Rong Shang,Qizhao Zhang,Peng Lin,Bang Gu,Qinghu Tang,Qiue Cao,Wenhao Fang
Direct oxidative coupling of alcohols and amines is an environmental-benign and atomic-economy approach for imine synthesis. We disclosed that UiO-66 framework successfully confined Ru to single-atom scale with assistance of oxophilic Zn 2+ promoter. This RuZn@UiO-66 catalyst showed a highest TOF of 78 h -1 among all Ru catalysts in literature and attained > 99% yield to benzylideneaniline in the model reaction in an O 2 atmosphere at a low temperature without alkaline additives. In addition, this catalyst demonstrated satisfying gram-scale imine synthesis, wide substrate scope and stable reusability. Kinetic investigations and in situ characterizations allowed getting insights to active sites, amphoteric carrier and reaction mechanism. Dynamic interactions between Ru and Zn based on their ratios induced electron-deficient Ru 0 active sites promoted by oxophilic Zn 2+ species. Hence, primary alcohols can be efficiently converted to the corresponding aldehydes using molecular O 2 , i.e. , the rate-determining step. Besides, Zr 4+ -O 2- pairs on UiO-66 provided adequate acidic-basic sites for the tandem catalysis.
Hang Wang,Han Xu,Fei Yang,Yan Qing,Fuxiang Chu,Yiqiang Wu,Sheng Ye,Fuquan Xiong
Local electric fields of the electrocatalysts can modulate adsorbate binding energies based on their polarizability and dipole moment, which directly influence the catalytic performance. Nevertheless, implementing the prevailing strategy remains challenging due to the scarcity of active sites and sluggish catalytic kinetics. Herein, a continuous heterogeneous-curvature nanoreactor (HeterC-LCS) is created to enhance local electric fields by optimizing the uniform-nanocurvature with tip effects. The H + concentration and H 2 O transmission rate of HeterC-LCS are improved by about 2.1 and 1.7 times that of the homogeneous curvature structure (HomoC-LCS) during the hydrogen evolution reaction (HER) process. Besides, HeterC-LCS demonstrates a rapid kinetics of intermediate transformation and an extremely low energy barrier. Such HeterC-LCS depicts a lowest overpotential of 9.2 mV at 10 mA cm −2 , which outperforms all known carbon- and Ru-based electrocatalysts. And the mass activity is approximately 60 times that of commercial Pt/C. This work proposes a novel strategy of uniform-nanocurvature optimized by tip effects toward industrially electrocatalytic HER.
Qi Hu,Guomin Li,Xiaowan Huang,Ziyu Wang,Hengpan Yang,Qianling Zhang,Jianhong Liu,Chuanxin He
Regulation of the electronic structures of metal centers represents a robust strategy for enhancing the activity of electrocatalysts. Herein, we report the crafting of hybrid electrocatalysts comprising both single atomic Ru (SA-Ru) and Ru nanoparticles (NPs) supported on porous N-doped carbon (PC), in which the electronic structures of SA-Ru were effectively optimized by nearby Ru NPs to achieve great enhancement of the hydrogen evolution reaction (HER). The resulting SA-Ru/Ru NPs/PC displayed ultrahigh activity for HER in 1 M KOH with a mass activity of 4.2 mA μgRu−1 at −0.07 V vs. RHE; this activity was 14 times that of commercial Pt/C, representing the largest reported value among the Pt-free electrocatalysts. In addition to the ultrahigh activity, the composite possessed the outstanding stability of 24 h and rapid HER kinetics (i.e. Tafel slope: 31.8 mV dec−1). The experimental and theoretical results matched well with each other and unambiguously indicated that the control over the electronic structures of SA-Ru and the advantageous PC support (i.e. its hierarchical porous nanostructures and superhydrophilic surface) jointly contributed to the exceptional performance.
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