Hydrogen evolution reaction on NiRE (RE=rare earth) crystalline alloys

Cerium substitution in LaCoO3 perovskite oxide as bifunctional electrocatalysts for hydrogen and oxygen evolution reactions

Perovskite oxides have attracted great attention in electrochemistry due to their compositional and structural flexibility. Herein, microwave/ultrasound assisted hydrothermal procedures were developed to synthesize Ce-doped LaCoO₃ perovskite oxide as bifunctional electrocatalysts for OER and HER application, achieving highly efficient bifunctional catalytic performance. The obtained LCC4 exhibited excellent electrocatalytic activity with an overpotential of 380 mV and 305 mV at 10 mA cm^-2 toward OER and HER, respectively. The lower Tafel slopes of 80 mV per decade and 144 mV per decade for OER and HER, respectively, indicated the faster reaction kinetics for the improved inherent electrocatalytic activity. The outstanding long-term durability of LCC4 in alkaline conditions was also vital to the practical applications of water electrolysis. The improved bifunctional electrocatalytic activity was attributed to the synergistic effects of excellent conductivity and enriched active sites arising from A-site substitution. This work not only provides an efficient strategy for the development of perovskite oxide-based electrocatalysts but also puts forward a new insight on bifunctional electrocatalysts for overall water splitting.

Rare-Earth Incorporated Alloy Catalysts: Synthesis, Properties, and Applications

To improve the performance of metallic catalysts, alloying provides an efficient methodology to design state-of-the-art materials. As emerging functional materials, rare-earth metal compounds can integrate the unique orbital structure and catalytic behavior of rare earth elements into metallic materials. Such rare-earth containing alloy catalysts proffer an opportunity to tailor electronic properties, tune charged carrier transport, and synergize surface reactivity, which are expected to significantly improve the performance and stability of catalysis. Despite its significance, there are only few reviews on rare earth containing alloys or related topics. This review summarizes the composition, synthesis, and applications of rare earth containing alloys in the field of catalysis. Subsequent to comprehensively summarizing and constructively discussing the existing work, the challenges and possibilities of future research on rare-earth metal compound materials are evaluated.

Electrochemical performance of porous Ni-alloy electrodes for hydrogen evolution reaction from seawater electrolysis

The hydrogen evolution reaction in seawater is investigated using porous Ni–Cr–Fe, Ni–Fe–Mo, Ni–Fe–C and Ni–Ti electrodes, prepared by elemental powder reactive synthesis methods. The open porosity of the four kinds of electrode materials is 23.05%, 20.47%, 25.27%, and 29.05%, respectively. The electrochemical performance of the four kinds of electrodes has been researched by polarization measurement, cyclic voltammetry and electrochemical impedance spectroscopy. The preliminary results demonstrate that the porous Ni–Cr–Fe electrode has superior catalytic activity and relatively good long-term stability for hydrogen evolution reaction in seawater. The high efficiency and reasonable stability of the porous Ni–Cr–Fe electrode catalyst demonstrate its promising applications in the rising hydrogen revolution.

The hydrogen evolution reaction in seawater is investigated using porous Ni–Cr–Fe, Ni–Fe–Mo, Ni–Fe–C and Ni–Ti electrodes, prepared by elemental powder reactive synthesis methods.

Electrodeposition of lanthanides from ionic liquids and deep eutectic solvents

Lanthanides belong to the most important raw materials and are highly demanded in high-tech industry. Low-temperature electrochemical deposition of lanthanides and lanthanide-based alloys for recycling and obtaining functional materials can provide a real alternative to the currently used high-temperature electrolysis of molten salts. The review summarizes the advancements in the field of electrodeposition of lanthanides from organic ionic systems, such as ionic liquids and deep eutectic solvents. The growing interest in these ionic systems is due to their excellent physicochemical properties, in particular non-volatility, thermal and electrochemical stability. The review also discusses further prospects and potential of the electrochemical approach for obtaining lanthanide-containing advanced materials.

The bibliography includes 219 references.

Molybdenum Nitride Electrocatalysts for Hydrogen Evolution More Efficient than Platinum/Carbon: Mo2N/CeO2@Nickel Foam

To produce hydrogen economically by electrolysis of water, one needs to develop a non-precious-metal catalyst that is as efficient as platinum metal. Here, we prepare such a catalyst by growing a layer of Mo₂N over a layer of CeO₂ deposited on nickel foam (NF) [hereafter, Mo₂N /CeO₂@NF] and show that the activity of this self-supported catalyst for hydrogen evolution in 1.0 M KOH is more efficient than that of the Pt/C electrode, achieving a current density of 10 mA/cm² at a fairly low overpotential of 26 mV. Furthermore, after a long-time electrochemical stability test for 24 h at a fixed current density, the overpotential needed to attain a current density of 10 mA/cm² is increased only by 6 mV, implying the huge potential of this method to prepare a super HER activity electrode for water splitting.

Ce-doped CoP nanoparticles embedded in carbon nanotubes as an efficient and durable catalyst for hydrogen evolution

In this work, a cerium doped CoP nanoparticles (NPs) embedded in carbon nanotubes (CNTs) for efficient and durable hydrogen evolution was developed. The detailed preparation process was described as the followings. First, cerium was introduced into ZIF-67 to form Ce-doped ZIF-67 by a joint nucleation method. Then, the Ce-doped Co-CNTs was synthesized by carbonization of Ce-doped ZIF-67. During the process, the Co²⁺ was reduced to form Co NPs and the elegant nanostructure of CNTs was formed by the catalytic effect of Co NPs. Finally, by using Ce-doped Co-CNTs as the precursor, the target catalyst (Ce_0.05-doped CoP CNTs) was obtained through a chemical vapour deposition (CVD) process in the presence of NaH₂PO₂. Results of the transmission electron microscopy (TEM) and scanning electron microscopy (SEM) showed that the target catalyst maintained the original rhombic dodecahedron morphology of ZIF-67 and the CoP NPs were embedded in CNTs and distributed uniformly throughout the catalyst. In electrochemical measurements, the catalyst showed the best performance for HER in 0.5 M H₂SO₄ solution. The onset potential, Tafel slope, electron transfer resistance (R _ct) and double-layer capacitance (C _dl) of the target catalyst was 49 mV, 78 mV dec^-1, 19.2 Ω and 10.5 mF cm^-2, respectively. Meanwhile, the catalyst yielded a current density of 10 mA cm^-2 merely at an overpotential of 146 mV. Furthermore, it maintained 90% of the original current density in a chronoamperometry measurement and showed no obvious decay even after 2000 cycles scans in a long-term durability test.

Full water splitting by a nanoporous CeO2 nanowire array under alkaline conditions

CeO₂ nanowire array was derived from MnO₂–CeO₂/TM via an acid etching strategy, and MnO₂ acts as a pore-forming agent through selective etching with oxalic acid, it shows excellent OER and HER performance.

Vanadium doped few-layer ultrathin MoS2 nanosheets on reduced graphene oxide for high-performance hydrogen evolution reaction

In this paper, we demonstrate a facile solvothermal synthesis of a vanadium(v) doped MoS₂-rGO nanocomposites for highly efficient electrochemical hydrogen evolution reaction (HER) at room temperature. The surface morphology, crystallinity and elemental composition of the as-synthesized material have been thoroughly analyzed. Its fascinating morphology propelled us to investigate the electrochemical performance towards the HER. The results show that it exhibits excellent catalytic activity with a low onset potential of 153 mV versus reversible hydrogen electrode (RHE), a small Tafel slope of 71 mV dec⁻¹, and good stability over 1000 cycles under acidic conditions. The polarization curve after the 1000^th cycle suggests there has been a decrement of less than 5% in current density with a minor change in onset potential. The synergistic effects of V-doping at S site in MoS₂ NSs leading to multiple active sites and effective electron transport route provided by the conductive rGO contribute to the high activity for the hydrogen evolution reaction. The development of a high-performance catalyst may encourage the effective application of the as-synthesized V-doped MoS₂-rGO as a promising electrocatalyst for hydrogen production.

In this paper, we demonstrate a facile solvothermal synthesis of a vanadium(v) doped MoS₂-rGO nanocomposites for highly efficient electrochemical hydrogen evolution reaction (HER) at room temperature.

The electrochemical applications of rare earth-based nanomaterials

This review presents a general description of the synthesis and electrochemical properties of rare earth-based nanomaterials and their electrochemical applications.

Molybdenum Carbide Nanoparticles on Carbon Nanotubes and Carbon Xerogel: Low-Cost Cathodes for Hydrogen Production by Alkaline Water Electrolysis

Low-cost molybdenum carbide (Mo2 C) nanoparticles supported on carbon nanotubes (CNTs) and on carbon xerogel (CXG) were prepared and their activity for the hydrogen evolution reaction (HER) was evaluated in 8 m KOH aqueous electrolyte at 25-85 °C. Measurements of the HER by linear scan voltammetry allowed us to determine Tafel slopes of 71 and 74 mV dec(-1) at 25 °C for Mo2 C/CNT and Mo2 C/CXG, respectively. Stability tests were also performed, which showed the steady performance of the two electrocatalysts. Moreover, the HER kinetics at Mo2 C/CNT was enhanced significantly after the long-term stability tests. The specific activity of both materials was high, and a higher stability was obtained for the activated Mo2 C/CNT (40 A g(-1) at -0.40 V vs. the reversible hydrogen electrode).

Highly Efficient and Robust Nickel Phosphides as Bifunctional Electrocatalysts for Overall Water-Splitting

To search for the efficient non-noble metal based and/or earth-abundant electrocatalysts for overall water-splitting is critical to promote the clean-energy technologies for hydrogen economy. Herein, we report nickel phosphide (NixPy) catalysts with the controllable phases as the efficient bifunctional catalysts for water electrolysis. The phases of NixPy were determined by the temperatures of the solid-phase reaction between the ultrathin Ni(OH)2 plates and NaH2PO2·H2O. The NixPy with the richest Ni5P4 phase synthesized at 325 °C (NixPy-325) delivered efficient and robust catalytic performance for hydrogen evolution reaction (HER) in the electrolytes with a wide pH range. The NixPy-325 catalysts also exhibited a remarkable performance for oxygen evolution reaction (OER) in a strong alkaline electrolyte (1.0 M KOH) due to the formation of surface NiOOH species. Furthermore, the bifunctional NixPy-325 catalysts enabled a highly performed overall water-splitting with ∼100% Faradaic efficiency in 1.0 M KOH electrolyte, in which a low applied external potential of 1.57 V led to a stabilized catalytic current density of 10 mA/cm(2) over 60 h.

Hydrogen evolution on nanostructured Ni–Cu foams

Tafel plots for the two foams and their morphology observed by SEM.

Physicochemical and Electrical Properties of Praseodymium Oxides

The industrial research is continuously looking for novelties that could improve the applied processes, increasing the yields, lowering the costs, or improving the performances. In industrial electrochemistry, one more aspect is the stability of electrode materials, which is generally balanced by the catalytic activity: the higher the latter, the lower the former. A compromise has to be found, and an optimization is often the result of new ideas that completely change the way of thinking. Praseodymium-oxide-based cathodes have been proved to be quite interesting devices: the hydrogen evolution reaction is guaranteed by the presence of a noble metal (platinum and/or rhodium), while the stability and poisoning resistance seem to be strongly improved by the presence of lanthanide oxides.