Exploring The Influence Of Sodium Perchlorate Solution Concentration On The Pk_w Of Liquid Water Based On DFTMD/Machine Learning Potential

Electrolytes play an extremely important role in all kinds of batteries,and the concentration of electrolytes has crucial impact on the battery properties.At present,most batteries use non-aqueous electrolytes.However,non-aqueous electrolytes are expensive and waste.Also,non-aqueous electrolytes will do harm to the ecological environment.In response to the call of green chemistry,people turn their attention to aqueous electrolytes.It has been reported that aqueous electrolytes have several advantages and are under good development.In supercapacitors,the electrochemical window can even reach 2.8V when high-concentration sodium perchlorate electrolyte is applied.Generally,the main component of aqueous electrolyte is inorganic salt.Thus,compared to non-aqueous electrolytes,aqueous electrolytes are cheap,easy to obtain,and environmentally friendly.However,in order to explore the properties of aqueous electrolytes,it is necessary to explore its microstructure.Generally,the main component of aqueous electrolyte is inorganic salt.The research direction of this project is the influence of the concentration of the inorganic salt(NaClO4)solution on the ionization ability of water molecules,that is,pKw.In this project,the value of pKw can be calculated by density functional theory molecular dynamics(DFTMD).This research topic uses DFTMD method to study the effect of sodium perchlorate solution concentration on the ionization ability of water molecules.In physical chemistry,the ionization of water molecules is an important property.Liquid water is a very weak electrolyte,and the ionization ability of it at room temperature is very weak.Generally,only about 10’7 mol of water molecules are ionized in 1L(55.6mol)liquid water.If you want to change the ionization ability of water molecules,you can change the external conditions of water,such as temperature,pressure,and composition of solution etc.This research focuses on the influence of the concentration of inorganic salt solution(NaClO4)on the pKw values of liquid water.Three concentrations of NaClO4 including 0.87 mol/L,5.20 mol/L and 8.70 mol/L are simulated to obtain pKw values.The results show that as the concentration of NaClO4 solution increases,the ionization capacity of water decreases,that is,the pKw value increases.After analysis,the occurrence of this phenomenon is closely related to the destruction of the hydrogen bond network of liquid water.And the change trend is consistent with the experimental values.However,due to the limitations of the DFTMD method and expensive computing resources,the time scale of calculations is within 10-100 ps,which may make it impossible to get convergence results.In addition,when using the thermodynamic integral method,the number of potential energy surfaces inserted in the method itself is not enough,which will lead to errors in the calculation results.Therefore,it is necessary to use machine learning potential to reduce the calculation error.From the calculation results,machine learning potential can significantly extend the calculation time scale,increase the number of inserted potential energy surface,improve the accuracy of calculation,and reduce the error of thermodynamic integral value of water molecule/hydrogen hydrate ion.