In this study, NiMo catalysts that have different metal loadings in the range of ca. 28–106 µg cm−2 were electrodeposited on the Ti substrate followed by their decoration with a very low amount of Au-crystallites in the range of ca. 1–5 µg cm−2 using the galvanic displacement method. The catalytic performance for hydrogen evolution reaction (HER) was evaluated on the NiMo/Ti and Au(NiMo)/Ti catalysts in an alkaline medium. It was found that among the investigated NiMo/Ti and Au(NiMo)/Ti catalysts, the Au(NiMo)/Ti-3 catalyst with the Au loading of 5.2 µg cm−2 gives the lowest overpotential of 252 mV for the HER to reach a current density of 10 mA·cm−2. The current densities for HER increase ca. 1.1–2.7 and ca. 1.1–2.2 times on the NiMo/Ti and Au(NiMo)/Ti catalysts, respectively, at −0.424 V, with an increase in temperature from 25 °C to 75 °C.
In this work, 3D nickel-manganese (NiMn) bimetallic coatings have been studied as electrocatalysts for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in alkaline (1.0 M KOH) media and the HER in acidic (0.5 M H2SO4) media. The catalysts have been deposited on a titanium substrate (1 × 1 cm2) using low-cost and facile electrochemical deposition method through a dynamic hydrogen bubble template technique. The electrocatalytic performance of these fabricated catalysts was investigated by using Linear Sweep Voltammetry (LSV) for HER and OER at different temperatures ranging from 25 up to 75 °C and also was characterized by scanning electron microscopy (SEM) and inductively coupled plasma optical emission spectroscopy (ICP-OES). It was found that fabricated NiMn/Ti-5 electrocatalyst with Ni2+/Mn2+ molar ratio of 1:5 exhibits excellent HER activity in alkaline media with overpotential of 127.1 mV to reach current density of 10 mA cm−2. On the contrary, NiMn/Ti-1 electrocatalyst that fabricated with Ni2+/Mn2+ molar proportion of 1:1 and lowest Mn-loading of 13.43 µgcm−2 demonstrates exceptional OER activity with minimum overpotential of 356.3 mV to reach current density of 10 mA cm−2. The current densities increase ca. 1.8–2.2 times with an increase in temperature from 25 °C to 75 °C for both HER and OER investigation. Both catalysts also have exhibited excellent long-term stability for 10 h at constant potentials as well as constant current density of 10 mA cm−2 that assure their robustness and higher durability regarding alkaline water splitting.
Hydrogen generation via water splitting in alkaline media is the most promising, alternative, clean, and next-generation technology that can fulfill the future energy demands and overcome the challenge of global warming. The kinetics of hydrogen generation via water splitting through electrochemical process mainly rely on hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Material selection and material design are the keys to developing highly active, low-cost, and stable non-noble metal electrocatalysts but also are of great challenge. The Au(NiMo)/Ti-based catalysts were prepared via chemical and electrochemical methods in this study. Initially, the NiMo coatings on the Ti surface (1x1cm) were electrodeposited from a bath containing 0.01 M Na2MoO4 and 0.01, 0.1, and 0.5 M NiSO4 in an acidic condition. The process of electrochemical deposition was carried out at the current of 0.1 mA and 1 mAfor 3 min. The gold nanoparticles were deposited on the previously prepared NiMo/Ti electrodes by galvanic displacement through their immersion into an acidic Au-containing solution for 10s. The morphology and composition of the newly prepared catalysts have been investigated via SEM, XRD, EDS, and ICP-OES. The investigation of electrocatalytic properties of the prepared catalysts was performed by recording linear sweep voltammograms in 1M NaOH solution at a potential scan rate of 10 mVs-1 at 25-75⁰C temperature range. It was observed that the power densities for the newly prepared Au(NiMo)/Ti catalysts with the Au loading from 2 up to 4 µgAucm-2 were 1.3 to 1.8 times higher than using NiMo/Ti catalysts for HER. Acknowledgment This project has received funding from European Social Fund (project No 09.3.3-LMT-K-712-19-0138) under a grant agreement with the Research Council of Lithuania (LMTLT).
In this study, three-dimensional gold-nickel-molybdenum (Au(NiMo)) catalysts have been studied as catalysts for the oxygen evolution reaction (OER). The catalysts have been deposited on a titanium surface using electroplating and galvanic displacement techniques. The modification of NiMo with a low amount of Au crystallites in a range of 1.2– 5.2 μgAucm–2 results in enhanced activity for OER in the alkaline medium compared to respective binary un-modified NiMo catalysts. The current densities for OER increase ca.1.2–7.3 and 1.3–5.1 times with an increase in temperature from 25 up to 75°C using the prepared 3D binary NiMo/ Ti and Au(NiMo)/Ti catalysts, respectively.
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