## 1 Introduction  
The production of hydrogen through water electrolysis, powered by renewable energy sources such as solar and wind, is considered a fundamental step toward achieving sustainable hydrogen production. Given the high energy input required for this process, developing cost-effective and efficient electrocatalysts becomes a major priority for industry. Nickel, known for its excellent activity in alkaline media, is a widely adopted material in electrode assemblies for alkaline water electrolyzers [1, 2, 3].  
Alkaline water electrolysis (AWE) remains one of the most widely applied methods for large-scale hydrogen generation, due to its operational simplicity, lower materials cost compared with proton exchange membrane (PEM) systems and extended tolerance to electrolyte impurities. However, the performance of AWE is still constrained by the relatively slow kinetics of HER and especially OER, thus necessitating additional strategies to improve the overall system's efficiency beyond the catalyst design.  
Moreover, the reaction rates of hydrogen evolution (HER) and oxygen evolution (OER) can be notably altered by introducing trace quantities of organic compounds into the electrolyte. Depending on their chemical nature, such additives may enhance or hinder the overall performance of the electrochemical setup [4; 5; 6]. Substances such as alcohols, ketones and organic acids are amongst those that could interact with the electrolysis system, especially because their incidental presence in industrial environments is not uncommon. For example, these molecules could effectively become adsorbed on the nickel electrode surface with some molecules experiencing potential-dependent surface electro-oxidation and electroreduction processes [7; 8; 9; 10; 11; 12], possibly affecting the rates of the water electrolysis process.  
On the other hand, the suitable employment of organic electrolyte additives might result in facilitated electrode reaction rates and, thus, in the enhanced performance of the green hydrogen and oxygen production processes. Among the various investigated organic additives, acetone stands out due to its strong hydrogen bonding with water and its known ability to lower surface tension, which may directly affect the kinetics of gas evolution processes [13; 14; 15]. Despite its promising features, the electrochemical behaviour of acetone in nickel-based systems remains largely unexplored. This knowledge gap is particularly relevant when considering nickel's dominance in industrial AWE stacks and the growing interest in the low-cost process's enhancement without the introduction of complex electrode modifications.  
This work follows an introductory article [16] on the influence of acetone on hydrogen and oxygen evolution reactions at a polycrystalline platinum electrode in 0.1 M NaOH, as reported in a recent study conducted by this research group. By investigating cyclic voltammetry (CV) and impedance spectroscopy (EIS) characteristics, the authors of this work seek to elucidate how acetone additions [with (CH\({}_{3}\))\({}_{2}\)C=O concentrations ranging from 1.0 \(\times\) 10\({}^{-7}\) to 1.0 \(\times\) 10\({}^{-3}\) M] could influence the kinetics of the HER and OER processes on the surface of a commonly used Ni catalyst material in alkaline water electrolysis. In this respect, the obtained results are markedly important for industrial alkaline water electrolysis applications.