Tikrit Journal of Pure Science Vol. 28 (1) 2023 66 Tikrit Journal of Pure Science ISSN: 1813 – 1662 (Print) --- E-ISSN: 2415 – 1726 (Online) Journal Homepage: http://tjps.tu.edu.iq/index.php/j Nickel and titanium metals for the hydrogen evolution reaction in water electrolysis: A comparative study Aya Awas Saad, Farkad Ali Lattieff Department of energy engineering, college of energy, University of Baghdad, Baghdad, Iraq https://doi.org/10.25130/tjps.v28i1.1267 A r t i c l e i n f o. Article history: -Received: 3 / 10 / 2022 -Accepted: 30 / 10 / 2022 -Available online: 20 / 2 / 2023 Keywords: Alkaline electrolysis, Titanium metal, Nickel metal, Hydrogen production, High voltage, power ohmic loss, SEM, EDX. Corresponding Author: Name: Aya Awas Saad E-mail: Tel: ©2022 COLLEGE OF SCIENCE, TIKRIT UNIVERSITY. THIS IS AN OPEN ACCESS ARTICLE UNDER THE CC BY LICENSE http://creativecommons.org/licenses/by/4.0/ ABSTRACT This work investigated experimentally and theoretically the I-V output change, the hydrogen production, and the efficiency of Ti and Ni metals as substrates for water electrolysis systems. To make optimization between the candidate electrodes, seven configurations of Ni-Ti, Ti-Ti, and Ti-Ni with three KOH solutions of 10, 20, and 30 % wt (weight KOH gm/weight water gm) as an electrolyte were conducted as a cathode-anode system. The selected electrodes were examined by scanning electron microscopy (SEM) and energy dispersive (EDX) to study their surface morphology and element composition. According to experimental findings, when the cell voltage of 5 V is applied, the hydrogen production from the Ti-Ti (20%KOH) and Ni-Ti (20% and 30% KOH) electrodes reach an optimal value of 6331 cm 3 , which is significantly higher than the hydrogen production from the other electrodes at the same voltage. The Ni-Ti electrode with a 10% KOH content had the maximum efficiency (72%), and the Ni-Ti electrode with a 30% KOH content had the lowest efficiency (61%), both at 3V for the cell. This study demonstrates that the Ni-Ti system can be the most suitable source for hydrogen evolution rather than the other arrangements when the appropriate mixing ratio of 20 % KOH solution is prepared before the electrolysis process. 1- Introduction Renewable energy applications have become an integral part of present-day living. With the changing lifestyle, the demand and supply of renewable energy systems have gradually increased. As one of the renewable energy sources, a water electrolysis unit powered by photovoltaic cell electricity is the most common means for hydrogen generation purposes [1- 3]. Hence, alkaline water electrolysis can be a good alternative to conventional steam reforming [4-9]. However, it is not commercially competitive with the steam reforming method [10]. Further development research is still required for improvement in the existing design to increase the catalytic activity of the cathode and the anode, consequently increasing the overall performance of the system and reducing the system unit cost [11-15]. Despite their high resistivity toward oxidation, expensive noble’s materials such as platinum give limitations in the water-splitting technology due to their high price and environmental issues such as corrosion [16-18]. To reduce the overall cost, diaphragm issues, and its complex assembly, an alternative of growing interest is diaphragm-free AEC. These types of electrolyzers use water-electrolytes of potassium hydroxide (KOH) or sodium hydroxide (NaOH) in a range of 20-30 % wt [19]. The need for integration between Ni and Ti metal electrodes as a cathode-anode system seems consistent with the alkaline electrolyte of the KOH solution. Hydrogen generation using Ti and Ni metal electrodes via water electrolysis has been the subject of interest to several research works [20-25]. The overpotential of Ni element for hydrogen and oxygen reaction was reported by Alejandro et al. [26]. This study was carried out using a direct-current powered electrolysis system of high KOH concentration solution. Raney Ni and stainless steel 316L were used as the cathode and anode, which were inserted to run for one month in a locally monopolar cell at 300