Search

Converting biomass‐derived 5‐hydroxymethylfurfural (HMF) into high‐valued 2,5‐dihydroxymethylfurfural (DHMF) via electrocatalytic hydrogenation (ECH) technology has been widely regarded as one of the most economical and eco‐friendly routes. The high selectivity and activity depend on the reasonable regulation of the adsorption and activation of adsorbed hydrogen (H*) and HMF on the surface of the electrocatalyst. Herein, we report nanoflower‐like CuFe‐based electrocatalysts on copper foam (CF) substrates (CuFeOx/CF). DHMF was achieved on the optimal CuFeOx/CF with a selectivity of 93.3 % and a yield of 90.1 %. The H*, HMF and product were observed by in situ attuned total reflection Fourier transform infrared spectroscopy (ATR‐FTIR). Moreover, in situ Raman spectra discloses the reconstruction of catalyst into CuFe‐bimetal with low valence state. Density functional theory (DFT) calculations demonstrate that introducing Fe plays a role in regulating the electronic structure of Cu sites, which facilitate the generation of H* and adsorption of HMF, thus hampering the occurrence of dimerization. This study provides an innovative idea for the rational design of non‐precious bimetallic electrocatalysts for ECH to produce high‐valued chemicals. [ABSTRACT FROM AUTHOR]

Electrocatalytic glycerol oxidation reaction (GOR) stands out as an economical and prospective technology to replace oxygen evolution reaction for co‐producing high‐valued chemicals and hydrogen (H2). Regulating the adsorption of glycerol (GLY) and hydroxyl (OH) species is of great significance for improving the GOR performance. Herein, a hierarchical p–n heterojunction by combining Co‐metal organic framework (MOF) nanosheets with CuO nanorod arrays (CuO@Co‐MOF) is developed to realize the optimization on GOR. Specifically, CuO@Co‐MOF electrode exhibits superior performance with a conversion of 98.4%, formic acid (FA) selectivity of 87.3%, and Faradaic efficiency (FE) of 98.9%. The flow‐cell system with the bifunctional CuO@Co‐MOF electrode for pairing GOR with the hydrogen evolution reaction (HER) reveals better energy conversion efficiency. Experimental results and theoretical calculations unravel the redistributed electric field by introducing Co‐containing species that contribute to the improved performance, which not only enhances the OH adsorption but also modulates the excessive GLY adsorption of CuO, thus reducing reaction energy barriers of FA desorption. Simultaneously, finite element analysis reveals that the novelty hierarchical structure can increase the concentration of OH− and facilitate the mass transfer of OH− in the solution. [ABSTRACT FROM AUTHOR]

Highly efficient and inexpensive electrocatalysts for oxygen evolution reaction (OER) are extensively studied for water splitting. Herein, a unique bimetallic nanocomposite CoNi(OH)2@NiCo2S4 nanosheet arrays derived from metal-organic-frameworks (MOFs, CoNi-ZIF) is simply fabricated on Ni foam, endowing large specific surface area and outstanding electrical conductivity. Compared with their single-metallic counterparts, the bimetallic composite displays dramatically low overpotential and small Tafel slope as well as outstanding catalytic stability. The overpoptential at 20 mA cmâˆ'2 for CoNi(OH)2@NiCo2S4 is only 230 mV in comparison with Ni(OH)2@Ni3S2 (266 mV), Co(OH)2@Co3S4 (294 mV) and RuO2 (η  = 302 mV). First-principle calculations based on density functional theory (DFT) are carried out and reveal that the introduction of Ni in Co(OH)2 helps lowered the energy difference of Î" G OOH*â€"Î" G O*, and thereby boosting the OER reactivity. This study provides an effective approach for the rational construction of low-cost metal hybrids. [ABSTRACT FROM AUTHOR]

A full-scale measurement of wind characteristics atop a high-rise building (with a height of 115 m) was conducted during the passage of Typhoon Sarika on 18 October 2016. Wind field characteristics, wind speed, and wind direction atop the building were recorded synchronously, and turbulence intensity, turbulence integral scale, gust factor, and power spectrum were investigated. Meanwhile, the time and frequency domain characteristics of the wind field were analyzed. The stationarity test results of Typhoon Sarika at different time steps are researched in a runs test. And the time-frequency analysis of non-stationary samples of fluctuating wind speed are conducted by wavelet transform, the measured data are valuable for the wind-resistant design of high-rise buildings in typhoon-prone regions. [ABSTRACT FROM AUTHOR]

On 18 October 2016, the wind-induced effects of a high-rise building with square section was measured by the monitoring system in Haikou of China during Typhoon Sarika. The wind characteristics atop the building and the time-history responses of the translational and rotational accelerations on different floors were measured by the monitoring system; the first three modal parameters were identified according to the measured acceleration. The results show that the combinations of the cross spectral density function, phase spectrum, and coherence function can clearly judge the phase of the measured floors in the frequency resonance area as well as its modal frequencies at the first three orders. The modal frequencies at the first three orders decrease linearly with the growth of mean wind speed within the range of 0~20m/s. The estimation formula of the modal frequencies of high-rise buildings considering the influences of different wind speeds is put forward, which is expected to fill the gap in the existing specification for the quantitative analysis of the influences of wind-loads on the fundamental frequencies of high-rise buildings. [ABSTRACT FROM AUTHOR]