Water Splitting For Hydrogen Production Research Articles

First Principles Study of Photocatalytic Water Splitting Hydrogen Production by SiI2 Nanotubes

First Principles Study of Photocatalytic Water Splitting Hydrogen Production by SiI2 Nanotubes

NiMo/NiFe-LDH heterostructured electrocatalyst for hydrogen production from water electrolysis

Constructing low-cost and efficient catalysts for electrocatalytic water splitting to produce hydrogen is of great significance. In this study, we successfully prepared NiMo/NiFe-LDH electrocatalysts with abundant coupled interfaces using a hydrothermal method and electrodeposition. The synergistic effect between the NiMo alloy and NiFe-LDH nanosheets induces charge redistribution at the interface and accelerates charge transfer, thus improving reaction kinetics and enhancing electrocatalytic performance. Experimental results show that at a current density of 10 mA cm−2, the HER overpotential of NiMo/NiFe-LDH is 35 mV, demonstrating excellent water-splitting performance. This work provides insights into the development of alloy/transition metal hydroxides for efficient water-splitting hydrogen production

Selection of Solar-Based Water-Splitting Hydrogen Production and Hydrogen Storage Technologies Using Neutrosophic Analytic Hierarchy Process and Neutrosophic Complex Proportional Assessment

Abstract The production of hydrogen through water-splitting using solar energy has the potential to meet the world’s future energy demand while also addressing the issue of greenhouse gas emissions. To compare and select the best technology among solar thermochemical cycles, photoelectrochemical, and photocatalytic water-splitting in terms of solar-to-hydrogen efficiency, production cost, safety, life expectancy, maintenance cost, and detrimental impact on the environment, this study used a multi-criteria decision analysis hybrid called Neutrosophic Analytic Hierarchy Process (NAHP) and Neutrosophic Complex Proportional Assessment (NCOPRAS). The same method was used to determine the best technology for automobiles among compressed hydrogen storage, metal hydrides, metal-organic frameworks, and chemical storage in terms of gravimetric system capacity, volumetric system capacity, safety, system cost, cycle life, energy efficiency, detrimental impact on the environment, and refueling time. There were 4 experts each in hydrogen storage and hydrogen, specifically from the Philippines, Australia, India, Romania, and Italy. All experts’ judgments have a consistency ratio (CR) < 0.1. The priority criterion for hydrogen production was life expectancy (weighted value (WV) = 0.189), and gravimetric system capacity for hydrogen storage (WV = 0.137). The result showed that among all alternatives for hydrogen production, the solar thermochemical cycle was the best (relative significance value (RSV) = 0.3432) as for hydrogen storage, the best technology among the alternatives was metal hydrides (RSV = 0.2575). A sensitivity analysis was used to check the variability and robustness of the solution.

Pristine and Nature‐Inspired Hematite (α‐Fe2O3) Nanoparticles and Search for their Photocatalytic Application

AbstractThe article describes synthesis of green‐mediated hematite nanoparticles (20–30 nm) using Polianthes tuberosa flower extract. Structural, microscopic, and magnetic studies confirm the synthesis of iron oxide nanoparticles of pure hematite phase. Spectroscopic techniques are employed to identify different electronic transitions and defect levels as well as to estimate the energy bandgap and Urbach energy. A correlation among the particle size, bandgap energy, and Urbach energy is noticed. These hematite nanoparticles act as visible light photocatalyst which degrade dye in aqueous medium without the addition of any additives. The catalyst particle size, catalyst quantity, pH of dye solution, and solution temperature have significant impact on the photodegradation process of dye molecules in aq. solution. All observations advocate that green synthesis of hematite nanoparticles with Polianthes tuberosa flower extract can significantly modulate their optical and photocatalytic properties. These materials may find potential uses in water splitting for hydrogen production and purification of water by removing organic pollutants. The study highlights that using commercially cheap starting materials and extract made from naturally available plant parts, materials having huge application potentials can be synthesized at low cost by the simple green synthesis approach.

Tailoring Ni-Fe-B Electronic Effects in Layered Double Hydroxides for Enhanced Oxygen Evolution Activity.

NiFe layered double hydroxides (LDHs) are state-of-the-art catalysts for the oxygen evolution reaction (OER) in alkaline media, yet they still face significant overpotentials. Here, quantitative boron (B) doping is introduced in NiFe LDHs (ranging from 0% to 20.3%) to effectively tailor the Ni-Fe-B electronic interactions for enhanced OER performance. The co-hydrolysis synthesis approach synchronizes the hydrolysis rates of Ni and Fe precursors with the formation rate of B─O─M (M: Ni, Fe) bonds, ensuring precise B doping into the NiFe LDHs. It is demonstrated that B, as an electron-deficient element, acts as an "electron sink" at doping levels from 0% to 13.5%, facilitating the transition of Ni2+ to the active Ni3+δ, thereby accelerating OER kinetics. However, excessive B doping (13.5-20.3%) effectively generates oxygen vacancies in the LDHs, which increases electron density at Ni2+ sites and hinders their transition to Ni3+δ, thereby reducing OER activity. Optimal OER performance is achieved at a B doping level of 13.5%, with an overpotential of only 208mV to reach a current density of 500mA cm-2, placing it among the most effective OER catalysts to date. This Ni-Fe-B electronic engineering opens new avenues for developing highly efficient anode catalysts for water-splitting hydrogen production.

Photocatalytic overall water splitting Z-schemes for hydrogen production with the X@CTF-0/β-Sb (X = S, Se) heterostructures

The covalent triazine framework (CTF-0) is believed to possess the potential to serve as a photocatalyst for overall water splitting, but its large bandgap constrains the solar-to-hydrogen (STH) efficiency. Here, we demonstrate that the STH efficiency can be boosted by constructing the CTF-0/β-Sb heterostructure and manipulating the band gap by the doped S or Se atoms in the CTF-0 monolayer. The electronic, optical, and thermodynamic properties are calculated to justify the photocatalytic Z-scheme for overall water splitting, and the interlayer transfers of the photogenerated carriers are investigated using non-adiabatic molecular dynamics simulations to understand the photocatalytic activity of the carriers. The electronic properties indicate that the band alignments hold a staggered character and there is a built-in electric field from the β-Sb to the CTF-0 monolayers in the heterostructures, which supports the photogenerated carriers to perform photocatalytic overall water splitting with Z-scheme and STH efficiencies of 13.28 % and 12.17 % can be achieved for the S@CTF-0/β-Sb and Se@CTF-0/β-Sb heterostructures. Moreover, the STH efficiencies remain increasing within 4 % biaxial strains, regardless of the tensile and compressive ones, implying that no need to worry about the effect of the smaller deformations on the photocatalytic performance in the preparation. Nonadiabatic molecular dynamics simulations show that the photocatalytic activities of the photogenerated carriers in the S@CTF-0/β-Sb are better protected in comparison with those in the Se@CTF-0/β-Sb heterostructures. However, the recombination times indicate that the latter can exert a better photocatalytic performance. Therefore, both the S@CTF-0/β-Sb and Se@CTF-0/β-Sb heterostructures are promising candidates for overall water-splitting for hydrogen production.

Polyaniline as a solid-state charge conductor for enhanced photocatalytic hydrogen production and value-added disulfide synthesis

Efficient transfer and maximal utilization of photogenerated electrons and holes in photocatalytic processes, along with the simultaneous production of hydrogen and high-value chemicals, represent a promising approach for effective solar energy utilization. Herein, polyaniline (PANI) was employed as a charge conductor to enhance the heterojunction structure between g-C3N4 and CdS, thereby facilitating the efficient interfacial transfer of photogenerated carriers. The obtained composite has demonstrated outstanding photocatalytic performance in both water splitting for hydrogen production and the dehydrogenation coupling of thiols. The hydrogen evolution efficiency of g-C3N4-PANI-CdS composite in water splitting is 41.67 times higher than that of the original g-C3N4. Additionally, the sample exhibits efficient splitting and re-polymerization capabilities for 4-methoxythiophenol (4-MTP), achieving the efficient hydrogen production and bis (4-methoxyphenyl) disulfide (4-MPD) synthesis concurrently. Comprehensive characterization methods confirm that PANI acts as a highly conductive layer, accelerating rapid charge transfer and separation at the interface between g-C3N4 and CdS, significantly improving the utilization of surface active sites. This study provides valuable insights for the future advancements in photocatalytic hydrogen generation and disulfides synthesis.

Developing an online composition prediction for an HI–I2–H2O system using deep neural network

We developed a deep neural network (DNN) method to predict the composition of the HI–I2–H2O system in the iodine–sulfur (IS) process of thermochemical water-splitting hydrogen production using measurable properties. Unlike conventional titration analysis, this approach allows for a quick understanding of fluid composition, providing essential information for controlling operating conditions. This study focused on the HI–I2–H2O three-component system within the IS process. Gibbs’ phase rule was used to construct the DNN model using online measurement parameters, such as temperature, pressure, and density, as input conditions. The model was trained with experimental data, and the structural parameters were tuned. Composition prediction using actual trend data correlated well with titration analysis measurements. The local interpretable model-agnostic explanations method was incorporated to acquire insights into the significance of input parameters for compositions from the DNN model, providing valuable information on crucial parameters for effective composition control.

Ag-doped SrTiO3: Enhanced water splitting for hydrogen production

This study investigates the effect of Ag-doping on the (001) surface of SrTiO3 (STO) to enhance hydrogen production via water-splitting employing density functional theory (DFT) simulations. It was found that the heterolytic water dissociation on Ag-doped (001)-STO occurs via a first-order reaction with an energy barrier of 5.74 kJ/mol, representing a reduction of 94% compared to undoped (001)-STO. The Gibbs free energy of H2 formation catalyzed by Ag-doped (001)-STO is approximately −302 kJ/mol, indicating the spontaneity of this process. Additionally, the surface band gap energy decreases by ∼2 eV after water-splitting, suggesting charge transfer from the Ag-doped STO to the water and leading to new electron-hole recombination states. This research underscores the potential of Ag-doping in enhancing the efficiency of hydrogen production through water-splitting, contributing to the development of greener and more efficient energy technologies.

Electronic Structure Modification of MnO2 Nanosheet Arrays with Enhanced Water Oxidation Activity and Stability by Nitrogen Plasma.

The strategic design of catalysts for the oxygen evolution reaction (OER) is crucial in tackling the substantial energy demands associated with hydrogen production in electrolytic water splitting. Despite extensive research on birnessite (δ-MnO2) manganese oxides to enhance catalytic activity by modulating Mn3+ species, the ongoing challenge is to simultaneously stabilize Mn3+ while improving overall activity. Herein, oxygen (O) vacancies and nitrogen (N) doping have been simultaneously introduced into the MnO2 through a simple nitrogen plasma approach, resulting in efficient OER performance. The optimized N-MnO2v electrocatalyst exhibits outstanding OER activity in alkaline electrolyte, reducing the overpotential by nearly 160 mV compared to pure pristine MnO2 (from 476 to 312 mV) at 10 mA cm-2, and a small Tafel slope of 89 mV dec-1. Moreover, it demonstrates excellent durability over a 122 h stability test. The introduction of O vacancies and incorporation of N not only fine-tune the electronic structure of MnO2, increasing the Mn3+ content to enhance overall activity, but also play a crucial role in stabilizing Mn3+, thereby leading to exceptional stability over time. Subsequently, density functional theory calculations validate the optimized electronic structure of MnO2 achieved through the two engineering methods, effectively lowering the intermediate adsorption free energy barrier. Our synergistic approach, utilizing nitrogen plasma treatment, opens a pathway to concurrently enhance the activity and stability of OER electrocatalysts, applicable not only to Mn-based but also to other transition metal oxides.

Radiation-catalytic activity of zirconium surface during water splitting for hydrogen production

Zirconium was treated with different doses (10–400 kGy) of radiation; leading to the surface oxide formation. High doses of radiation (D ≥ 120 kGy) led formation of a stable protective surface oxide phase with low water splitting ability. However, higher doses (D ≥ 400 kGy) led to catastrophic oxidation of zirconium. In the thermal process, the values of G (H2) and W(H2) for ZrO2 were 1.18 molecules/100 eV and 2.24 molecules/g. These values for ZrZrO2 were 2.22 molecules/100 eV and 2.36 molecules/g. In the radiation-thermal process, the values of G (H2) and W(H2) for ZrO2 were 2.30 molecules/100 eV and 4.42 molecules/g. These values for ZrZrO2 were 5.58 molecules/100 eV and 4.95 molecules/g. It was observed that hydrogen production was greater in the radiation-thermal process than in the thermal process only. Similarly, the hydrogen production was greater with ZrZrO2 in comparison to ZrO2. The present research is useful in nuclear reactors with zirconium having oxide layers and as a future hydrogen production method by water splitting.

Vertically aligned ReS2 on MOF deorived CoS2–C hybrid as core-shell catalyst for promoting overall water splitting

The rational design of a core-shell structured electrocatalyst is important to improve the efficiency of electrocatalytic hydrogen production through water splitting. Herein, the catalyst is composed of rhenium disulfides (ReS2) vertically grown on cobalt sulfides/carbon hybrid by hydrothermal and activation treatment (CoS2–C@ReS2/CFP). The core-shell structure is constructed by sulfurizing the cobalt-based metal-organic framework, preventing the restacking of the ReS2 nanosheet, exposing more active sites, and facilitate electrolyte ion diffusion. Moreover, the CoS2–C@ReS2/CFP catalyst shows exceptional performance during the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) process in an alkaline electrolyte. At ·10 mA cm−2, the overpotentials of the CoS2–C@ReS2/CFP catalyst are 85 and 257 mV during the HER and OER processes with the small Tafel slope, low charge transfer resistance and exceptional catalytic stability. The combination of the CoS2 core and ReS2 shell is designed to adjust the adsorption energy of water molecules, promoting water dissociation, and enhancing the catalytic activity of CoS2–C@ReS2/CFP catalyst. This work provides an efficient strategy for developing the core-shell structured catalysts, potentially advancing the practical application into water splitting for hydrogen production.

Exploring Titanium Dioxide Nanotubes: Pioneering Advanced Applications in Efficient Water Splitting and Sustainable Hydrogen Generation

This interdisciplinary study synthesizes findings from diverse fields including materials science, psychology, and environmental sustainability to explore the multifaceted challenges and opportunities associated with titanium dioxide (TiO2) nanotubes and social media use. In the realm of materials science, TiO2 nanotubes have garnered attention for their potential applications in sustainable energy generation, particularly in water splitting for hydrogen production. Synthesis methods such as hydrothermal synthesis and nitrogen doping have been investigated to enhance the photocatalytic performance and stability of TiO2 nanotubes. Concurrently, the proliferation of social media platforms has transformed communication patterns and behaviors worldwide, shaping individuals' interactions, perceptions, and mental health outcomes. While social media offers opportunities for connectivity and self-expression, excessive use has been associated with adverse mental health outcomes, including symptoms of depression, anxiety, and loneliness. Additionally, social media engagement has been linked to body image dissatisfaction, sleep disturbances, and academic performance, highlighting the complex interplays between online behaviors and psychological well-being. This study integrates insights from a comprehensive review of peer-reviewed literature, encompassing experimental research, observational studies, and survey-based investigations. The synthesis underscores the need for interdisciplinary collaboration and targeted interventions to address the complex societal challenges posed by TiO2 nanotubes and social media use. Recommendations include further research to optimize synthesis methods, enhance regulatory oversight, and promote responsible digital citizenship. By fostering dialogue and collaboration between researchers, policymakers, and practitioners, this study aims to inform evidence-based interventions and policy initiatives to promote sustainability, well-being, and equity in the digital age.

In Situ Growth of Interfacially Nanoengineered 2D-2D WS2/Ti3C2Tx MXene for the Enhanced Performance of Hydrogen Evolution Reactions.

In line with current research goals involving water splitting for hydrogen production, this work aims to develop a noble-metal-free electrocatalyst for a superior hydrogen evolution reaction (HER). A single-step interfacial activation of Ti3C2Tx MXene layers was employed by uniformly growing embedded WS2 two-dimensional (2D) nanopetal-like sheets through a facile solvothermal method. We exploited the interactions between WS2 nanopetals and Ti3C2Tx nanolayers to enhance HER performance. A much safer method was adopted to synthesize the base material, Ti3C2Tx MXene, by etching its MAX phase through mild in situ HF formation. Consequently, WS2 nanopetals were grown between the MXene layers and on edges in a one-step solvothermal method, resulting in a 2D-2D nanocomposite with enhanced interactions between WS2 and Ti3C2Tx MXene. The resulting 2D-2D nanocomposite was thoroughly characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman, Fourier transform infrared (FTIR), and X-ray photoelectron spectroscopy (XPS) analyses before being utilized as working electrodes for HER application. Among various loadings of WS2 into MXene, the 5% WS2-Ti3C2Tx MXene sample exhibited the best activity toward HER, with a low overpotential value of 66.0 mV at a current density of -10 mA cm-2 in a 1 M KOH electrolyte and a remarkable Tafel slope of 46.7 mV·dec-1. The intercalation of 2D WS2 nanopetals enhances active sites for hydrogen adsorption, promotes charge transfer, and helps attain an electrochemical stability of 50 h, boosting HER reduction potential. Furthermore, theoretical calculations confirmed that 2D-2D interactions between 1T/2H-WS2 and Ti3C2Tx MXene realign the active centers for HER, thereby reducing the overpotential barrier.

Harnessing intrinsic defect complexes for visible-light-driven photocatalytic activity in Delafossite CuAlO2

This study significantly enhances the photo(electro)catalytic capabilities of CuAlO2, a wide bandgap semiconductor, through targeted defect engineering. By employing a tailored solid-state reaction under a mixed oxygen-argon atmosphere, an intrinsic defect complex of [Oi+CuAl] into has been successfully integrated into CuAlO2, thereby expanding its light absorption to the visible spectrum. The optimized CuAlO2 sample, containing the [Oi+CuAl] complex, demonstrates a remarkable 2.13-fold increase in photocatalytic degradation of tetracycline hydrochloride under visible-light irradiation. The maximum incident photon-to-current conversion efficiency value is elevated from 0 to 3.27 %, and the photocatalytic water splitting hydrogen production rate is increased by 10.78-fold. Density functional theory calculations, in conjunction with experimental data, elucidate the role of the [Oi+CuAl] complex in facilitating visible-light absorption and improving the separation of photogenerated electron-hole pairs. Under simulated sunlight, the modified CuAlO2 sample exhibits a substantial 2.26-fold enhancement in photocatalytic degradation of tetracycline hydrochloride, a photocurrent density increase from 0.80 to 8.20 µA·cm−2, and a 1.13-fold increase in photocatalytic hydrogen production rate compared to defect-free CuAlO2. This research underscores the potential of strategic defect engineering to enhance visible-light-driven photo(electro)catalysis in wide bandgap semiconductors.

Spatial configuration of Fe–Co dual-sites boosting catalytic intermediates coupling toward oxygen evolution reaction

Oxygen evolution reaction (OER) is the pivotal obstacle of water splitting for hydrogen production. Dual-sites catalysts (DSCs) are considered exceeding single-site catalysts due to the preternatural synergetic effects of two metals in OER. However, appointing the specific spatial configuration of dual-sites toward more efficient catalysis still remains a challenge. Herein, we constructed two configurations of Fe-Co dual-sites: stereo Fe-Co sites (stereo-Fe-Co DSC) and planar Fe-Co sites (planar-Fe-Co DSC). Remarkably, the planar-Fe-Co DSC has excellent OER performance superior to stereo-Fe-Co DSC. DFT calculations and experiments including isotope differential electrochemical mass spectrometry, in situ infrared spectroscopy, and in situ Raman reveal the *O intermediates can be directly coupled to form *O-O* rather than *OOH by both the DSCs, which could overcome the limitation of four electron transfer steps in OER. Especially, the proper Fe-Co distance and steric direction of the planar-Fe-Co benefit the cooperation of dual sites to dehydrogenate intermediates into *O-O* than stereo-Fe-Co in the rate-determining step. This work provides valuable insights and support for further research and development of OER dual-site catalysts.

Three-Dimensional Multihierarchical Hexagonal/Cubic ZnIn2S4 S-Scheme Heterophase Junction for Superior Photocatalysis.

It is an important strategy to design composite materials with a special microstructure and a tunable electronic structure through structural compatibility. In this work, a novel hexagonal/cubic ZnIn2S4 polymorphic heterophase junction with a three-dimensional multihierarchical structure is successfully constructed by in situ growth of hexagonal ZnIn2S4 nanosheets on the surface of cubic ZnIn2S4 flower-like microspheres prepared by topological chemical synthesis. On the one hand, the multihierarchical architecture provides large specific surface area, abundant active sites, and excellent light trapping capability. On the other hand, the construction of a direct S-scheme heterophase junction enables the formation of a special charge-transfer channel under the force of a built-in electric field, which not only improves the separation efficiency of carriers but also ensures the stronger reaction activity of charges. The prepared ZnIn2S4 heterophase junction composite photocatalyst exhibits greatly boosted photocatalytic efficiency in rhodamine B degradation, hexavalent chromium reduction, and water splitting for hydrogen production, which are 12.3, 6.5, and 3.1 times higher than that of pure hexagonal ZnIn2S4 and 8.1, 5.1, and 2.3 times higher than that of pure cubic ZnIn2S4, respectively, demonstrating its significant potential for applications in energy and environmental fields.

Molybdenum-doped Co3S4 nanoarrays as outstanding catalysts for overall water splitting

Developing cobalt-based electrocatalysts that can replace precious metals is significant for hydrogen production in water splitting, however, this is still a complex and demanding task.

Solar light driven atomic and electronic transformations in a plasmonic Ni@NiO/NiCO3 photocatalyst revealed by ambient pressure X-ray photoelectron spectroscopy.

This work employs ambient pressure X-ray photoelectron spectroscopy (APXPS) to delve into the atomic and electronic transformations of a core-shell Ni@NiO/NiCO3 photocatalyst - a model system for visible light active plasmonic photocatalysts used in water splitting for hydrogen production. This catalyst exhibits reversible structural and electronic changes in response to water vapor and solar simulator light. In this study, APXPS spectra were obtained under a 1 millibar water vapor pressure, employing a solar simulator with an AM 1.5 filter to measure spectral data under visible light illumination. The in situ APXPS spectra indicate that the metallic Ni core absorbs the light, exciting plasmons, and creates hot electrons that are subsequently utilized through hot electron injection in the hydrogen evolution reaction (HER) by NiCO3. Additionally, the data show that NiO undergoes reversible oxidation to NiOOH in the presence of water vapor and light. The present work also investigates the contribution of carbonate and its involvement in the photocatalytic reaction mechanism, shedding light on this seldom-explored aspect of photocatalysis. The APXPS results highlight the photochemical reduction of carbonates into -COOH, contributing to the deactivation of the photocatalyst. This work demonstrates the APXPS efficacy in examining photochemical reactions, charge transfer dynamics and intermediates in potential photocatalysts under near realistic conditions.

Advancing strategies on green H2 production via water electrocatalysis: bridging the benchtop research with industrial scale-up

Water splitting provides clean hydrogen via different technologies such as alkaline water electrolysis, proton exchange membrane electrolyzers, solid oxide electrolysis cells, and photoelectrolysis, each with advantages and challenges. The focus on alkaline water electrolysis highlights its maturity compared to emerging methods. Non-noble metal catalysts offer increased stability, low cost and operational lifespan. Challenges such as low current density, gas crossover, corrosive electrolytes, and limited efficiency are still to be addressed. These advanced electrocatalysts are summarized for alkaline oxygen and hydrogen evolution reactions. Meanwhile, different factors including product gas bubble management, operation conditions, separator and electrolyte affecting the performance were concluded and discussed. For the promising approach, seawater splitting is still far from large-scale application. Salinity, pH fluctuations, and complex composition are significant obstacles. The review underscores the need for improvements in electrocatalysts to enhance the efficiency, stability, and practicality of water splitting for hydrogen production, ultimately contributing to the growth of the clean hydrogen market and supporting the transition to sustainable energy systems.