Multifunctional catalytic sites regulation of atomic-scale iridium on orthorhombic-CoSe_(2)for high efficiency dual-functional alkaline hydrogen evolution and organic degradation

The earth-abundant and high-performance catalysts are crucial for commercial implementation of hydrogen evolution reaction(HER).Herein,a multifunctional site strategy to construct excellent HER catalysts by incorporating iridium(Ir)ions on the atomic scale into orthorhombic-CoSe2(Ir-CoSe_(2))was reported.Outstanding hydrogen evolution activity in alkaline media such as a low overpotential of 48.7 mV at a current density of 10 mA cm^(-2)and better performance than commercial Pt/C catalysts at high current densities were found in the Ir-CoSe_(2) samples.In the experiments and theoretical calculations,it was revealed that Ir enabled CoSe_(2)to form multifunctional sites to synergistically catalyze alkaline HER by promoting the adsorption and dissociation of H_(2)O(Ir sites)and optimizing the binding energy for H^(*)on Co sites.It was noticeable that the electrolytic system comprising the Ir-CoSe_(2)electrode not only produced hydrogen efficiently via HER,but also degraded organic pollutants(Methylene blue).The cell voltage of the dual-function electrolytic system was 1.58 V at the benchmark current density of 50 mA cm^(-2),which was significantly lower than the conventional water splitting voltage.It was indicated that this method was a novel strategy for designing advanced HER electrocatalysts by constructing multifunctional catalytic sites for hydrogen production and organic degradation.

Supramolecular electrostatic self-assembly of mesoporous thin-walled graphitic carbon nitride microtubes for highly efficient visible-light photocatalytic activities

For efficient solar energy conversion,the morphology engineering of hollow graphitic carbon nitride(gC3 N4)is one of the promising approachs benefiting from abundant exposed active sites and short photocarrier transport distances,but is difficult to control on account of easy structural collapse.Herein,a facile supramolecular electrostatic self-assembly strategy has been developed for the first time to fabricate mesoporous thin-walled g-C3N4 microtubes(mtw-CNT)with shell thickness of ca.13 nm.The morphological control of g-C3N4 enhances specific surface area by 12 times,induces stronger optical absorption,widens bandgap by 0.18 e V,improves photocurrent density by 2.5 times,and prolongs lifetimes of charge carriers from bulk to surface,compared with those of bulk g-C3N4.As a consequence,the transformed g-C3N4 exhibits the optimum photocatalytic H2-production rate of 3.99 mmol·h^-1·g^-1(λ>420 nm)with remarkable apparent quantum efficiency of 8.7%(λ=420±15 nm)and long-term stability.Moreover,mtw-CNT also achieves high photocatalytic CO2-to-CO selectivity of 96%(λ>420 nm),much better than those on the most previously reported porous g-C3N4 photocatalysts prepared by the conventional hard-templating and soft-templating methods.

CsPbBr_(3)-DMSO merged perovskite micro-bricks for efficient X-ray detection

Inorganic perovskite wafers with good stability and adjustable sizes are promising in X-ray detection but the high synthetic temperature is a hindrance.Herein,dimethyl sulfoxide(DMSO)is used to prepare the CsPbBr_(3)micro-bricks powder at room temperature.The CsPbBr_(3)powder has a cubic shape with few crystal defects,small charge trap density,and high crystallinity.A trace amount of DMSO attaches to the surface of the CsPbBr_(3)micro-bricks via Pb-O bonding,forming the CsPbBr_(3)-DMSO adduct.During hot isostatic processing,the released DMSO vapor merges the CsPbBr_(3)micro-bricks,producing a compact and dense CsPbBr_(3)wafer with minimized grain boundaries and excellent charge transport properties.The CsPbBr_(3)wafer shows a large mobility-lifetime(μτ)product of 5.16×10^(-4)cm^(2)·V^(-1),high sensitivity of 14,430μC·Gyair^(-1)·cm^(-2),low detection limit of 564 nGyair·s^(-1),as well as robust stability in X-ray detection.The results reveal a novel strategy with immense practical potential pertaining to high-contrast X-ray detection.

开口扭曲片圆管强化传热与流动阻力特性模拟

在乙烯裂解管式加热炉的工业应用中,通过在炉管内加入扭曲片内构件,将管内流动由平推流转为旋转流,增大了切向速度的同时加强了流体对管壁的冲刷作用,达到强化传热的目的。在第二代扭曲片的基础上进行结构改进,采用RNG k-ε湍流模型模拟炉管内部的流动,对比分析了不同扭曲片结构管道内的纵向涡结构、阻力系数、努塞尔数、综合传热系数及速度矢量场与温度梯度场耦合协同情况。结果表明,沿管壁呈"狭缝"状开口的扭曲片结构增大了管内流动的旋流强度,降低了阻力损失;开口长度7 mm、宽度2 mm、间隔2 mm的扭曲片结构局部阻力系数是第一代的93.75%,比第二代增加了8.67%,但综合传热系数比第二代提高了1.56%,是光管的1.29倍,该结构提高了纵向涡的稳定性,强化了管道核心流体与管壁的动量、热量交换;而沿管道中心开口的扭曲片结构增大了局部阻力系数,造成局部损失增加。

压滤式水电解槽微通道内球凸-球凹结构绕流特性的模拟

压滤式水电解槽是电解水制氢过程中的关键设备,电解槽极板通道内设有球凸-球凹结构,其内部的水流分布直接影响通道内的电解液分布及传热状况,从而影响电解设备的稳定性。为研究压滤式水电解槽极板通道内的流场特性,采用RNG k-ε湍流模型对电解单元单极室内的流场进行了模拟,分析了流道内的涡旋情况及速度分布均匀性。结果表明,极板通道结构决定了涡旋产生的位置,从而影响流道内的速度分布,随入口流量增大,涡旋强度增大,扰动程度增强;水流速度分布具有对称性,球凸-球凹结构使速度分布具有波动性,且在不同球凸边缘均出现速度峰值;不同流量下流道内沿流动方向的速度分布均匀性指数不同,球凸-球凹结构的扰流作用能改善速度分布均匀性,但不同流量时的改善效果不同。

热风混合器内部流场的数值模拟与结构改进

对热风混合器进行了结构改进,采用标准k-ε模型对改进前后热风混合器内部的流场和温度场分布进行了数值模拟。结果表明,相比于传统结构,对称T型双热风入口结构的混合器内部流场分布对称性较好,气流均匀性提高,渐缩型出口设计改善了回流问题,加设分散挡板增强了换热效果。三方面的结构改进使混合器出口气流的温度均匀性有效改善,减小了能量消耗,提高了热混合效率。

多组扭曲片排布方式对乙烯裂解炉管内产物收率的影响

针对乙烯裂解炉炉管内置入不同组数扭曲片对裂解产物收率的影响进行数值模拟,选用石脑油为裂解原料,得到不同管型的温度分布、乙烯等产物质量分数的分布情况。结果表明,扭曲片可有效降低管壁与核心流体间的温度梯度,且出口段置入3组扭曲片的炉管换热效果最佳;炉管中乙烯与丁二烯的产率沿轴向距离线性增加,丙烯产率在反应后期的出口段下降;入口段置入2组、出口段置入3组扭曲片的L2R3型炉管具有较高的三烯收率,是光管的1.29倍。

极板凹凸结构形状对电解槽内部流动特性的影响

目前压滤式水电解槽极板普遍采用球形凹凸组合结构,目的是能够增强流动的扰动程度,使电解液分布更加均匀。为了进一步改善流场分布,将五种不同形式的凹凸组合结构与电解单元极板结构相结合,采用数值模拟方法分析并比较了不同凹凸组合结构通道内部的流动特性和流场分布特点。结果表明,五种结构通道内的速度分量uz均存在负速度分布区域,且该区域内的湍动能值较大;局部涡旋均表现为凹陷结构边缘处向凹陷内部发展的涡旋运动,涡旋流动细节与凹凸结构形式密切相关;平均涡通量及涡量值的分布表明凹凸结构主要影响局部区域的涡旋强度,对整体流动影响较小;流场分布均匀性与凹凸结构迎风面的形状尺寸等因素有关,其中Case D泪滴形结构的流场分布均匀性最好。