft polymerization method and an amidoximation reaction. Firstly, the hydroxyethyl acrylate (HEA) was grafted on polyethylene nanofibrous membrane (PENFM) via pre-radiation induced graft polymerization, then the acrylonitrile (AN) and acrylic acid (AA) were grafted on poly hydroxyethyl acrylate (PHEA) chains by ceric ammonium nitrate(CAN) initiated graft polymerization. Finally, an aminoximation reaction was performed to prepare the novel AO-PENFM adsorbent. This two-step graft method was used to construct a nanostructure adsorption layer with high specific surface areas on the surface of PENFM. The AO-PENFM adsorbent in a uranium solution of 12 ppm after 120 h adsorption performs an excellent adsorption performance of 338.14 mg/g. Simultaneously, the adsorption kinetics conforms to the intraparticle diffusion model and pseudo-second-order model. In addition, the adsorption isotherm data conform to the Langmuir isotherm model.

Summer thermal performance study on pipe-embedded PCM composite wall in existing buildings

CHEN Sarula, CHANG Tianxin, YANG Yang, PAN Chao, WU Yunfa

2021, 51(11): 840-856. doi: 10.52396/JUST-2021-0114

Article Views:256 Full article PDF

Abstract:
Pipe-embedded building envelope is a heavyweight thermo-activated building system (TABS) that has its pipe circuits inside the building envelope, which has been seldom studied in existing buildings. In this context, the pipe-embedded PCM composite wall (PEPCW) in which the pipe-embedded interlayer is relocated to the outside of the load-bearing layer and replaced by macro-encapsulation-based pipe-embedded PCM panel is proposed to address the retrofitting challenges.In this paper, the summer thermal performance and energy saving potential of PEPCW are evaluated through a validated mathematical model. The simulation tests verify the effectiveness of PEPCW in cooling load reduction, and the corresponding amplitude value of interior surface temperature and heat flux can be decreased by 1.1 ℃ and 9.9 W·m^-2, respectively. Besides, the parametric tests indicate that the pipe interval has a more obvious influence than PCM thickness, and the value of 300/30 mm (pipe interval/PCM thickness) is recommended. Furthermore, the effectiveness of PEPCW is proved to be satisfactory in the three different cities (i.e., Tianjin, Nanjing, and Guangzhou), and the maximum heat gain reduction (i.e., 39.30 kWh·m^-2) is observed in hot summer and warm winter region (i.e., Guangzhou). In addition, the influence of solar absorbance on conditioned space at different orientations can be remarkably reduced through PEPCW, and the reduction in the three sunny sides are relatively higher than the dark side (i.e., north). Overall, the proposed PEPCW presents a satisfactory thermal behavior in the cooling season and could contribute to the progress of energy saving retrofit in the vast existing buildings.

2021 Vol. 51, No. 11

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