Type III deep eutectic solvents (DES) have been extensively studied as a green electrodeposition solvent due to their wide potential window and degradability. The preparation of nickel-based coatings from DES commonly uses nickel chloride as the main precursor of Ni²⁺, but it generates harmful chlorides during long-term electrodeposition. This article uses nickel sulfate as the main precursor of Ni²⁺ to investigate the effects of boric acid and water on the deposition of Ni/TiO₂ composite coatings from 1:2 choline chloride (ChCl) - ethylene glycol (EG) DES. It is found that light green Ni (OH)₂ crystalline solid and solvent decomposition products such as trimethylamine appeared in the coating. Interestingly, the acidic environment created by boric acid can inhibit the formation of Ni(OH)₂ and the decomposition of solvents. Moreover, adding water to DES can reduce its viscosity and increase its conductivity, which will speed up the reduction of nickel ions. Water can change the complex form of Ni²⁺ in DES and reduce the average crystallite size of the coating. In this paper, the mechanism of the effect of boric acid and water on the deposition behavior of Ni²⁺ in DES is analyzed, and the deposition model is established, which provides a theoretical and experimental reference for green preparation of composite coatings.

III型深层共晶溶剂（DES）由于其潜在的窗口宽和可降解性而被广泛研究为绿色电沉积溶剂。由DES制备镍基涂层通常使用氯化镍作为Ni ²⁺的主要前体，但在长期电沉积过程中会生成有害的氯化物。本文以硫酸镍为主要的Ni ²⁺前驱体，研究了硼酸和水对1：2氯化胆碱（ChCl）-乙二醇（EG）DES沉积Ni / TiO ₂复合涂层的影响。发现浅绿色的Ni（OH）₂结晶的固体和溶剂分解产物（如三甲胺）出现在涂层中。有趣的是，由硼酸产生的酸性环境可以抑制Ni（OH）₂的形成和溶剂的分解。此外，在DES中加水可降低其粘度并增加其电导率，这将加快镍离子的还原速度。水可以改变DES中Ni ²⁺的复杂形式，并减小涂层的平均微晶尺寸。本文分析了硼酸和水对DES中Ni ²⁺沉积行为的影响机理，建立了沉积模型，为复合涂层的绿色制备提供了理论和实验参考。