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Here we report the optimization of the fabrication conditions for AuNi bimetallic catalysts supported on self-ordered titania nanotube arrays (AuNi-TiO2ntb). A series of efficient AuNi-TiO2ntb catalysts with small amounts of Au in the range of 1.74 to 15.7 μgAu·cm−2 have been fabricated by anodization, electroless Ni plating, and galvanic displacement techniques. The electrocatalytic activity of the catalysts has been evaluated for BH4− ion oxidation in an alkaline medium using cyclic voltammetry and chronoamperometry. The performance of a NaBH4-H2O2 fuel cell with Ni-TiO2ntb and AuNi-TiO2ntb anode catalysts has been investigated at different temperatures. It was found that the electrocatalytic activity of AuNi-TiO2ntbs catalysts was improved remarkably when the Ni layer of 100 and 400 nm was used for the deposition of Au crystallites. The Ni-TiO2ntb catalyst generates the maximum power density values of ca. 85–121 mW·cm−2 at a temperature of 25–55 °C, whereas the AuNi-TiO2ntb catalysts that have the Au loading of 3.07 and 15.7 μgAu·cm−2 achieve the power density values of ca. 104–147 and 119–170 mW·cm−2, respectively, at a temperature of 25–55 °C.

In this study, sodium borohydride oxidation has been investigated on the platinum nanoparticles modified copper/titanium catalysts (PtNPsCu/Ti), which were fabricated by employing the electroless copper plating and galvanic displacement technique. ICP-OES, XRD, FESEM, and EDX have been used to characterize PtNPsCu/Ti catalysts’ composition, structure, and surface morphology. The oxidation of sodium borohydride was examined on the PtNPsCu/Ti catalysts using cyclic voltammetry and chrono-techniques.

Direct hydrazine fuel cells (DHFCs) are one type of direct liquid fuel cells (DLFCs), where hydrazine is used as a fuel. DHFCs can be operated using a non-precious metal catalyst, which potentially contributes to cost reduction of the hydrazine fuel cell technology. Despite the tremendous progress made in the development of an active catalyst for DHFCs, however, available perfect catalyst able to meet the power output requirements for commercial fuel cell vehicles is still an issue. In this chapter, we summarize the recent advances in the development of catalysts for direct hydrazine fuel cells (DHFCs). The challenges and perspectives in this field are also discussed.

The electrochemical stability and durability of ZnCo alloy thin layers deposited on the titanium surface (denoted as ZnCo/Ti) and those modified by small amounts of Au nanoparticles (denoted as AuZnCo/Ti) prepared via the electrochemical metal deposition technique and a simple galvanic displacement have been investigated in alkaline sodium borohydride (NaBH4) solutions. The physical properties of the fabricated AuZnCo/Ti catalysts have been examined using field emission scanning electron microscopy (FESEM), energy dispersive X-ray analysis (EDX) and inductively coupled plasma optical emission spectroscopy (ICP-OES). The electrocatalytic activity of the ZnCo/Ti and AuZnCo/Ti catalysts toward the oxidation of NaBH4 has been evaluated in an alkaline medium using cyclic voltammetry (CV) and chronoamperometry (CA), whereas the catalytic efficiency of the catalysts for the hydrolysis reaction of NaBH4 has been also examined by measuring the amount of generated hydrogen via the classic water-displacement method. It has been determined that the modification of the ZnCo alloy coating by Au nanoparticles apparently improves not only the morphology and structure of the catalyst, but also the activity and stability of the one for the oxidation of NaBH4 in an alkaline medium as compared to those of ZnCo/Ti and bare Au. The AuZnCo/Ti catalysts that have Au loadings of 63 and 306 µg cm–2 give ca. 12 and 11, respectively, times higher NaBH4 oxidation current densities as compared to those of the bare Au catalyst. Moreover, the AuZnCo/Ti catalysts catalyze the hydrolysis reaction of NaBH4 in alkaline solutions.

This work presents the investigation of the electrochemical oxidation of hydrazine and sodium borohydride ions in alkaline solutions on the Au nanoparticles modified ZnCo coating surface, which was deposited on the titanium substrate (termed as AuZnCo/Ti). The AuZnCo/Ti catalysts were prepared via a facile electrochemical deposition technique followed by a simple and low-cost galvanic displacement. Scanning electron microscopy, energy dispersive X-ray analysis and inductively coupled plasma optical emission spectroscopy were used for characterization of the prepared catalysts surface morphology, structure and composition, whereas their electrocatalytic behaviour was investigated for the electrochemical oxidation of hydrazine and sodium borohydride in an alkaline medium using cyclic voltammetry. It has been determined that the AuZnCo/Ti catalysts with Au loadings of 31, 63 and 306 µg cm–2 show enhanced catalytic activity towards the electrochemical oxidation of both hydrazine and sodium borohydride as compared to that of the ZnCo/Ti catalyst.

In this study we report a facile approach for fabrication of flexible anode catalysts consisting of a fiber-shaped cobalt deposited on the polyimide (PI) surface for direct hydrazine fuel cells (DHFCs). At first, a thin copper layer has been deposited on the PI surface using electroless metal plating method. Then, the fiber-shaped cobalt coating has been plated by the electrochemical deposition method from the electrolyte containing CoSO4, NaOH and N-(2-Hydroxyethyl) ethylenediamine. For comparison, the cobalt layer that has the smooth structure has been deposited on the flexible PI surface via electroless deposition using morpholine borane as a reducing agent. The morphology and composition of the prepared flexible catalysts have been characterized using scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray diffraction. The activity of catalysts has been investigated with respect to the oxidation of hydrazine in an alkaline medium. The results of electrochemical measurements showed that the deposited cobalt layer that has a fiber-shaped structure on the flexible PI surface exhibits an enhanced electrocatalytic activity towards the oxidation of hydrazine as compared with that for cobalt catalyst that has a smooth structure. Moreover, the prepared flexible catalysts seem to be a promising anode material for DHFCs.

Low-temperature fuel cells operating on methanol or ethanol fuel comprise a promising class alternative sources of energy. Active search for cost-effective and efficient catalysts is still in progress. In this study, the oxidation of methanol and ethanol has been investigated on the needle-shaped cobalt (Coneedle) catalyst decorated with low amounts of platinum nanoparticles (PtNPs). The electrochemical and chemical methods were used for the fabrication of the PtNPs decorated needle-shaped Co catalysts. The electrocatalytic activity of the as-prepared PtNPs-Coneedle catalysts for the oxidation of methanol and ethanol in an alkaline media was evaluated using cyclic voltammetry and chrono-techniques. The data on methanol and ethanol oxidation under different conditions will be presented and discussed. It has been determined that the decoration of the needle-shaped cobalt catalyst with low amounts of Pt nanoparticles results in enhanced electrocatalytic activity for methanol and ethanol oxidation, compared with that of pure needle-shaped Co and seem to be a promising anode material for direct methanol and ethanol fuel cells.

In the present study, the commercially available CVD graphene-Ni/SiO2/Si (Graphene-Supermarket) template was used as a substrate for the deposition of gold nanoparticles (AuNPs). The immersion of the CVD graphene into the 1 mM HAuCl4 solution at a temperature of 25 oC for 1 min results in the deposition of AuNPs on the surface of the CVD graphene-Ni/SiO2/Si. The surface morphology and structure as well as composition of the prepared catalysts were characterized by Scanning Electron Microscopy (SEM) and Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES). The electrocatalytic activity of the AuNPs modified CVD graphene-Ni/SiO2/Si catalyst was evaluated for the oxidation of sodium borohydride and hydrazine using cyclic voltammetry and chrono-techniques. It was found that the CVD graphene-Ni/SiO2/Si modified with AuNPs exhibits a significantly higher electrocatalytic efficiency for sodium borohydride and hydrazine oxidation as compared with that of pure CVD graphene-Ni/SiO2/Si electrode, and seems to be a promising anode material for direct borohydride and hydrazine fuel cells.

In this study, the electro-oxidation of hydrazine in an alkaline medium was investigated on the zinc-cobalt (ZnCo) coating, which was deposited on the titanium (Ti) surface and then modified with low amounts of gold nanoparticles (AuNPs). The AuNPs-ZnCo/Ti catalysts with different amount of AuNPs were prepared via a facile electrochemical deposition technique followed by a simple and low-cost galvanic displacement. Field Emission Scanning Electron Microscopy, Energy Dispersive X-ray Analysis and Inductively Coupled Plasma Optical Emission Spectroscopy were used for the characterization of the surface morphology, structure and composition of the as-prepared AuNPs-ZnCo/Ti catalysts. Electrocatalytic behavior of catalysts was investigated towards the electro-oxidation of hydrazine in an alkaline medium using Cyclic Voltammetry. It was found that the AuNPs-ZnCo/Ti catalysts were prepared with the Au loadings of 31, 63 and 306 µg cm-2 after the immersion of the ZnCo/Ti catalyts into the 1 mM HAuCl4 solution for 0.5, 1 and 5 min, respectively. Moreover, the ZnCo/Ti catalysts modified by AuNPs has significantly higher catalytic activity towards the electro-oxidation of hydrazine as compared to that of the ZnCo/Ti catalyst. Additionaly, modification of the ZnCo/Ti catalyst by AuNPs leads to the rather pronounced shift in hydrazine oxidation potential to more negative potential region and is followed by a substantial increase in direct hydrazine oxidation rate as compared to that of the unmodified ZnCo/Ti catalyst.

In the present work, the smooth and fiber-shaped Co coatings decorated with Pt crystallites were investigated as the anode material in direct borohydride-hydrogen peroxide fuel cells (DBHPFCs). The Co sublayers, which have different structures, e.g. smooth and fiber-shaped, were used as a substrate for the depositing of Pt crystallites. The Co layer having smooth structure was deposited on the Cu surface (denoted as Cosmooth/Cu) via electroless deposition using morpholine borane as a reducing agent. Co layers, which have a fiber-shaped structure and the thickness of ~3 mm, were electroplated on the Cu surface (denoted as Cofiber/Cu) from the electrolyte containing CoSO4, NaOH and N-(2-Hydroxyethyl) ethylenediamine. The Pt crystallites were deposited on the Cosmooth/Cu and Cofiber/Cu electrodes by their immersion into a Pt(IV)-containing solution at a temperature of 25oC for different time periods. It has been determined that the Pt loadings were in the range from 10 to 14 µgPt cm–2 and 5 to 29 µgPt cm–2 in the PtCosmooth/Cu and PtCofiber/Cu catalysts, respectively. The activity of the prepared PtCosmooth/Cu and PtCofiber/Cu catalysts for borohydride oxidation reaction (BOR) was evaluated using cyclic voltammetry and chronoamperometry. The performance of a DBHPFC operating with 1 M NaBH4 + 4 M NaOH as fuel and 5 M H2O2 + 1.5 M HCl as an oxidant, while employing Pt as the cathode catalyst and PtCosmooth/Cu and PtCofiber/Cu catalysts with different Pt loadings as the anodes were investigated. It has been determined that the prepаred PtCosmooth/Cu and PtCofiber/Cu cаtаlysts hаve а higher аctivity аnd а better stаbility for the oxidаtion of BH4 - compаred to those of Cosmooth/Cu аnd Cofiber/Cu. The аssembled direct borohydride-hydrogen peroxide fuel cell with PtCosmooth/Cu and PtCofiber/Cu cаtаlysts as the anodes exhibited аn open circuit voltаge of cа. 1.9 V. Acknowledgment This research was funded by a grant (No. M-ERA.NET-1/2016) from the Research Council of Lithuania.