[en] Water electrolysis using renewable energy sources such as solar and wind power has the advantage of producing hydrogen with high efficiency and zero emissions. Solid polymer electrolyte water electrolysis (SPEWE) is divided into anion exchange membrane electrolysis (AEMWE) carried out in an alkaline environment and proton exchange membrane electrolysis (PEMWE) carried out in an acidic environment. Research on the electrocatalysts used in these electrolysis procedures has focused on the development of transition metal-based catalysts with catalytic activity, high stability, and low cost that can replace the currently used noble-metal based electrocatalysts. Among the various electrocatalyst fabrication methods, electrodeposition can be used to fabricate catalysts in a simple manner at low cost and high purity. In addition, catalysts can be directly electrodeposited onto a substrate such as a gas diffusion layer, simplifying the electrode fabrication process and readily enabling the advantageous control of the physical, chemical, structural, and compositional properties of the catalyst. In this paper, we summarize the characteristics and structures of the water electrolysis catalysts prepared by the electrodeposition method based on recent research studies that suggest their applicability to practical water electrolysis systems in the future.

[en] An investigation has been carried out on the factors which affect the response reading of thermoluminescent dosimeters (TLD-100) loaded with thin material in high energy photon. The aim of the study was to assess the energy response of TLD-100 to the therapeutic ranges of photon beam. In this technique, TLD-100 (abbreviated as TLD) chips and three different thin material (Tin, Gold, and Tissue equivalent plastic plate) which mounted on the TLD chip were used in the clinical photon beam. The thickness of each metal plates was 0.1 mm and TE plastic plate was 1 mm thick. These compared with the photon energy dependence of the sensitivities of TLD (normal chip), TLD loaded with Tin or Gold plate, for the photon energy range 6 MV to 15 MV, which was of interest in radiotherapy. The enhancement of surface dose in the TLD with metal plate was clearly detected. The TLD chips with a Gold plate was found to larger response by a factor of 1.83 in 10 MV photon beam with respect to normal chip. The sensitivity of TLD loaded with tin was less than that for normal TLD and TLD loaded with Gold. The relative sensitivity of TLD loaded with metal has little energy dependence. The good stability and linearity with respect to monitor units of TLD loaded with metal were demonstrated by relative measurements in high energy photon (6 - 15 MV) beams. The TLD laminated with metals embedded system in solid water phantom is a suitable detector for relative dose measurements in a small beam size and surface dose

[en] A 20 wt % Pt/C is fabricated and characterized for use as the cathode catalyst in a polymer electrolyte membrane fuel cell (PEMFC). By using the polyol method, the fabrication process is optimized by modifying the carbon addition sequence and precursor mixing conditions. The crystallographic structure, particle size, dispersion, and activity toward oxygen reduction of the as-prepared catalysts are compared with those of commercial Pt/C catalysts. The most effective catalyst is obtained by ultrasonic treatment of ethylene glycol-carbon mixture and immediate mixing of this mixture with a Pt precursor at the beginning of the synthesis. The catalyst exhibits very uniform particle size distribution without agglomeration. The mass activities of the as-prepared catalyst are 13.4 mA/mgPt and 51.0 mA/mgPt at 0.9 V and 0.85 V, respectively, which are about 1.7 times higher than those of commercial catalysts

[en] Ni-P catalysts with various compositions were fabricated by pulse electrodeposition in pursuit of highly efficient and durable hydrogen evolution via proton exchange membrane water electrolysis. Pulse electrodeposition enabled the preparation of a Ni-P catalyst with a high portion of P, thereby conferring acid-resistant properties to the catalyst. Specifically, precise control of the deposition potential made it possible to leach Ni from bulk Ni-P and thus to vary the composition. With greater P incorporation, the catalyst became amorphous. The activity of the as-prepared Ni-P catalysts for the hydrogen evolution reaction (HER) in acidic medium was evaluated by cyclic voltammetry, confirming the strong dependence of the activity on the composition. The Ni-P catalyst with a bulk composition of Ni₇₈P₂₂ exhibited the best HER activity with an overpotential of 105 mV at −10 mA cm⁻². The current density of the single cell with the electrodeposited Ni₇₈P₂₂ cathode and electrodeposited IrO₂ anode was 1.31 A cm⁻² at 2.0 V_cell. Compared to reported values for other non-Pt or Pt cathodes for electrolysis, the electrolyzer with the Ni₇₈P₂₂ cathode strongly outperforms the non-Pt cathodes, and the performance is more than a half of that of the Pt cathode.

[en] Pt electrocatalysts in high-temperature proton exchange membrane fuel cells (HT-PEMFCs) containing phosphoric acid (PA)-doped polymer membranes are prone to poisoning by leaked PA. We performed a preliminary density functional theory (DFT) study to investigate the relationship between the electronic structure of Pt surfaces and their adsorption of PA. Excess charge on Pt was found to weaken its bonding with the oxygen in PA, thus presenting a strategy for the fabrication of PA-resistant catalyst materials. Consequently, PtCu-alloy catalysts with various compositions were prepared by electrodeposition. The morphologies and crystalline structures of the alloys were strongly dependent on alloy composition. Moreover, the Pt atoms in the PtCu-alloy catalysts were found to be in an electron-rich state, similar to that of the excessively charged Pt simulated in the DFT study. As a result, the oxygen reduction reaction activities of the PtCu-alloy catalysts were superior to that of a Pt-only catalyst, regardless of the presence of PA. In the absence of PA, the higher activity of the PtCu-alloy catalysts was ascribable to conventional alloying effects, while the increased activity in the presence of PA was largely due to the enhanced resistance to PA poisoning. Therefore, PtCu-alloy catalysts easily prepared by electrodeposition were found to be strong candidate materials for HT-PEMFC electrodes.

[en] Highlights: • Unravel the importance of catalysts layer structure in PEMWE. • Present an efficient strategy to construct hierarchical and defective RuO₂. • The RuO₂-NS/CF demonstrated an outstanding performance and stability for acidic OER. • The RuO₂-NS/CF exhibited excellent performance in PEMWE single cell. The use of proton exchange membrane water electrolyzers (PEMWEs) is severely limited by large overpotentials and the low stability of their anode catalysts. The majority of the state-of-the-art anode catalysts have been tested in half-cells; however, it is highly desirable to design an anode catalyst that can be effectively employed in a real electrolyzer. Herein, a new structural design strategy is proposed as an effective pathway for constructing efficient and stable PEMWE anodes. The developed self-standing electrode with hierarchical structure comprises porous and defective RuO₂ nanosheets aligned on carbon fiber (RuO₂-NS/CF) with several structural advantages, including large electrochemically active surface area, abundant defects, and exposed atoms/edges, and enhanced mass transfer capacity. Therefore, RuO₂-NS/CF exhibits outstanding performance and durability for oxygen evolution reaction in acidic condition, and its mass activity is 60 times greater than that of commercial RuO₂ at an overpotential of 300 mV. Furthermore, the RuO₂-NS/CF anode produces 2.827 A cm⁻² at a voltage of 1.7 V_cell during a single cell test, which considerably exceeds other reported catalysts. This work illustrates the significance of catalyst layer structure in electrocatalysis and sheds new light on the structural engineering of advanced catalysts.

[en] Graphical abstract: - Highlights: • Ru and Ru thermal oxides films were prepared on Ti substrate. • Material properties of OER catalytic films were monitored throughout the OER cycles. • OER activity decreased by different degradation rates for each Ru oxide film. • Anhydrous RuO_2 inhibited dissolution of Ru metal and the formation of hydrous RuO_2. - Abstract: The activity and stability of Ru metal and its thermal oxide films for the oxygen evolution reaction (OER) were investigated. The metallic Ru films were prepared by electrodeposition on a Ti substrate and then thermally oxidized at various temperatures under atmospheric conditions. During long-term operation of the OER with cyclic voltammetry (CV) in H_2SO_4 electrolyte, changes in the properties of the Ru and its thermal oxides were monitored in terms of their morphology, crystal structure, and electronic structure. In the initial stages of the OER, all of the Ru thermal oxide films underwent an activation process that was related to the continuous removal of low-activity Ru oxides from the surface. With further cycling, the OER activity decreased. The rate of decrease was different for each Ru film and was related to the annealing temperatures. Monitoring of material properties indicates that the amount of stable anhydrous RuO_2 is important for OER stability because it prevents both the severe dissolution of metallic Ru beneath the oxide surface and the formation of a less active hydrous RuO_2 at the surface.

[en] Additives having azole groups with different numbers of nitrogen atoms, such as indole, benzimidazole, indazole, benzotriazole (BTA), and 1H-benzotriazole-methanol (BTA-MeOH) were adopted to improve the mechanical hardness of electrodeposited Cu films. The effects of these additives on the film properties were elucidated in relation to their number of nitrogen atoms. Electrochemical current–potential behaviors showed that the additives containing three nitrogen atoms (BTA and BTA-MeOH) more effectively inhibited Cu electrodeposition. The inhibition strongly affected the film properties, resulting in reduced grain size and surface roughness, and increased resistivity and hardness. Cu films deposited with BTA or BTA-MeOH also exhibited 35% reduced grain size and 1.5-time higher hardness than Cu films deposited in electrolyte containing other BTA-derivatives having fewer nitrogen atoms. This notable grain refining effect of BTA and BTA-MeOH can be evaluated with respect to the strong interaction of their nitrogen atoms with the substrate and the copper ions, as well. - Highlights: • Additives of similar structure containing 1, 2, and 3 nitrogen atoms were used. • Additives with 3 nitrogen atoms more strongly inhibited Cu deposition than others. • Additives containing 3 nitrogen atoms efficiently affected film properties. • Additives having 3 nitrogen atoms remarkably improved film hardness

[en] The effect of thiourea on copper deposition onto a copper seed layer from an electrolyte composed of CuSO₄, H₂SO₄, deionized water, and thiourea was investigated. Even in the presence of very low concentrations of thiourea, extremely smooth and bright copper deposits were obtained. From the results of X-ray photoelectron spectroscopy, Auger electron spectroscopy, and electrochemical analyses, thiourea was found to react with copper or copper ions leading to the generation of CuS. CuS adsorption onto the copper seed layer seemed to inhibit the initial nucleation of the copper adions, resulting in the formation of smaller Cu grains compared to those forming in the absence of thiourea. CuS was observed to cover all active sites of the 1 cm² copper seed layer above 0.017 g/L thiourea. The surface roughness as well as the mean grain size of the deposits also approached minimum values above this thiourea concentration. Adsorbed CuS was incorporated into the deposits during electroplating, which was believed to be the major factor for the increased resistivity of the deposits

[en] As a catalyst for the hydrogen evolution reaction (HER) in alkaline water splitting, NiCo alloys of various compositions were prepared through electrodeposition onto Cu substrates. The composition of each alloy catalyst was varied by controlling the molar ratio of Co²⁺ ions in the electrolyte. With an increase in the Co content, the morphologies of the NiCo alloys were progressively changed from a round to polygonal shape. The NiCo alloys all exhibited a Ni rich surface, as confirmed by the bulk-to-surface compositional ratio and degree of alloying. The catalytic activities of the NiCo alloys toward the HER of water splitting were electrochemically tested in a KOH electrolyte, and the specific activities were characterized by considering the electrochemical surface areas of Ni and Co. The effect of alloying was demonstrated to be a significant enhancement of HER activity, resulting from a change in the electronic structures of Ni and Co.