H2 Production Research Articles

Operational long-term management of a salt cavern for industry targeted green H2 production

Hydrogen and its derivatives such as ammonia are increasingly important for reducing carbon emissions in sectors with limited alternatives. Large production systems are generally preferred to reduce costs and for those, advanced management is a cornerstone to the project economic viability. The present work explores the development of an Energy Management System for an industrial low-emission ammonia production platform. The latter is connected to the electrical grid and consists of 1.5 GW of renewable production units, around 500 MW of electrolyzers and storage facilities including especially a salt cavern for H2 storage. The long-term management of the salt cavern is decisive to enhance the profitability while satisfying industry related constraints such as the carbon content of the produced H2. The literature lacks in addressing both aspects simultaneously. Methodological approaches to tackle the long-term management and industrial constraints are proposed and compared. For the considered platform, it is shown that a strategy based on precalculated cost functions in the long term horizon allows relative gains of 2.5% with respect to a state-of-the-art short term management leading to an annual cost saving of approximately $6.2 million in the platform operational expenses. This translates to a reduction of the gap between the state-of-the-art and the optimal a posteriori solution by about 82%.

Piezoelectric field accelerating charge transfer in Z-scheme heterojunction 2D-KNbO3/1D-CdS for efficient piezo-photocatalytic H2 evolution and TCH degradation

The piezo-phototronic effect utilizes the piezoelectric polarization field to tune the photogenerated carrier separation and transport performance in heterojunctions, which portrays a promising strategy for addressing energy shortage and environmental pollutants. Herein, a novel Z-scheme piezoelectric semiconductor heterojunction, 2D-KNbO3/1D-CdS-x (KNCS-x), was fabricated using hydrothermal and solvothermal methods, resulting in enhanced redox capacity. Under the simultaneous light and strain, KNCS-15 exhibits the highest piezo-photocatalytic activity, with degradation rates of tetracycline hydrochloride degradation rate constant, H2O2 as well as H2 production rates being 1.806 × 10−2s−1, 45.56 mM·h−1·g−1 and 8.87 mmol·h−1·g−1, respectively, which are 1.4, 2.4 and 1.9 times of photocatalysis alone, and 9.8, 9.2 and 9.8 times of piezocatalysis alone. DFT calculations, EPR and PALS indicate that the Z-scheme structure realizes effective separation of electron-hole pairs with strong redox ability and a higher carrier concentration. The enhanced catalytic activity is attributed to the introduction of piezoelectric potential, which facilitates improved spatial separation of electrons with high reduction and holes with high oxidation potential.

Impact of Dual Functionalities of Mo‐Doped BiFeO3 Decorated with Bi4MoO9 Heteroatoms for Piezo‐Photocatalytic Activity

AbstractPiezocatalysts have shown great promise for effcient hydrogen generation. However, their application is limited by the rapid charge recombination and sluggish charge transfer rate of piezo‐induced charge carriers. This work aims to address the preceding limitations by controlled synthesis of a representative piezocatalyst, BiFeO3 doped with Mo atoms and decorated with Bi4MoO9 (BMO) heteroatoms using sol‐gel method. The substitutional doping of Mo on BFO (BFMO) was shown to induce a shallow energy level near the conduction band that acted as a trapping state, to suppress recombination of charge carriers, enhance charge mobility for transport to the surface, modulate band alignment, and lower the energy barrier for surface reaction. The formation of BFMO/BMO heterostructures induced electrical band bending, leading to the electric potential gradient, hence promoting charge carrier separation and transfer. The BFMO/BMO with 0.5 mol % Mo (Mo‐5) demonstrated four times faster piezocatalytic Rhodamine B (RhB) dye degradation rate (k of 0.032 min−1) compared to pristine BFO (0.009 min−1). Further, the Mo‐5 exhibited a 45% higher piezocatalytic H2 production rate (14.4 µmol/g/h) compared to pristine BFO (9.8 µmol/g/h) while being cocatalyst‐free. Coupling piezocatalysis with photocatalysis was found to reduceperformance relative to the individual processes, which is attributed to Auger recombination which impedes any potential synergistic effect.

Magnesium Hydride Confers Osmotic Tolerance in Mung Bean Seedlings by Promoting Ascorbate–Glutathione Cycle

Despite substantial evidence suggesting that hydrogen gas (H2) can enhance osmotic tolerance in plants, the conventional supply method of hydrogen-rich water (HRW) poses challenges for large-scale agricultural applications. Recently, magnesium hydride (MgH2), a hydrogen storage material in industry, has been reported to yield beneficial effects in plants. This study aimed to investigate the effects and underlying mechanisms of MgH2 in plants under osmotic stress. Mung bean seedlings were cultured under control conditions or with 20% polyethylene glycol (PEG)-6000, with or without MgH2 addition (0.01 g L−1). Under our experimental conditions, the MgH2 solution maintained a higher H2 content and longer retention time than HRW. Importantly, PEG-stimulated endogenous H2 production was further triggered by MgH2 application. Further results revealed that MgH2 significantly alleviated the inhibition of seedling growth and reduced oxidative damage induced by osmotic stress. Pharmacological evidence suggests the MgH2-reestablished redox homeostasis was associated with activated antioxidant systems, particularly the ascorbate–glutathione cycle. The above observations were further supported by the enhanced activities and gene transcriptional levels of ascorbate peroxidase, monodehydroascorbate reductase, dehydroascorbate reductase, and glutathione reductase. Overall, this study demonstrates the importance of MgH2 in mitigating osmotic stress in mung bean seedlings, providing novel insights into the potential agricultural applications of hydrogen storage materials.

Facile sol-gel synthesis of ZnAl2O4 spinel nanoceramics for photocatalytic applications: H2 production and MB dye degradation

Facile sol-gel synthesis of ZnAl2O4 spinel nanoceramics for photocatalytic applications: H2 production and MB dye degradation

In situ synthetic H2 on composite cathode surface for CH4 production from CO2 in microbial electrosyntshesis

Microbial electrosynthesis (MES) is an innovative technology that employs microbes to synthesize chemicals by reducing CO2.This study explores the CH4 production performance at different cathodic reduction potentials in MES. In this study, in situ H2 production on the surface of composite electrode was realized by regulating cathode potential. Pathway for H2-mediated CH4 synthesis was the main synthesis pathway, but it was susceptible to interfere from the external environment (such as cathode potential, pH). The optimal CH4 production potential was −1.0 V vs Ag/AgCl, meanwhile the CH4 synthesis rate was 58 ± 0.4 mLm−2d−1 and the CE was 67 ± 0.5%. Excessively high reduction potentials (−1.4 V vs Ag/AgCl) reduce the activity of microbial populations at the cathode. Synergistic interactions between H2-producing bacteria (Hydrogenophaga, Clostridium, Enterobacter, and Escherichia coli) and Hydrogenotrophic methanogens (Methanobacterium and Methanomassiliicocus) promoted efficient synthesis of CH4. These insights provide new perspectives on reactor operation, thus contributing to the efficiency of MES.

Effect of Ni/Co ratio on Ce-Sc-ZrO2 catalysts for selective H2 production via methane partial oxidation

Partial oxidation of methane (POM) is a promising route for hydrogen production, and achieving a high H2 yield with an H2/CO ratio >3 is highly appealing. Optimization of Ni/Co ratios over Ce-Sc-ZrO2 (CSZ) is investigated for POM reaction and characterized by X-ray diffraction, Raman spectroscopy, temperature-programmed reduction/oxidation/desorption, and transmission electron microscopy. The active site derived from the reduction of “strongly interacted NiO” is responsible for the dissociation of C–H (of CH4), resulting high activity towards POM. 5Ni/CSZ has the highest amount of such active sites and attains the highest activity. 5Co/CSZ catalyst has cobalt-based active sites, and there is an inert carbon deposit during the reaction, causing the least activity. 3.75 wt% Ni and 1.25 wt% Co combination over CSZ support surges the highest density of basicity, oxide vacancy, and adequate amount of active sites derived from “strongly interacted NiO”. The active sites with enhanced metal-support interaction are further grown under exposure to oxidizing gas (O2) and reducing gas (H2) during the POM reaction. The highest density of basicity and oxide vacancy involves more CO2 and H2O in the sequential oxidation of CH4 under indirect pathways. The exclusive involvement of indirect pathways of POM and inhibition of hydrogen consuming reaction (like reverse water gas shift reaction) over 3.75Ni1.25Co/CSZ results into 48 % H2 yield and 3.26 H2/CO ratio up to 24 h time on stream at 600 °C. The H2 yield doubles to ∼97 %, and the H2/CO ratio comes close to 2 over 3.75Ni1.25Co/CSZ catalyst at 900 °C.

Comparative energy, emissions and economic assessment of low-carbon iron and steel making processes using imported liquid organic hydrogen carrier options

Hydrogen (H2)-based steel making is expected to become a major driver of intercontinental low-carbon H2 imports. Eight H2 supply scenarios based on either local H2 production at major steel producing locations (Germany/Japan), or liquid H2 carrier (dibenzyltoluene/perhydrodibenzyltiluene, DBT/PDBT) import from the United Arab Emirates, and their integration with H2 direct reduced iron (H-DRI) and electric arc furnace (EAF) processes, are investigated using process modeling. Solar energy-based PDBT import using surplus heat for dehydrogenation is the most cost-competitive H2 import scenario in Germany's case (levelized steel production cost, ∼685 $/tLS, with carbon emissions, ∼237 kgCO2/tLS). In Japan's case this scenario is the most economically favorable of all scenarios (∼736 $/tLS), with emissions (∼350 kgCO2/tLS) comparable to natural gas-DRI-EAF with 50% carbon capture. Steam methane reforming with carbon capture-based PDBT import is neither environmentally nor economically viable. PDBT-based H-DRI-EAF production cost is sensitive to electricity, H2 production, dehydrogenation energy, and carbon costs.

Unraveling the mechanism of CH3CH2OH dehydrogenation on m-ZrO2(111) surface, Au13 cluster, and Au13 cluster/m-ZrO2(111) surface: A DFT and microkinetic modeling study

The dehydrogenation of CH3CH2OH to produce CH3CHO and H2 is crucial for generating valuable chemicals. This study uses density functional theory (DFT) and microkinetic modeling to elucidate the reaction pathways on the m-ZrO2 (111) surface, Au13 cluster, and Au13 cluster/m-ZrO2(111) surface. Dehydrogenation on both the m-ZrO2(111) surface and Au13 cluster occurs via two key steps. The first step involves the cleavage of the OH bond in CH3CH2OH, forming a CH3CH2O moiety and an OH bond with the lattice oxygen on m-ZrO2 (111) surface or with a low-coordination Au atom in the Au13 cluster, respectively; while the formation of H2 takes place in the second step; however, the results microkinetic modeling render low values for the corresponding rate constants for this reaction path. Although the Au13cluster/m-ZrO2(111) surface introduces an additional step, where the H atom migrates from the m-ZrO2 (111) surface to the Au13 cluster, we shown that the relative energy of the three transition states is similar, the activation barriers are lower, and the rate constants are favorable for the dehydrogenation of CH3CH2OH. These results demonstrate the potential of the Au13 cluster supported on m-ZrO2(111) for efficient and selective CH3CHO and H2 production, providing valuable insights for advanced catalytic system design.

ZnO with Different Morphologies Sensitized by Metalloporphyrins as Catalysts for H2 Production by Water Splitting under Sunlight.

In this work, zinc oxide with different morphologies and textural properties were prepared and sensitized with metalloporphyrins (MPs) aiming to improve its solar energy harvesting capability for H2 production by water splitting under sunlight (a 300 W Xe/Hg lamp). An anionic iron(III)porphyrin and a cationic manganese(III)porphyrin were immobilized on different ZnO solids predominantly by electrostatic interactions. In general, the prepared MP-free ZnO solid yielded modest catalytic results which had apparently no direct correlation with their textural properties or morphology. On the other hand, when these ZnO solids had iron or manganese porphyrin sensitizing them, their catalytic performances changed and a superior yield towards H2 production was observed in comparison to the pure ZnO solids, making evident the synergy achieved between these two components (ZnO and metalloporphyrins) for the prepared solids. It was also observed that the metalloporphyrins and the respective free-base ligand suffered redox reactions when used as homogenous catalyst in this reaction, which could influence their performances as catalysts. The same was not observed in the solids containing immobilized MP, suggesting some protective effect of the ZnO solids on the MP complexes upon immobilization probably due to interaction of the complexes with the ZnO matrix.

Oriented Crystal Polarization Tuning Bulk Charge and Single-Site Chemical State for Exceptional Hydrogen Photo-Production.

Rapid bulk charge recombination and mediocre surface catalytic sites harshly restrict the photocatalytic activities. Herein, the aforementioned concerns are well addressed by coupling macroscopic spontaneous polarization and atomic-site engineering of CdS single-crystal nanorods for superb H2 photo-production. The oriented growth of CdS nanorods along the polar axis, vectorially superimposing substantial polar units with orderly arrangement, renders a strong polarization electric field (20.1 times enhancement), which boosts bulk charge separation with an efficiency up to 72.4% (80.4-fold). Remarkably, polarization electric field alters the chemical state of Pt single sites by orderly reducing the binding energy of Pt atom with stepwise polarization enhancement of CdS substrate, which increases the onsite electron density of Pt from 10.232 to 10.261e- and *H key intermediates, providing preponderant Volmer-Tafel/Volmer-Heyrovsky reaction pathways with significantly decreased energy barriers for H2 production. Thus, highly polarized CdS nanorods with atomically dispersed Pt sites perform an outstanding H2 space-time yield of 118.5mmol g-1 h-1 and apparent quantum efficiency of 57.7% at λ = 420nm, and a record-high H2 turnover frequency of 57798.4 h-1, being one of the best catalysts for photocatalytic H2 evolution. This work highlights the function of polarization in manipulating charge separation and catalytic reaction.

Industrial-scale 12-layered-bed vacuum pressure swing adsorption for fuel cell-grade H2 production from carbon-captured steam methane reforming syngas

Vacuum pressure swing adsorption (VPSA) is primarily used to produce high-purity H2 from CO2-rich syngas in steam methane reforming (SMR) plants. Since carbon capture is essential, the performance of current H2 VPSA processes is affected by feeding carbon-captured SMR syngas (CO2-lean SMR syngas). This study conducted the performance evaluation and optimization for a fuel cell-grade H2 production by an industrial-scale 12-layered-bed VPSA process with a 24-step cycle from CO2-lean SMR syngas. The multi-scale dynamic model for the VPSA process was validated with petrochemical industry data from a current SMR-VPSA plant. A sensitivity analysis using CO2-lean SMR syngas indicated the high loss of H2 during desorption steps, suggesting the need for optimization of the VPSA process. Owing to the complex interconnectivity of 12 beds via 24 steps, the framework of a dynamic model-based deep neural network (DNN) and DNN-based optimization was developed to design and optimize the VPSA process. Even without changing equipment or adsorbent configuration, the VPSA process achieved fuel cell-grade H2 production (>99.9999 % H2 and > 88 % recovery with < 0.2 ppm CO). The results indicate that CO2 capture rates, ranging from 90 to 99 %, can be independently determined under techno-economic and environmental conditions, as this capture range of CO2-lean SMR syngas gives a minor impact on the performance of VPSA process. The proposed three-step framework, which encompasses dynamic modeling, surrogate modeling, and multi-objective optimization, provides a systematic and feasible approach for designing and optimizing the VPSA process in an SMR plant integrated with a carbon capture process, to achieve a low-carbon economy.

Urea-induced low crystallization of Rh nanoparticles for efficient H2 production

Developing highly efficient catalysts for the hydrogen evolution reaction (HER) is crucial for advancing renewable hydrogen energy technologies. Heterophase nanomaterials have shown great promise in catalysis, owing to the synergistic effect among various phases and the abundance of active sites located at the phase boundaries or interfaces. However, achieving precise control over these phase structures during synthesis remains a significant challenge. In this work, we explored a one-pot synthesis method for amorphous/crystalline heterophase Rh nanoparticles, with crystallinity tunable by adjusting the quantity of urea and reaction duration. Due to the increased electrochemical active sites, enhanced electron transport, the resulting amorphous/crystalline heterophase Rh exhibits superior HER activities in both acidic (with an overpotential of 27 mV) and alkaline media (with an overpotential of 21 mV), surpassing that of commercial Pt/C and crystalline Rh. Theoretical calculations indicate that the amorphous/crystalline structure reduces the kinetic barrier for water splitting and optimizes adsorption free energy of hydrogen (ΔGH∗), thereby enabling the catalyst to exhibit significantly enhanced HER performance. This exploration offers a valuable reference for designing amorphous/crystalline heterophase structures and demonstrates the great potential of phase engineering strategy in the development of electrocatalysts.

Ultrafine Pd nanoparticles confined in naphthalene-based covalent triazine frameworks for efficient and stable hydrogen production from formic acid

Formic acid (FA) is considered as a kind of promising hydrogen storage materials due to its economic feasibility, safety, stability and high hydrogen density. Nevertheless, it is a challenge to design a high-performance catalyst with high activity, selectivity and stability for the dehydrogenation of FA to generate hydrogen (H2). Herein, a range of covalent triazine frameworks (CTFs including 1,8-CTF, 1,5-CTF and 2,3-CTF) with abundant nitrogen atoms are developed to support palladium nanoparticles for efficiently catalyzing FA dehydrogenation. Ultrasmall palladium nanoparticles with a size of 1.2 ± 0.3 nm showed near 100 % H2 selectivity and high catalytic activity in FA dehydrogenation supported by 1,8-CTF. The activation energy of FA dehydrogenation catalyzed by Pd/1,8-CTF reaches 26.17 kJ·mol−1. In addition, Pd/1,8-CTF exhibits high stability and easy recyclability, and the catalytic activity is maintained even after 6 cycles. This work gives a feasible strategy to develop high-efficiency and selective nanocatalysts for H2 production from FA dehydrogenation.

Deciphering electrocatalytic hydrogen production in water through a bioinspired water-stable copper(II) complex adorned with (N2S2)-donor sites.

Electrocatalytic hydrogen production stands as a pivotal cornerstone in ushering the revolutionary era of the hydrogen economy. With a keen focus on emulating the significance of hydrogenase-like active sites in sustainable H2 generation, a meticulously designed and water-stable copper(II) complex, [Cl-Cu-LN2S2]ClO4, featuring the N,S-type ligand, LN2S2 (2,2'-((butane-2,3-diylbis(sulfanediyl))bis(methylene))dipyridine), has been crafted and assessed for its prowess in electrocatalytic H2 production in water, leveraging acetic acid as a proton source. The molecular catalyst, adopting a square pyramidal coordination geometry, undergoes -Cl substitution by H2O during electrochemical conditions yielding [H2O-Cu-LN2S2]2+ as the true catalyst, showcases outstanding activity in electrochemical proton reduction in acidic water, achieving an impressive rate of 241.75 s-1 for hydrogen generation. Controlled potential electrolysis at -1.2 V vs. Ag/AgCl for 1.6 h reveals a high turnover number of 73.06 with a commendable Faradic efficiency of 94.2%. A comprehensive analysis encompassing electrochemical, spectroscopic, and analytical methods reveals an insignificant degradation of the molecular catalyst. However, the post-CPE electrocatalyst, present in the solution domain, signifies the coveted stability and effective activity under the specified electrochemical conditions. The synergy of electrochemical, spectroscopic, and computational studies endorses the proton-electron coupling mediated catalytic pathways, affirming the viability of sustainable hydrogen production.

Direct Hydrogen Production Promoted by Laser-Induced Water Plasma.

Hydrogen, as a clean energy carrier, plays an important role in addressing the current energy and environmental crisis. However, conventional hydrogen production technologies require extreme reaction conditions, such as high temperature, high pressure, and catalysts. Herein, we study the microscopic mechanism of laser-induced water plasma and subsequent H2 production with real-time time-dependent density functional theory simulations and ab initio molecular dynamics simulations. The results demonstrate that intense laser excites liquid water to generate nonequilibrium plasma in a warm-dense state, which constitutes a superior reaction environment. Subsequent annealing leads to the recombination of energetic reactive particles to generate H2, O2, and H2O2 molecules. Annealing rate and laser wavelength are shown to modulate the product ratio, and the energy conversion efficiency can reach ∼9.2% with an annealing rate of 1.0 K/fs. This work reveals the nonequilibrium atomistic mechanisms of hydrogen production from laser-induced water plasma and shows far-reaching implications for the design of optically controllable hydrogen technology.

Unravelling the efficiency of CoAl-LDH / g-C3N4 nanosheets: Type-II heterojunction for photocatalytic hydrogen production and dye degradation under solar light irradiation

The generation of hydrogen fuel, and wastewater treatment according to solar-driven catalysis possesses considerable prospective for establishing a carbon-neutral and ecologically sound power infrastructure. Driven by this problem, we suggest in this study, adopting a simple impregnation method, a customized association of CoAl-LDH and graphitic carbon nitride (CN), a visible light active narrow and wide band gap semiconductors. Several characterization approaches were implemented to understand the CoAl-LDH@g-C3N4 (CACN) composites' physiochemical and optical features. The CACN hetero structural forms exhibited significantly improved solar light-induced photocatalytic H2 generation and dye pollutants decomposition in contrast with pristine materials. The most effective catalyst 5 wt% CoAl-LDH@g-C3N4 (5-CACN) generated the highest hydrogen (∼430.7 μmolg−1h−1), which is 11.9-fold H2 production efficiency compared with CN and depicted significant Brilliant black dye removal efficacy via photocatalytic degradation (up to ∼79%). This was primarily ascribed to the development of the Type-II CACN heterojunctions, which promoted the separation of charges and expanded the abundance of surface-active sites while absorbing the visible spectrum of solar light.

Ingenious regulation and activation of sites in the 2H-MoS2 basal planes by oxygen incorporation for enhanced photocatalytic hydrogen evolution of CdS

The 2H phase of MoS2 has the advantages of stable phase structure and tunable preparation approach, while the unfavorable H adsorption ability at the basal plane sites hinders the H2 evolution performance. Here, we developed an effective strategy for the regulation of the basal plane properties of MoS2 via oxygen doping. It is demonstrated that the Gibbs free energy of hydrogen adsorption (ΔGH*) at the sites in the basal plane can be effectively optimized. Using oxygen-doped MoS2 (OMoS) as a cocatalyst, the constructed OMoS/CdS heterojunction photocatalyst shows a stronger built-in electric field and improved photocatalytic H2 production activity. The optimized OMoS/CdS sample with only 0.3 wt% OMoS loading amount achieved an H2 evolution rate of 58.47 mmol g-1h−1 under AM 1.5 light irradiation, which is significantly superior to that of conventional MoS2 modified CdS and even higher than the 1 wt% Pt modified CdS. Our results not only highlighted the significant potential of OMoS as a photocatalyst for hydrogen production, but also proposed a superior to and effective conception for optimizing the H2 evolution activity at the basal plane sites of 2H-MoS2.

Droplet microreactor continuous synthesis of hierarchical Rh on CdZnS snowflakes for enhanced photocatalytic hydrogen evolution

Promising droplet microreactor-cation exchange strategy is utilized to construct the unique Rh hierarchical structure (RhHS) and Rh nanoclusters (RhNCs) on CdZnS (CZS) snowflakes. The fabricated RhHS/RhNCs/CZS achieves an optimal hydrogen evolution activity of 926.0μmol h−1 g−1, which is 5.9 and 10.5 folds enhancement that of CZS and CdS, respectively. The enhanced activity for H2 generation can be attributed to the RhHS/RhNCs (accelerating electron transfer), as well as the hierarchical structure of RhHS and CZS, which enhances reflection–absorption of visible light. Theoretical calculations reveal that Rh species can serve as new H* generation-release sites, reducing the energy barrier for hydrogen evolution. Notably, in situ Raman confirmed the Rh (Rh-H) and S (S-H) two main active sites for proton reduction during hydrogen generation. This paper provides a novel approach to constructing hierarchical structure photocatalyst (RhHS/RhNCs/CZS) for enhanced photocatalytic H2 production.

Improved hydrogen production in immobilized Chlamydomonas reinhardtii cells with inhibited inter-photosystem electron transfer

The production of molecular hydrogen (H2) by microalgae holds great promise, and immobilization techniques offer potential for further advancement in this field. The current study focuses on investigating the positive impact of immobilization on maintaining the stability and activity of photosystem II (PSII) over incubation time, with the aim of enhancing H2 production potential in green microalgae Chlamydomonas reinhardtii. For this purpose, immobilized cells within alginate beads were treated with small concentrations of 2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone (DBMIB) inhibitor to induce the partial inhibition of inter-photosystem electron transport, recently reported as a novel approach for sustaining microalgal H2 production. A comparative analysis of fluorescence decay kinetic changes and EPR spectroscopy of the cell beads revealed the superior capacity of immobilization for sustaining PSII stability and activity in batch culture over time. Treatment of the cell beads with 3.5 μM DBMIB led to sustained H2 production yielding over 200 μmol H2/mg Chl within 3 weeks, with an average H2 production rate of approximately 10 μmol/mg Chl per day, both of which were roughly twice as high as those observed in free cells treated with DBMIB. Our findings underscore the significance of integrating immobilization with a proven and effective method for H2 production, thereby enhancing its sustainability and productivity.