Synthesis Of Carbon Quantum Dots And Their Corrosion Inhibition Performance

Carbon quantum dots,as a new type of carbon nanomaterials,have the advantages of low toxicity,simple preparation,small particle size,easy surface adjustment,rich functional groups and so on,it has the advantages of becoming a green and efficient corrosion inhibitor.Therefore,three kinds of environment-friendly carbon quantum dots were synthesized,and conducted reserch on their corrosion resistance and inhibition mechanism in different corrosive media.The specific studies are as follows:1.Nitrogen and sulfur doped carbon quantum dots were synthesized from p-aminosalicylic acid and thiourea.The electrochemical results show that N/S-CDs can effectively inhibit the corrosion of AZ31B magnesium alloy in 3.5wt%Na Cl solution,and it is a mixed type of corrosion inhibitor.When the concentration of N/S-CDs is 50mg/L,the inhibition efficiency is 86.6%.The adsorption of N/S-CDs on the surface of magnesium alloy follows the Langmuir adsorption equation,and the standard Gibbs free energy of adsorption is-32.1 k J/mol,the adsorption is both physical adsorption and chemical adsorption.X-ray photoelectron spectroscopy results show that the amino groups in N/S-CDs form N-Mg coordination bonds with Mg atoms,the inhibitor has a strong adsorption on the surface of magnesium alloy.The results of quantum chemistry and molecular dynamics simulation show that the adsorption active sites of the inhibitor are located on the benzene ring and amino group,which have strong adsorption ability with the steel.The interaction energy between corrosion inhibitor and magnesium alloy（-987.37 k J/mol）is far greater than that of water（-8.89 k J/mol）.N/S-CDs can form a firm adsorption film on the magnesium alloy surface,thus effectively inhibiting the corrosion of magnesium alloy.2.Nitrogen doped carbon quantum dots（N-CDs）were synthesized from p-aminosalicylic acid and L-histidine.The electrochemical results show that N-CDs can effectively inhibit the corrosion of Q235 steel in 1 mol/L HCl solution,and it is a mixed type of corrosion inhibitor.When the concentration of N-CDs is 50 mg/L,the inhibition efficiency is 91.5%.The results of weight loss method show that the corrosion inhibition efficiency was 93.5%when the steel was immersed in the medium for 60 h,which had a long-term protective effect on the steel.The adsorption of N-CDs on the surface of steel follows the Langmuir adsorption equation,and the standard Gibbs free energy of adsorption is-33.63 k J/mol,the adsorption is both physical adsorption and chemical.The results of quantum chemistry and molecular dynamics simulation show that the adsorption active sites of the inhibitor are located on the benzene ring,imidazole ring and amino group,which have strong adsorption ability with the steel.The interaction energy（-553.43 k J/mol）is far greater than that of water（-18 k J/mol）.N-CDs can form a firm adsorption film on the steel surface,thus effectively inhibiting the corrosion of steel.3.Imidazole modified carbon quantum dots（FM-CDs）were synthesized from carbon quantum dots and（1H-Benzo[d]imidazol-2-yl）methanamine.The electro-chemical results show that FM-CDs can effectively inhibit the corrosion of copper in0.5 mol/L H₂SO₄ solution,and it is a cathodic corrosion inhibitor.When the concentration of FM-CDs is 50 mg/L,the inhibition efficiency is 89.2%.The adsorption of FM-CDs on the surface of copper follows the Langmuir adsorption equation,and the standard Gibbs free energy of adsorption is-32.72 k J/mol,the adsorption is both physical adsorption and chemical.The temperature can also affect the inhibition of FM-CDs on copper,increasing temperature accelerates the corrosion of copper,but FM-CDs still has a strong inhibition in the range of 25-45℃.At 45℃,the corrosion inhibition efficiency is still 79.0%.The results of quantum chemistry and molecular dynamics simulation show that the adsorption active sites of FM-CDs are located on the benzene ring,imidazole ring and amino group,which have strong adsorption ability with the copper.The interaction energy（-987.37 k J/mol）is far greater than that of water（-8.89 k J/mol）.FM-CDs can form a firm adsorption film on the copper surface,thus effectively inhibiting the corrosion of copper.