Modulation Of Nickel And Cobalt Based Nanostructures By Lignin-derived Carbon Dots And The Investigation On The Performance Of Water Splitting

Water splitting provides a clean technique for obtaining high purity hydrogen and therefore is considered to the essential for the realization of hydrogen energy economy.Nickel and cobalt-based compounds are widely studied as catalysts for electrolytic water splitting due to their high intrinsic activity and the advantages in terms of reserves and price.However,compared with noble metal catalysts,their catalytic performance still leaves a certain gap and needs to be further improved.Due to their good electrical conductivity,high specific surface area and easily modifiable surface chemistry,carbon nanomaterials are widely used in improving the activity of the metal catalysts.Carbon dots are a class of carbon nanomaterials with a particle size of less than 10 nm.The excellent electron transport properties and ease of functionalization make its as suitable building blocks for electrocatalysts.The use of naturally distributed and abundant lignin for the preparation of carbon dots is an effective way to realize the high value utilization of wood resources.Lignin has a high carbon content and are usually wasted as by-products of the paper industry.In addition,it also is the only non-petroleum resource in nature that can provide renewable aromatic-based compounds.The conversion of lignin into functional carbon dots can turn waste into treasure and realize the recycling of resources.In this study,lignin was used as a carbon source to prepare carbon dots,and on this basis,it was compounded with three nickel and cobalt-based catalysts to develop three catalysts with excellent performance for water electrolysis.The work in this article was carried out in the following aspects:（1）N,S co-doped lignin-derived carbon dots（LCDs）were prepared by acid hydrolysis of 2-aminobenzenesulfonic acid and subsequent hydrothermal carbonization using lignin as carbon source.LCDs possesses uniform particle size,rich oxygen-containing functional groups and can emit bright blue-green fluorescence.（2）The Co₃O₄/LCDs catalyst was prepared by a simple calcination method.Co₃O₄ is loaded on the carbon sheets formed by the functional group interaction between LCDs,which improves the dispersion of the material and further optimizes the catalytic activity and stability.（3）NiCo₂O₄/LCDs catalysts with different morphologies were prepared under the control of LCDs.LCDs can not only endow NiCo₂O₄different morphologies,but also can regulate its electronic structure through coupling with NiCo₂O₄,thereby improving the OER performance of water splitting.The as-prepared catalyst with a nanosheet wrinkled structure not only exhibits excellent OER catalytic activity and stability in alkaline media,but also has excellent performance in simulated seawater and alkaline seawater.（4）LCDs modified Co-doped Ni₃S₂ catalysts were prepared in situ by a two-step hydrothermal method.Benefiting from the synergistic effect between LCDs and the Co-Ni₃S₂,the prepared composite catalyst exhibits enhanced HER performance for water splitting.On this basis,the two-electrode cell device constructed with NiCo₂O₄/LCDs can achieve overall water splitting at a low voltage and can operate stably for 12 h.