Controllable defect engineering based on cobalt metal-organic framework for boosting oxygen evolution reaction

Defect engineering on metal-organic frameworks(MOFs)provides high flexibility to rationally design advanced oxygen evolution reaction(OER)catalysts with low overpotential and high stability.However,fundamental understanding the effect of defect concentration on catalytic OER activity is still quite ambiguous.Herein,the Co-MOF-Dx catalysts with regulated oxygen defects concentration are deliberately constructed via coupling one-pot solvothermal synthesis with NaBH_(4)chemical reduction process.Experimental findings propose that the oxygen defect concentration within Co-MOF-Dx gradually increases with raising the NaBH_(4)content,which could provide a flexible platform to tailor the electronic structure around active Co site and optimize adsorption/desorption capacity of oxygen intermediates.When the introduction content of NaBH_(4)is up to 5 mg,the resulting abundant unsaturated coordination defects could endow the Co-MOF-D5 catalyst with optimized electronic structure and more exposed active sites for improving charge transfer and adsorption/desorption capacity.It is found that the optimized Co-MOF-D5 can drive the current density of 10 mA cm^(-2)only at a low overpotential of 300 mV with the small Tafel slope of 53.1 mV dec^(-1)in alkaline medium.This work sheds light on the way for the development of high-performance MOF catalysts via modulating defect concentration.

Molecular dynamics simulation of latent track formation in α-quartz

The latent ion track in α-quartz is studied by molecular dynamics simulations. The latent track is created by depositing electron energies into a cylindrical region with a radius of 3nm. In this study, the electron stopping power varies from 3.0keV/nm to 12.0keV/nm, and a continuous latent track is observed for all the simulated values of electron stopping power except 3.0keV/nm. The simulation results indicate that the threshold electron stopping power for a continous latent track lies between 3.0keV/nm and 3.7 keV/nm. In addition, the coordination defects produced in the latent track are analyzed for all the simulation conditions, and the results show that the latent track in α-quartz consists of an O-rich amorphous phase and Si-rich point defects. At the end of this paper, the influence of the energy deposition model on the latent track in α-quartz is investigated. The results indicate that different energy deposition models reveal similar latent track properties. However, the values of the threshold electron stopping power and the ion track radius are dependent on the choice of energy deposition model.