Papers by Keyword: Water Splitting

Abstract: Hydrogen is a clean and sustainable energy source that has the potential to significantly lower carbon emissions worldwide and facilitate the switch to renewable energy sources. Meanwhile, one of the biggest obstacles to its broad use, is still sufficient hydrogen storage. This article provides a broad overview of hydrogen storage, tracing its historical development, exploring its diverse applications, examining technological advancements, addressing existing limitations, recent progress in reducing costs, and discussing the current state of the art in storage technologies, along with future directions for improvements in all forms of hydrogen storage methods. Therefore, this review highlights recent breakthroughs in hydrogen storage techniques, advances in cost reduction, and offers a step by step guide to designing next-generation functional hydrogen storage materials for improved performance, which are essential for both developed and developing hydrogen economies in cost reduction and better performance for hydrogen storage materials.

Abstract: Environmental concerns have driven the quest for clean energy solutions, with green hydrogen emerging as promising choice. This paper underscores various production methods for green hydrogen, examining their relevance and providing an overview of the utilization of Morocco's renewable energies in its production. Key challenges will be given, including water scarcity, storage, and transportation. Overall, this paper delivers a comprehensive assessment of the role of green hydrogen in Morocco’s energy transformation.

Abstract: Over the course of history, the principles of alloying have evolved, with the past fifteen years witnessing the rise of high-entropy alloying theory, which has fundamentally transformed our approach to alloy design. Developing cost-effective and efficient electrocatalysts is critical for large-scale hydrogen production via water splitting. The Ni-Co-W-Zr-P alloy coating offers a promising alternative to noble metal-based electrocatalysts. In this study, we developed a Co-W-Zr-incorporated Ni(P) coating using the electroless plating method. The integration of Co-W-Zr into the Ni(P) matrix notably enhances the number of active sites during the hydrogen evolution reaction. Electrochemical studies revealed a low overpotential of 413.5 mV of the coating when the current density is at −10 mA cm⁻². Kinetic parameters were analyzed using EIS measurements, and a potential mechanism for the hydrogen evolution reaction (HER) was proposed. The coating demonstrated exceptional stability, with no surface degradation even after prolonged electrochemical testing, making it suitable for large or irregularly shaped electrodes required in industrial applications.

Abstract: This paper introduced a low-overpotential heterostructured NiCoFe-LDH@NiCo₂O₄ electrocatalyst for hydrogen evolution reaction (HER). The hecterostructure was synthesized by the hydrothermal method. The electrocatalyst was coated on a Nikel foam (NiCoFe-LDH@NCO/NF) to make the electrodes. The synergistic effects between NiCoFe-LDH and NiCo₂O₄, coupled with the unique structure and high electrochemically active surface area, resulted in high-performance HER electrocatalytic activity. The HER performance of NiCoFe-LDH@NCO/NF electrode exhibited a low overpotential of 147 mV at a current density of 50 mAcm⁻² and a Tafel slope of 83 mVdec⁻¹. The abundance and low cost of the constituent materials make NiCoFe-LDH@NCO/NF a promising candidate for practical applications in water splitting for sustainable hydrogen production.

Abstract: This study aims to synthesize and examine the optical and photoelectrochemical properties of tungsten oxide (WO₃) nanofibers prepared by electrospinning and calcination using different temperatures (500, 700, and 900 °C). The electrospinning solution contained a mixture of polyvinyl alcohol (PVA, 7.5% w/v) and ammonium metatungstate hydrate (AMH, 16.7% w/v). The morphology of WO₃ nanofibers was observed via scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The absorbance of calcined WO₃ nanofibers was measured, and the data was used to calculate the optical band gap energy (E_g) through Tauc’s relation. The of calcined WO₃ nanofibers were found to be from 2.85 to 3.08 eV. The minimum value of was obtained from the sample calcined at 900 °C. Linear sweep voltammetry (LSV) was employed in the photocurrent measurements under simulated AM 1.5G at 100 mW/cm² irradiance. The WO₃ nanofiber photoanode calcined at 900 °C exhibited the maximum photoconversion efficiency (PCE) of 1.53%, a twice enhancement in PCE compared with those obtained from WO₃ nanofibers calcined at lower temperatures. This study suggests the potential pathway for the optimal synthesis of high performance nanostructured metal oxide electrodes for photoelectrochemical water splitting.

Abstract: Developing a photocatalysis system to generate hydrogen from water is a topic of great interest for fundamental and practical importance. In this study, hydrogen production by a new Z-scheme photocatalysis water splitting system was examined over Rh modified K₄Nb₆O₁₇ nanosheets and Pt/WO₃ photocatalysts for H₂ evolution and O₂ evolution with I^-/IO₃^- electron mediator under UV light irradiation. The H₂ evolution photocatalyst, Rh/K₄Nb₆O₁₇ nanosheets with a slit like framework, was prepared by exfoliation of and proton exchange reaction. Pt/WO₃ prepared by incipient-wetness impregnation method was used as O₂ evolution photocatalyst. The catalysts were characterized by powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy analysis (XPS), and ultraviolet-visible spectroscopy (UV-vis). These catalysts characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and ultraviolet-visible spectroscopy (UV-Vis). In this study, we developed a facile method of preparing K₄Nb₆O₁₇ nanosheets containing Rh nanoparticles. Our results show that I^- concentration and pH of reaction solution significantly influenced the photocatalytic activity. The combination of Rh modified K₄Nb₆O₁₇ nanosheets with Pt/WO₃ achieves a very high photoactivity (H₂: 4240 O₂: 1622 (μmol g^-1 h^-1)).

Abstract: Heterogeneous semiconductor based photocatalytic hydrogen (H₂) production by water splitting is one of the widely recognized promising sustainable technologies to deliver clean energy for future energy demands. The present review article mainly focus on the overview of principle of water splitting, different semiconductor nanomaterials used for photocatalytic water splitting in the presence of UV and solar light irradiation, role of sacrificial reagents, simultaneous degradation of pollutants and H₂ production reaction, strategy for development of efficient photocatalyst for H₂ production. Further the flaws associated with present photocatalytic system like recombination rate of electron–hole pairs, low visible-light response, use of hazardous irradiation sources and surface area of photocatalyst etc. has also been discussed. Recently the use of energy efficient light emitting diodes (LEDs) as an irradiation source for H₂ production is highly attracted due to its unique characteristics. Recent literature on LED source based photocatalytic system for H₂ production has also been summarized and highlighted. At last, the future prospects and challenges towards the designing of better photocatalytic system for H₂ production have also been discussed. From the literature survey, it is concluded that construction of efficient photocatalytic system for simultaneous degradation of pollutants and H₂ production under energy efficient irradiation source offer clean and simple system for solving the futuristic environmental concerns and energy crisis.

Abstract: Nowadays, hydrogen production using solar-driven photoelectrochemical (PEC) water splitting has attracted considerable attention since the introduction of TiO₂ photoelectrodes. However, TiO₂ is not able to split water on its own because the cleavage requires more than 1.4 V or even up to 1.9 V, including the redox potential of water (1.23 V) and unavoidable over-potentials. Many semiconductors have been studied, but only a very few large band gap materials can generate enough photo-voltage to cleave water for a single photoelectrode PEC water splitting cell especially processing under solar illumination. In the present study, development of WO₃-loaded TiO₂ nanotubes (WTNT) is a possible solution to generate a voltage that is high enough to split the water while absorbing more light (photons) from a greater part of solar spectrum. Furthermore, WTNT offered several advantages over the pure TiO₂ photoelectrode, such as excellent chemical and thermal stability, active at room temperature as well as responsive to UV and visible illumination. The paper concludes by presenting the comparison results between unmodified TiO₂ and WTNT photoelectrode in term of morphology, phase, elemental analysis, electrical properties, and electrochemical properties for the tandem solar-driven water splitting cell.

Abstract: The main aim of this study was to investigate size-dependent effect on the photoelectrochemical properties of nanostructured tungsten trioxide (WO₃) thin films synthesized via electrochemical method. Firstly, the nanostructured WO₃ thin films of different crystalline sizes were synthesized on fluorine-doped tin oxide (FTO) glass working electrodes followed by controlled annealing treatment at temperature of 100-600°C. The resultant nanostructured WO₃ thin films were further characterized using field emission-scanning electron microscopy (FE-SEM) and photocurrent density measurements. Through FE-SEM analysis, it was found that the WO₃ crystalline size increases with increasing annealing temperature that resulted in elevated photocurrent per unit area of the synthesized nanostructured WO₃ thin films. Finally, it was observed that the highest photocurrent density of up to 35μA/cm² was attained for WO₃ crystallines size of 86nm that formed at the annealing temperature of 600°C.

Abstract: A novel surfactant-assisted synthesis method was developed in our laboratory to enhance the oxygen storage capacity (OSC) and the thermo stability of a TWC catalyst based on zirconia and rare earth oxides. The same procedure was used to prepare ceria-zirconia compositions with different amount of ceria, either undoped or doped with La and Nd. The potential use of these materials in a two steps solar thermochemical water splitting cycle for the production of H₂ was investigated. For this proposal the O₂ release of the materials was measured through thermogravimetric analysis in N₂ at 1573K. Then all prepared compositions were subjected to an aging treatment at temperature above 1573K in air or in N₂ flow and their activity in producing H₂ via water splitting at 1073K was evaluated with respect their structural evolution. The results obtained highlight that the reactivity depends on the temperature and atmosphere of the treatments and on the composition. The best result was obtained for the ceria rich composition treated at 1573K in N₂ and for the corresponding doped composition treated in air.