Simultaneous Hydrogen Production Research Articles

BiOClxM1-x (M=I, Br) solid solution-coupled CdS photocatalysts for enhanced visible light-driven organic pollutants degradation with simultaneous hydrogen production

The construction of Z-scheme heterojunction stands out as one of the most effective modification methods for enhancing the performance of photocatalysts. Therefore, BiOClxM1-x (M=I, Br) solid solution-coupled CdS (BiOClxM1-x/CdS) Z-scheme photocatalysts were successfully synthesized by a hydrothermal-precipitation method. BiOCl0.8I0.2/CdS exhibited notable photocatalytic performance with a hydrogen yield of 261 μmol/g, which was 2.23, 1.56 and 1.44 times higher than that of CdS, BiOCl/CdS and BiOCl0.5Br0.5/CdS, respectively. This improvement can be attributed to two key factors: (1) the formation of BiOClxM1-x (M=I, Br) solid solution enhances visible light absorption; (2) The formation of BiOCl0.8I0.2/CdS (M=I, Br) Z-scheme heterojunctions inhibit the recombination of photogenerated carriers to prolong the lifetime of photogenerated carriers, thus increasing the utilization of the photogenerated carriers. Moreover, BiOCl0.8I0.2/CdS also showed good photocatalytic activity in ROW-DFHP (residual organic wastewater from dark fermentation for hydrogen production), with a hydrogen production rate of 42.83 μmol/g and a mineralization rate of organic pollutants of 31.73%. Cycling experiments, XRD and SEM of the samples before and after the photocatalytic reaction showed that BiOCl0.8I0.2/CdS has good stability. Furthermore, the mechanism of BiOCl0.8I0.2/CdS for the photocatalytic degradation of organic pollutants and simultaneous hydrogen production was proposed, offering a novel strategy for organic wastewater purification and hydrogen energy recovery.

Surface exsolving perovskite ceramics as catalyst for microwave methane pyrolysis to co-generate hydrogen and carbon nanotube

In this study, we have successfully developed a novel surface exsolving perovskite ceramic, which demonstrates the ability to simultaneously generate COx-free hydrogen and carbon nanotubes (CNTs) through methane pyrolysis under the influence of microwave irradiation. We conducted an extensive survey and optimization of various perovskite materials specifically tailored for microwave applications. Among the materials investigated, nickel-doped strontium titanium oxide (STON) emerged as the most promising candidate, exhibiting both a satisfactory methane conversion rate and excellent responsiveness to microwave irradiation. Refinement of STON was carried out by fine-tuning the Ni content, optimizing the reduction dwell time, and adjusting the reduction temperature. Notably, SrTiNi0.08O3 (STON8), demonstrated an impressive initial methane conversion rate of up to 40%. Transmission Electron Microscopy (TEM) provided visual evidence of the correlation between Ni content and reduction temperature, with respect to the exsolved Ni metal particle size. This finding highlights the immense potential of surface exsolving perovskite ceramics as a highly effective catalyst for the simultaneous production of CNTs and COx-free hydrogen via methane pyrolysis under microwave irradiation. It represents a step forward in the field of catalytic materials and microwave-driven processes.

Ultrathin Ru/CdIn2S4 nanosheets for simultaneous photocatalytic green hydrogen production and selective oxidation of furfuryl alcohol to furfural

Biomass is an important sustainable carbon source and converting biomass intermediates into value-added chemicals/fuels using a green technology is a promising sustainable pathway. Dual functional photocatalysis can be used to “hit two birds with one stone” via the simultaneous production of H2 and valorisation of the biomass intermediates. CdIn2S4 (CIS), is an exciting photocatalytic material because of its high visible light harvesting capacity. Herein, ultrathin CIS nanosheets were fabricated via a solvothermal method with in situ deposition of Ru (Ru-CIS). The photocatalytic performance of Ru-CIS toward the selective oxidation of furfuryl alcohol (FOH, a biomass intermediate), to a value-added product (Furfural, FCHO) with concurrent generation of hydrogen was investigated. Ru incorporation resulted in up to 50-fold enhancement in hydrogen production rate and higher FOH to FCHO conversion% and selectivity%. This enhancement was attributed to the enhanced charge separation due to the incorporated Ru species as supported by density functional theory (DFT) calculations.

Cascade utilization of full spectrum solar energy for achieving simultaneous hydrogen production and all-day thermoelectric conversion

Solar-driven photocatalytic water/seawater splitting holds great potential for green hydrogen production. However, the practical application is hindered by the relatively low conversion efficiency resulting from the inadequate utilization of solar spectrum with significant waste in the form of heat. Moreover, current equipment struggles to maintain all-day operation subjected to the lack of light during nighttime. Herein, a novel hybrid system integrating photothermal catalytic (PTC) reactor, thermoelectric generator (TEG), and phase change materials (PCM) was proposed and designed (named as PTC-TEG-PCM) to address these challenges and enable simultaneous overall seawater splitting and 24-hour power generation. The PTC system effectively maintains in an optimal temperature range to maximize photothermal-assisted photocatalytic hydrogen production. The TEG component recycles the low-grade waste heat for power generation, complementing the shortcoming of photocatalytic conversion and achieving cascade utilization of full-spectrum solar energy. Furthermore, exceptional thermal storage capability of PCM allow for the conversion of released heat into electricity during nighttime, contributing significantly to the overall power output and enabling PTC-TEG-PCM to operate for more than 12 h under the actual condition. Compared to traditional PTC system, the overall energy conversion efficiency of the PTC-TEG-PCM system can be increased by ∼500%, while maintaining the solar-to-hydrogen efficiency. The advancement of this novel system demonstrated that recycling waste heat from the PTC system and utilizing heat absorption/release capability of PCM for thermoelectric application are effective strategies to improve solar energy conversion. With flexible parameter designing, PTC-TEG-PCM can be applied in various scenarios, offering high efficiency, stability, and sustainability.

Electrochemical treatment coupled with solar light-driven photocatalytic approach: a challenging process in cascade for hydrogen production and wastewater remediation

This study presents an innovative approach for simultaneous hydrogen production and wastewater remediation, integrating electrochemical treatment with solar light-driven photocatalysis. The research focuses on the use of a noble metal-free cathode, based on a electrodeposited composite of Co2P and elemental P, for efficient hydrogen generation from simulated wastewater through water splitting. This composite is characterized, in its optimized form, by an overpotential equal to 133.6mV (at 10mAcm-2) and by a Tafel slope of 60.5mV dec-1. Challenges like the high potential required for the Oxygen Evolution Reaction (OER) and the use of expensive noble metals in electrodes are addressed by employing earth-abundant compounds for electrode fabrication. Additionally, the study explores the degradation of diclofenac (DCF) in wastewater, demonstrating that electrochemical treatment alone is insufficient for organic matter removal. Therefore, a coupled process involving a first electrochemical treatment step followed by a photocatalytic process using BiOCl is proposed. Thanks to the exposure of the (110) active face, BiOCl possesses excellent photocatalytic performances even under solar light irradiation. This hybrid approach not only enhances the efficiency of DCF degradation (about 90%) and reaches an organic matter removal of 59%, but it also improves hydrogen production, offering a sustainable solution for energy generation and water purification in the face of increasing global industrialization and water scarcity.

Optimization of a syngas-fueled SOFC-based multigeneration system: Enhanced performance with biomass and gasification agent selection

In light of abundant sources of biomass feedstocks and regarding the higher performance in syngas-fueled-based SOFC systems, this work proposes a novel multigeneration system based on the combination of syngas-fuel SOFC, Kalina cycle, humidification-dehumidification desalination unit, and proton exchange membrane electrolyzer. This system is designed for simultaneous production of power, heating, freshwater, and hydrogen. Comprehensive energy, exergy, exergoeconomic, environmental, and economic analyses have been conducted to evaluate its performance. The optimum input biomasses, gasification agents, and operating conditions were determined using a coupled approach of an artificial neural network, multi-objective Particle Swarm Optimization algorithm, and the Linear Programming Technique for Multidimensional Analysis of Preference decision-making method. Under base input conditions, the energy and exergy efficiencies of the proposed system were found to be 53.66 % and 38.2 %, respectively. The system also demonstrated the capability to produce 0.1633 kg/s of freshwater and generate a net power output of 377.6 kW. The results indicate that using oxygen-enriched air in the gasification process notably enhances efficiency while reducing emissions. Straw and CO₂ were identified as the optimal feedstock and gasification agent, yielding an exergy efficiency of 42.71 % and a total product cost of 6.29 $/GJ at the optimum point. Moreover, with a selling price of $0.20/kWh for electricity and a fuel cost of $6/GJ, the system can achieve total revenue of approximately $1.65 million with a payback period of 4.01 years. These findings underscore the proposed plant's profitability under specific pricing conditions, making it an attractive investment opportunity.

Valorization of Purple Phototrophic Bacteria Biomass Resulting from Photo Fermentation Aimed at Biohydrogen Production.

This study evaluated the feasibility of contextually producing hydrogen, microbial proteins, and polyhydroxybutyrate (PHB) using a mixed culture of purple phototrophic bacteria biomass under photo fermentative conditions. To this end, three consecutive batch tests were conducted to analyze the biomass growth curve and to explore the potential for optimizing the production process. Experimental findings indicated that inoculating reactors with microorganisms from the exponential growth phase reduced the duration of the process. Furthermore, the most effective approach for simultaneous hydrogen production and the valorization of microbial biomass was found when conducting the process during the exponential growth phase of the biomass. At this stage, achieved after 3 days of fermentation, the productivities of hydrogen, PHB, and microbial proteins were measured at 63.63 L/m3 d, 0.049 kg/m3 d, and 0.045 kg/m3 d, respectively. The biomass composition comprised a total intracellular compound percentage of 56%, with 27% representing PHB and 29% representing proteins. Under these conditions, the estimated daily revenue was maximized, amounting to 0.6 $/m3 d.

A binary dumbbell visible light driven photocatalyst for simultaneous hydrogen production with the selective oxidation of benzyl alcohol to benzaldehyde

Photocatalytic H2 production with selective oxidation of organic moieties in an aqueous medium is a fascinating research area. However, the rational design of photocatalysts and their photocatalytic performance are still inadequate. In this work, we efficiently synthesized the MoS2 tipped CdS nanowires (NWs) photocatalyst using soft templates via the two-step hydrothermal method for efficient H2 production with selective oxidation of benzyl alcohol (BO) under visible light illumination. The optimized MoS2 tipped CdS NWs (20 % MoS2) photocatalyst exhibits the highest photocatalytic H2 production efficiency of 13.55 mmol g−1 h−1 with 99 % selective oxidation of BO, which was 42.34 and 2.21 times greater photocatalytic performance than that of pristine CdS NWs and MoS2/CdS NWs, respectively. The directional loading of MoS2 at the tips of CdS NWs (as compared to nondirectional MoS2 at CdS NWs) is the key factor towards superior H2 production with 99 % selective oxidation of BO and has an inhibitory effect on the photo corrosion of pristine CdS NWs. Therefore, the amazing enhancement in the photocatalytic performance and selectivity of optimized MoS2 tipped CdS NWs (20 % MoS2) photocatalyst is due to the spatial separation of their photoexcited charge carriers through the Schottky junction. Moreover, the unique structure of the MoS2 flower at the tip of 1D CdS NWs offers separate active sites for adsorption and surface reactions such as H2 production at the MoS2 flower (confirmed by Pt photo deposition) and subsequently the selective oxidation of BO at the stem of CdS NWs. This rational design of a photocatalyst could be an inspiring work for the further development of an efficient photocatalytic system for H2 production with selective oxidation of BO (a strategy of mashing two potatoes with one fork).

Brookite TiO2 as an active photocatalyst for photoconversion of plastic wastes to acetic acid and simultaneous hydrogen production: Comparison with anatase and rutile

Photoreforming is a clean photocatalytic technology for simultaneous plastic waste degradation and hydrogen fuel production, but there are still limited active and stable catalysts for this process. This work introduces the brookite polymorph of TiO2 as an active photocatalyst for photoreforming with an activity higher than anatase and rutile polymorphs for both hydrogen production and plastic degradation. Commercial brookite successfully converts polyethylene terephthalate (PET) plastic to acetic acid under light. The high activity of brookite is attributed to good charge separation, slow decay and moderate electron trap energy, which lead to a higher generation of hydrogen and hydroxyl radicals and accordingly enhanced photo-oxidation of PET plastic. These results introduce brookite as a stable and active catalyst for the photoconversion of water contaminated with microplastics to value-added organic compounds and hydrogen.

Pd:In-Doped TiO2 as a Bifunctional Catalyst for the Photoelectrochemical Oxidation of Paracetamol and Simultaneous Green Hydrogen Production.

The integration of clean energy generation with wastewater treatment holds promise for addressing both environmental and energy concerns. Focusing on photocatalytic hydrogen production and wastewater treatment, this study introduces PdIn/TiO2 catalysts for the simultaneous removal of the pharmaceutical contaminant paracetamol (PTM) and hydrogen production. Physicochemical characterization showed a high distribution of Pd and In on the support as well as a high interaction with it. The Pd and In deposition enhance the light absorption capability and significantly improve the hydrogen evolution reaction (HER) in the absence and presence of paracetamol compared to TiO2. On the other hand, the photoelectroxidation of PTM at TiO2 and PdIn/TiO2 follows the full mineralization path and, accordingly, is limited by the adsorption of intermediate species on the electrode surface. Thus, PdIn-doped TiO2 stands out as a promising photoelectrocatalyst, showcasing enhanced physicochemical properties and superior photoelectrocatalytic performance. This underscores its potential for both environmental remediation and sustainable hydrogen production.

Synthesis, characterization and application of tangerine peel-derived Fe3C/Fe-encapsulated biochar for electrochemical removal of environmental pollutant

Conforming to the principles of green chemistry and sustainable environmental progress, this work demonstrated the concept of “treating waste with waste”, i.e. treating atmospheric pollutant sulfur dioxide (SO2) with agricultural waste of tangerine peel. SO2 electro-catalytic oxidation is the key technique in this endeavor, which utilizes SO2 as reaction raw material in the anode to remove it. The anodic SO2 electro-catalytic oxidation could be coupled to the cathodic hydrogen evolution to achieve the simultaneous SO2 removal and hydrogen production. Anodic catalyst plays a vital role in this SO2 transformation. In this work, tangerine peel has been re-utilized to afford tangerine peel-derived biochar (TPB) to prepare TPB/CNT-derived Fe3C/Fe/C (N-doped) as a capable anodic catalyst to achieve this goal. With help of various characterization techniques and electrochemical testing, the optimal iron mass fraction and pyrolysis temperature were found to be 16 wt% Fe under 800 °C, with carboxylated carbon nanotube as carbon additive. Transmission electron microscopy (TEM) image showed that the as-prepared TPB/CNT-derived Fe3C/Fe/C (N-doped) featured a unique morphology to encapsulate Fe3C/Fe with a layer of protecting carbon, which should contribute to the enhanced electro-catalytic performances. A flow electrolyzer was also assembled to illustrate practical application of the anodic catalyst in the real scenario. Owing to its lower cost, the as-prepared TPB/CNT-derived Fe3C/Fe/C (N-doped) will be advantageous to replace precious metals to mediate SO2 electro-catalytic oxidation as one of promising environmental treatment techniques in the future.

Designing and fabricating a neoteric immobilized Z-scheme V2O5/FeVO4/430-stainless steel foil photocatalyst composite film for tetracycline degradation with synchronous hydrogen production

For traditional photocatalyst composite films, the produced hydrogen and carbon dioxide are mixed together, which is not conducive to the direct use of hydrogen. In this study, a novel immobilized Z-scheme V2O5/FeVO4/430-stainless steel foil (V2O5/FeVO4/430-SSF) photocatalyst composite film was constructed. Thereby, the hydrogen and the carbon dioxide can separately generated on both sides of the photocatalytst film and the pure hydrogen can be obtained. The results show that the photocatalyst composite film prepared under optimal conditions has excellent photocatalytic activity in organic pollutant degradation with simultaneous hydrogen production. Under simulated sunlight irradiation for 120 min, the degradation ratio of tetracycline is 77.53% and the hydrogen production amount reaches 370.81 µmol/dm2. It is hoped that this work could provide some guiding suggestions to designing a photocatalyst composite film for efficient photocatalytic degradation of organic pollutants with simultaneous production of pure hydrogen in the future.

Cyan Hydrogen Process: A New Route for Simultaneous Hydrogen Production and Carbon Valorization.

Hydrogen is expected to largely contribute to the near-future circular economy. Today, most hydrogen is still produced from fossil fuels or renewable pathways with low efficiency and high cost. Herein, a proof of concept for a novel hydrogen production process is proposed, here named cyan hydrogen, inspired by a combination of the green and blue processes, due to the key role played by water and the low carbon content in the gas phase, respectively. The developed novel process, recently patented and demonstrated at the lab scale, is based on successive steps in which ethanol (5.0 mL) and water (10.0 mL) are alternately fed, with a fixed initial amount of sodium metaborate (2.0 g), in a batch reactor at 300 °C. Preliminary results showed the simultaneous production of a 95% v/v hydrogen stream, a polymeric byproduct with a repetitive carbon pattern -CH2-CH2-, and a liquid phase rich in oxygenated chemicals at temperatures lower than conventional hydrogen production processes.

Simultaneous hydrogen and methane production by tequila vinasses dark fermentation in series with anaerobic digestion

Biofuels production from agro-industrial residues is a promising alternative for obtaining energy from renewable resources. Here, vinasses (tequila manufacture waste) were used as substrate to an anaerobic system comprised by a Continuous Stirred Tank Reactor (CSTR) with biomass carriers and an Upflow Anaerobic Sludge Blanket reactor (UASB) connected in series. The effect of the organic loading rate on the hydrogen and methane generation was evaluated through increase in fed vinasse concentration. Maximum volumetric production rates of 2.2 L H2/L-d in the CSTR and 0.12 L CH4/L-d in the UASB were obtained when feeding 20 g chemical oxygen demand per liter from vinasse diluted to 60 % of its original concentration. Feeding more concentrated vinasses provoked a decrease in the production of hydrogen and methane, coinciding with a 5 g/L-peak in reducing sugars in the CSTR, suggesting overload and acidification as reasons of the diminished performance. The highest hydrogen and methane equivalent energy obtained in the anaerobic system was estimated to be 2.6 kJ/L-d.

Uncovering the electrooxidation behavior of 5-hydroxymethylfurfural on Ni/Co electrodes

Biomass, derived from plant photosynthesis that captures carbon dioxide to form carbohydrates, offers vast renewable reserves. The electrooxidation of biomass, coupled with the hydrogen evolution reaction, enables the simultaneous production of biomass-based plastic monomers and green hydrogen, attracting significant scholarly interest. However, ambiguity remains regarding the adsorption mechanism at the catalyst surface (Langmuir-Hinshelwood or Eley-Rideal) and the adsorbed substrate groups. To address this, we prepared a Ni/Co electrode for the electrooxidation of 5-hydroxymethylfurfural (HMF) into 2,5-furandicarboxylic acid (FDCA) through a corrosion reaction and electro-reduction pathway. HMF conversion reached 100.00%, FDCA yield reached 96.82%, and Faradic efficiency (FE) reached 92.14%. Meaningfully, utilizing in-situ spectroscopy and electrochemical methods, this work provided valuable insights into active sites and catalyst surface adsorption.

Influence of MgO promoution to Ni-based composites in hydrogen production methane decomposition process

Catalytic decomposition of methane is a promising process that allows the simultaneous production of hydrogen and carbon nanomaterials with no COx emissions. In this work, for the first time, the possibility of promoting Ni-containing composite materials based on an organic matrix of polyvinyl alcohol (PVA) with MgO was demonstrated. The amount of MgO promoter varied from 1 to 10% by weight of Ni. The synthesized catalysts were characterized by the following methods: elemental analysis, TPR-H2, XRD, FTIR spectroscopy, Raman spectroscopy, SEM, TEM, SSA, and Raman fluorescence enhancement spectroscopy. The catalytic activity of the materials was tested in the pure CH4 decomposition reaction. Promotion with MgO contributes to an increase in the H2 yield per unit mass of Ni from 1.23 to 2.55 mol/gNi. The optimal content of the promoting component was 0.3% wt., which corresponded to 1% wt. from Ni. Carbon formed during CH4 decomposition in the form of nanotubes. The obtained carbon nanotubes (CNTs) were characterized by the following methods: XRD, Raman spectroscopy, SEM, and TEM. The length of the CNTs varies from 1 to 6 μm, the outer diameter ranges from 40 to 60 nm, and the inner diameter ranges from 10 to 20 nm.

Preliminary Evaluation of Methods for Continuous Carbon Removal from a Molten Catalyst Bubbling Methane Pyrolysis Reactor

Methane pyrolysis in molten catalyst bubble (MCB) column reactors is an emerging technology that enables the simultaneous production of hydrogen and solid carbon, together with a mechanism for separating the two coproducts. In this process, methane is dispersed as bubbles into a high temperature molten catalyst bath producing hydrogen and low-density carbon, which floats to the surface of the bath from providing a means for them to be separated. However, the removal of carbon particulates from a bubbling column reactor is technically challenging due to the corrosive nature of the molten catalysts, contamination of the product carbon with the molten catalysts, high temperatures and lack of understanding of the technology options. Four potential concepts for the removal of carbon particulate from a methane pyrolysis molten metal bubble column reactor are presented, based on the pneumatic removal of the particles or their overflow from the reactor. The concepts are evaluated using a cold prototype reactor model. To simulate the operation of a high-temperature reactor at low temperatures, the dominant dimensionless numbers are identified and matched between a reference high-temperature reactor and the developed cold prototype using water, air and hollow glass microsphere particles as the representatives of the molten catalyst, gaseous phases and solid carbon particulates, respectively. The concepts are tested in the cold prototype. High rates of particle removal are achieved, but with different tradeoffs. The applicability of each method together with their advantages and disadvantages are discussed.

Simultaneous and Continuous Production of Carbon Nanotubes and Hydrogen by Catalytic CH4 Decomposition in a Pressurized Fluidized-Bed Reactor

Simultaneous and Continuous Production of Carbon Nanotubes and Hydrogen by Catalytic CH₄ Decomposition in a Pressurized Fluidized-Bed Reactor

Simultaneous production of hydrogen and chlorine through overall brine splitting with a particulate photocatalyst.

Sunlight-driven photocatalytic water splitting shows promise for green H2 production. In an attempt to achieve seawater splitting, we constructed a new stoichiometric brine splitting system that produces H2 along with Cl2 instead of O2. Cl2-a more potent high-value-added oxidant than O2-was obtained with 100% selectivity over 10 h by adjusting the solution pH to acidic using a UV-light-driven Pt-loaded TiO2 photocatalyst. Our new photosynthesis system can permit economically feasible solar chemical production.

Solar-driven simultaneous production of hypochlorous acid and hydrogen from saline water over RhCrOx-loaded SrTiO3 photocatalyst systems

Photocatalytic simultaneous production of HClO and H2 in saline water under simulated solar light was successfully achieved on SrTiO3:Al photocatalyst systems.