Hydrogen

3 pages, 166 KiB

Open AccessEditorial

Welcome to Hydrogen—A New International and Interdisciplinary Open Access Journal of Growing Interest in Our Society

by George E. Marnellos and Thomas Klassen

Hydrogen 2020, 1(1), 90-92; https://doi.org/10.3390/hydrogen1010006 - 22 Dec 2020

Cited by 4 | Viewed by 2953

Abstract

The 2018 Intergovernmental Panel on Climate Change (IPCC) report [...] Full article

26 pages, 6915 KiB

Open AccessArticle

Role of the Sulphur Source in the Solvothermal Synthesis of Ag-CdS Photocatalysts: Effects on the Structure and Photoactivity for Hydrogen Production

by Erika Soto Morillo, Noelia Mota Toledo, Jose Luisa García Fierro and Rufino M. Navarro Yerga

Hydrogen 2020, 1(1), 64-89; https://doi.org/10.3390/hydrogen1010005 - 19 Dec 2020

Cited by 6 | Viewed by 3143

Abstract

The aim of this work is to study the influence of the sulphur source (elemental sulphur, thiourea and L-cysteine) in the solvothermal synthesis of Ag-CdS over its growth, structuration and state of Ag and how these changes influence on its photoactivity. The differences in the generation rate of the S²⁻ from the sulphur sources during the solvothermal synthesis determine the nucleation and growth pathways of CdS affecting to the silver state and its incorporation into the CdS lattice. The hydrogen production on Ag-CdS photocatalysts decreases according the sequence: thiourea > elemental sulphur >> L-cysteine. The changes in the photoactivity of Ag-CdS samples are analysed in terms of the differences in the insertion of Ag⁺ into the CdS lattice, the formation of composites between CdS and Ag₂S and the formation of CdS crystalline domains with strong confinement effect derived from the different sulphur source used in the solvothermal synthesis. Full article

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26 pages, 2981 KiB

Open AccessReview

Enhancing the Hydrogen Storage Properties of A_xB_y Intermetallic Compounds by Partial Substitution: A Short Review

by Andrii Lys, Julien O. Fadonougbo, Mohammad Faisal, Jin-Yoo Suh, Young-Su Lee, Jae-Hyeok Shim, Jihye Park and Young Whan Cho

Hydrogen 2020, 1(1), 38-63; https://doi.org/10.3390/hydrogen1010004 - 15 Dec 2020

Cited by 45 | Viewed by 9077

Abstract

Solid-state hydrogen storage covers a broad range of materials praised for their gravimetric, volumetric and kinetic properties, as well as for the safety they confer compared to gaseous or liquid hydrogen storage methods. Among them, A_xB_y intermetallics show outstanding performances, notably for stationary storage applications. Elemental substitution, whether on the A or B site of these alloys, allows the effective tailoring of key properties such as gravimetric density, equilibrium pressure, hysteresis and cyclic stability for instance. In this review, we present a brief overview of partial substitution in several A_xB_y alloys, from the long-established AB₅ and AB₂-types, to the recently attractive and extensively studied AB and AB₃ alloys, including the largely documented solid-solution alloy systems. We not only present classical and pioneering investigations, but also report recent developments for each A_xB_y category. Special care is brought to the influence of composition engineering on desorption equilibrium pressure and hydrogen storage capacity. A simple overview of the A_xB_y operating conditions is provided, hence giving a sense of the range of possible applications, whether for low- or high-pressure systems. Full article

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16 pages, 3516 KiB

Open AccessArticle

Controllable H₂ Generation by Formic Acid Decomposition on a Novel Pd/Templated Carbon Catalyst

by Maria Mihet, Monica Dan, Lucian Barbu-Tudoran, Mihaela D. Lazar and Gabriela Blanita

Hydrogen 2020, 1(1), 22-37; https://doi.org/10.3390/hydrogen1010003 - 12 Nov 2020

Cited by 13 | Viewed by 3193

Abstract

A novel Pd/templated carbon catalyst (Pd/TC) was developed, characterized, and tested in the dehydrogenation of formic acid (FA) under mild conditions, with the possibility to control the H₂ generation rate, in the absence or presence of HCOONa (SF), by adjusting the Pd:FA and/or FA:SF ratios. The characterization results of the templated carbon obtained by the chemical vapor deposition of acetylene on NaY zeolite revealed different structural and morphological properties compared to other C-based supports. Therefore, it was expected to induce a different catalytic behavior for the Pd/TC catalyst. Indeed, the TC-supported Pd catalyst exhibited superior activity in the decomposition of FA, even at room temperature, with turnover frequencies (TOFs) of up to 143.7 and 218.8 h⁻¹ at 60 °C. The H₂ generation rate increased with an increasing temperature, while the H₂ yield increased with a decreasing FA concentration. Constant generation of gaseous flow (H₂ + CO₂) was achieved for 11 days, by the complete dehydrogenation of FA at room temperature using a 2 M FA solution and Pd:FA = 1:2100. The presence of SF in the reaction medium significantly enhanced the H₂ generation rate (535 h⁻¹ for FA:SF = 3:1 and 60 °C). Full article

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11 pages, 1364 KiB

Open AccessArticle

The Synergistic Effects of Alloying on the Performance and Stability of Co₃Mo and Co₇Mo₆ for the Electrocatalytic Hydrogen Evolution Reaction

by Youyi Sun and Alexey Y. Ganin

Hydrogen 2020, 1(1), 11-21; https://doi.org/10.3390/hydrogen1010002 - 10 Oct 2020

Cited by 6 | Viewed by 4111

Abstract

Metal alloys have become a ubiquitous choice as catalysts for electrochemical hydrogen evolution in alkaline media. However, scarce and expensive Pt remains the key electrocatalyst in acidic electrolytes, making the search for earth-abundant and cheaper alternatives important. Herein, we present a facile and efficient synthetic route towards polycrystalline Co₃Mo and Co₇Mo₆ alloys. The single-phased nature of the alloys is confirmed by X-ray diffraction and electron microscopy. When electrochemically tested, they achieve competitively low overpotentials of 115 mV (Co₃Mo) and 160 mV (Co₇Mo₆) at 10 mA cm⁻² in 0.5 M H₂SO₄, and 120 mV (Co₃Mo) and 160 mV (Co₇Mo₆) at 10 mA cm⁻² in 1 M KOH. Both alloys outperform Co and Mo metals, which showed significantly higher overpotentials and lower current densities when tested under identical conditions, confirming the synergistic effect of the alloying. However, the low overpotential in Co₃Mo comes at the price of stability. It rapidly becomes inactive when tested under applied potential bias. On the other hand, Co₇Mo₆ retains the current density over time without evidence of current decay. The findings demonstrate that even in free-standing form and without nanostructuring, polycrystalline bimetallic electrocatalysts could challenge the dominance of Pt in acidic media if ways for improving their stability were found. Full article

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10 pages, 1039 KiB

Open AccessArticle

Water Removal from LOHC Systems

by Karsten Müller, Rabya Aslam, André Fikrt, Christoph Krieger and Wolfgang Arlt

Hydrogen 2020, 1(1), 1-10; https://doi.org/10.3390/hydrogen1010001 - 10 Oct 2020

Cited by 1 | Viewed by 3440

Abstract

Liquid organic hydrogen carriers (LOHC) store hydrogen by reversible hydrogenation of a carrier material. Water can enter the system via wet hydrogen coming from electrolysis as well as via moisture on the catalyst. Removing this water is important for reliable operation of the LOHC system. Different approaches for doing this have been evaluated on three stages of the process. Drying of the hydrogen, before entering the LOHC system itself, is preferable. A membrane drying process turns out to be the most efficient way. If the water content in the LOHC system is still so high that liquid–liquid demixing occurs, it is crucial for water removal to enhance the slow settling. Introduction of an appropriate packing can help to separate the two phases as long as the volume flow is not too high. Further drying below the rather low solubility limit is challenging. Introduction of zeolites into the system is a possible option. Water adsorbs on the surface of the zeolite and moisture content is therefore decreased. Full article

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Hydrogen, Volume 1, Issue 1 (December 2020) – 6 articles

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