Maximum H2 Yield Research Articles

Interference mechanism of electrolyte cations on vanadium-oxygen binary doped carbon nitride for hydrogen evolution from artificial seawater splitting: Coupling experiments, DFT calculations and machine learning

Photocatalytic H2 production from seawater splitting is a promising method for sustainable energy conversion technology. The vanadium-oxygen binary doped carbon nitride (VOX-CN) is successfully prepared for H2 production. Benefiting from the electronic structure alteration, the maximum H2 yield on VOX-CN in artificial seawater reaches 4475.74 μmol h−1g−1, 10 times higher than that of CN in deionized water. The impact of ions on the photocatalytic activity of VO2-CN is followed by Na+ > Mg2+ > K+ > Ca2+. The adsorption of electrolyte ions promotes the formation of delocalized electron clouds on the surface of VO2-CN, facilitating more electrons to participate in H+ reduction. Screening based on six machine models, the decision tree regression algorithm is used to reveal the interaction between cation type, their concentration and H2 yield. Pearson heatmap indicates that Na+, Mg2+, and K+ ions are positively correlated with H2 yield, whereas Ca2+ shows a negative correlation. The interactions among Na+, Mg2+ and K+ atoms facilitate H2 production in multi-ion system, whereas Ca2+ ions do the opposite, especially for high concentration. This work proposes new insights into the interference on H2 yield between the structure alteration of CN framework and the change of ion type and concentration.

Self-adaptable HAc/NaAc buffer system enhanced biohydrogen production from dark fermentation of cellulose

ThepHdecrease caused by potential accumulation and dissociation of organic acidsis considereda major challenge hindering stable and constant operation in hydrogen production. In this study, a self-adaptableHAc/NaAc buffer system was investigated based on batch dark fermentation hydrogen production (DFHP) metabolic typesto controlthe pH of fermentation process. Resultsshowedthat increasing substrate concentration resulted in lower H2 production yield, especially when the substrate concentration exceeded 10 g/L. A maximum H2yield of2326.25 mL/L was achieved at the HAc/NaAc-buffered group; productions were 2.84 times and 57.7 % higher than the control and NaOH control groups. Our buffersystem retardedthe decrease of pH, enhanced the selectivemetabolic flux of acetic acid production, promoted the growth of microorganisms, enhanced microbial secretion of cellulase, andregulatedthe ratio of NADH/NAD+. The research provided a preliminary understanding and reference for the buffer regulatory strategy on organic waste for DFHP.

Experimental investigation of steam and carbon dioxide influence on methane filtration combustion in a reversal flow porous media reactor

A reverse flow porous medium reactor with premixed and non-premixed flames was experimentally investigated to evaluate the influence of steam and carbon dioxide on methane (CH4) filtration combustion for syngas production. Premixed, non-premixed, and non-premixed with steam were the tested cases for different injection configurations. Thermal profiles, combustion products, hydrogen (H2) and carbon monoxide (CO) yields for several equivalence ratios are analyzed. Non-premixed case exposed higher maximum temperatures due to the reactant accumulation at the crosswise injection position, with a temperature of 1615 K. The lack of homogenization of the reactants in this configuration leads to low H2 and high CO concentrations compared to the premixed case. The maximum CO yield was 92.81% for the non-premixed configuration with alternated air injection, while the maximum H2 yield was 37.8% for the premixed air-methane-steam case. It was found that the air-methane-carbon dioxide mixtures had lower temperatures, combustion wave velocities, and H2 and CO concentrations, compared to the air-methane, and air-methane-steam mixtures, but higher CH4 and CO2 concentrations. The premixed configuration with air-methane-carbon dioxide mixture showed higher temperatures, and H2 and CO concentrations, compared to the non-premixed configuration. Further studies are necessary to optimize the operation of these types of reactors.

Upcycling heteroatoms-containing plastics via bimetallic synergistic catalysis: Unveiling the role of O and Cl in C-H bond cleavage

Given the complicated compositions and hazards of heteroatoms-containing plastics, the efficient upcycling remains a huge challenge. Herein this work proposed an innovative route via dual-stage pyrolysis-catalysis platform to upcycle heteroatoms-containing plastics for high-purity H2 and carbon nanotubes (CNTs) production. Among HY-supported metallic catalysts, bimetallic Fe-Co/HY achieved the maximum H2 yield (41.25 mmol/gplastic) and selectivity (71.76 vol%), alongside the carbon production of 520 mg/gplastic, revealing a catalytically synergistic effect between Fe and Co. Of the plastic individuals/combinations, the plastic combination (PW2) revealed the highest hydrogen efficiency (87.03 %) and H2 efficiency (49.71 %). Regarding the interactions among polyolefins, polyesters, Cl-containing plastics, ternary plastics (PE-PET-PVC) exhibited the higher H2 yield (35.33 mmol/gplastic), hydrogen efficiency (91.40 %), and H2 efficiency (49.14 %) than individual counterparts. The CNTs yield and purity gained from ternary PE-PET-PVC even outperformed these results obtained from individual PE (yield: 326.7 mg/gplasticvs 323.9 mg/gplastic; purity: 93.5 % vs 90.3 %). That was because the chlorinated aryloxy radicals generated from PVC and PET facilitated the cleavage of C (sp3)-H bonds, thereby enhancing the hydrogen extraction and carbon formation. Besides, NiO and NiAl2O4 on the catalyst were converted into NiCl2 by PVC-derived Cl· or HCl, subsequently being reduced into reactive Ni0. Additionally, bimetallic Ni-Fe/HY during CO2-mediated pyrolysis-catalysis displayed the highest H2 yield (55.67 mmol/gplastic), syngas purity (82.39 %), H2 efficiency (62.34 %), and CNTs yield of 367 mg/gplastic, reflecting an apparent synergistically catalytic effect between Ni and Fe. Overall, this study provides a superb solution in heteroatoms-containing plastics upcycling and greenhouse gas emission management.

Optimizing hydrogen yield in sorption-enhanced steam methane reforming: A novel framework integrating chemical reaction model, ensemble learning method, and whale optimization algorithm

High hydrogen production is essential in sorption-enhanced steam methane reforming (SE-SMR). This study presents an innovative optimization framework to optimize the H2 yield of SE-SMR through a coupled reaction model, prediction surrogate model, and whale optimization algorithm. Firstly, a computational fluid dynamics chemical reaction model of SE-SMR is constructed. A database is established to consider the H2 yield of SE-SMR with temperature, pressure, velocity, and steam to carbon ratio. Then, a surrogate model is developed on the basis of eXtreme Gradient Boosting (XGBoost) to predict the H2 yield under various operating parameters. Finally, the surrogate model is exploited to calculate the fitness function of the whale optimization algorithm to construct an optimization framework for maximizing the H2 yield. The results show that the XGBoost ensemble surrogate model can predict the H2 yield of SE-SMR within 4 s with high accuracy. The optimization framework can optimize the maximum H2 yield and the corresponding operating parameters within 1 min. The optimization results are validated by applying the model and the percentage error of only 0.79 %. Moreover, under optimal operating conditions, methane is almost completely converted to hydrogen, and the dry hydrogen mole fraction could reach 95.96 %. The presented optimization framework can guide the prediction of H2 yield and the optimization of operating parameters in SE-SMR.

Low temperature hydrogen production from H2S with metal tin by cyclic two-step method

Hydrogen sulfide (H2S) is not only a highly toxic and corrosive gas commonly present in the natural gas reservoir, but also valuable resource rich in hydrogen and sulfur. The Claus process is commonly used in industry to handle H2S, but it has the disadvantages of generation of SO2 and waste of hydrogen resources. Alternatively, cyclic two-step decomposition of H2S can generate H2 at low temperatures, which has been testified recently. Herein we report a method of splitting H2S into H2 and S with Sn metal in two steps at a low temperature for the first time. The experimental results demonstrate that the maximum yield of H2 can reach 33% at temperatures as low as 300 °C, and the metal Sn could be regenerated at elevated temperature. This research presents a novel approach for the decomposition of H2S to produce H2 and sulfur under relatively mild conditions, thereby opening up further opportunities for future studies on the value-added utilization of H2S.

Hydrogen production from sodium borohydride using Co nanoparticles

In this study, hydrogen [H2(g)] production from sodium borohydride (NaBH4) using cobalt (Co) nanoparticles (NPs) was investigated with a hydrolysis process. Optimum experimental conditions were examined at different hydrolysis times (5, 10, 20, 30, 40, 50, 60, 70, 80, and 90 min), at different hydrolysis temperatures (25, 35, 45, and 65oC), and at increasing Co NPs nanocatalyst concentrations (5, 15 and 30 mg/l) at pH = 13.0, respectively. X-ray diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM) and Transmission Electron Microscopy (TEM) analyses were performed for characterization studies. H2(g) measurements were made in gaschromatography–mass spectrometry (GC-MS). The maximum 81% H2(g) yield was observed before the hydrolysis process after 90 min, at pH = 13.0, at 25 oC. The maximum H2(g) yields were recorded as 98% after 45 min hydrolysis times at 45 oC, at a pH of 13.0. 99% H2(g) yields were found after 14 min hydrolysis times, at pH a pH of 13.0 at 65 oC. The maximum NaBH4 concentration and using Co NPs concentrations were kept constant at 300 mg/l and 1.5 mg/l, respectively.

Temperature-Dependent NiFeAl catalysts for efficient microwave-assisted catalytic pyrolysis of polyethylene into value-added hydrogen and carbon nanotubes

Polyolefins, comprising the majority of disposable plastics, face challenges in catalytic upcycling due to their inert saturated C(sp3)-C(sp3) bonds. This work demonstrates microwave-assisted catalytic pyrolysis, demonstrating the direct conversion of low-density polyethylene (LDPE) into valuable H2 and multi-walled carbon nanotubes (MWCNTs) over a porous ternary NiFeAl-T composite catalyst that serve as a microwave absorber. Optimizing the calcination temperature promoted metal nanoparticle dispersion, leading to enhanced catalytic performance. Specifically, lower temperatures favored metal–metal interactions, inducing porous architectures with superior microwave absorption and energy dissipation capabilities. This facilitated cleavage of C–C and C–H bonds in LDPE during microwave irradiation. An optimal NiFeAl-450 catalyst achieved a maximum H2 yield of 60.5 mmol gLDPE-1, with an H2 concentration of 85.1 vol% in gas products, alongside high-value MWCNTs. Moreover, successive recycling test displayed stable H2 and MWCNTs yields from LDPE. This work elucidates a promising pathway for upcycling plastic waste via microwave-assisted catalytic pyrolysis.

Investigations on oxygen carriers derived from natural ores or industrial solid wastes for chemical looping hydrogen generation using biomass pyrolysis gas

Chemical looping process based on multiple-step redox reactions of oxygen carriers (OCs) holds great promise for producing high purity hydrogen with inherent CO2 separation, however, there is a challenge to prepare environmental-friendly OCs with low-cost. Herein, a series of natural ores and industrial solid wastes were screened and made into Fe-based OCs for chemical looping hydrogen generation (CLHG). The results show that OCs prepared by pyrite cinder (OC-PC) feature 94.8% biomass pyrolysis gas (BPG) conversion and 94.5% CO2 concentration in OCs reduction stage. In hydrogen production stage, OC-PC achieves maximum H2 yield, 3.04 mmol g−1, which is 2∼9 times high than other OCs. The highest H2 purity is approximately 99.99%. Long term testing results indicate that OC-PC has excellent stable activity and anti-sinter ability. OCs prepared by red mud correspond to better BPG conversion (96.0%), however, the H2 yield (0.83 mmol g−1) is much lower than that of OC-PC. For OCs prepared from natural ores, they show unsatisfactory H2 production and BPG conversion compared with OC-PC. OCs prepared by ilmenite are with low specific surface area which restrains the heterogeneous reaction. The content of metal element (Mg, K, Ca) also influences the behavior of OC, which is beneficial for the fuel conversion. Moreover, the distribution of inert, anti-coking ability, oxygen vacancy also influence the sinter, H2 purity and H2 yield. Comprehensively evaluating the OCs performance, pyrite cinder is considered to be the most suitable OC raw material for CLHG.

Evaluating the role of salinity in enhanced biogas production from two-stage anaerobic digestion of food waste by zero-valent iron

Salts including NaCl are the most common food flavoring agents so they are often accumulated in food waste (FW) and have potential impact on anaerobic digestion (AD) of FW. In this study, the enhanced biogas production from two-stage anaerobic digestion (TSAD) of FW by microscale zero-valent iron (ZVI) under different salinity (3, 6, 9, and 15 g NaCl/L) was evaluated. Under salinity stress, ZVI becomes a continue-release electron donor due to the enhanced corrosion and dissolution effect and the slow-down surface passivation, further improving the performance of TSAD. Experimental results revealed that the biogas production including H2 and CH4 from TSAD with 10 g/L ZVI addition was promoted under salinity stress. The maximum H2 and CH4 yield (303.38 mL H2/g-VS and 253.84 mL CH4/g-VS) were observed at the salinity 9 g NaCl/L. Compared with that of zero salinity, they increased by 40.94% and 318.46%, respectively. Additionally, Sedimentibacter, an exoelectrogen that can participate in the direct interspecies electron transfer, also exhibited the highest relative abundance (34.96%) at the salinity 9 g NaCl/L. These findings obtained in this study might be of great importance for understanding the influence of salinity on the enhanced AD by ZVI.

Nanoparticle-assisted biohydrogen production from pretreated food industry wastewater sludge: Microbial community shifts in batch and continuous processes

Biohydrogen production from industrial waste has gained a significant attention as a sustainable energy source. In this study, the enrichment of biohydrogen production from pretreated dissolved air flotation (DAF) sludge, generated from food industry wastewater treatment plants, was investigated using SiO2@Cu-Ag dendrites core–shell nanostructure (NS). The effect of NS on the changes of the microbial community and biohydrogen yield was evaluated through batch and continuous tests. In batch mode, various nanomaterial doses were investigated with several concentrations ranging from 20 to 50 mg/L for hydrogen production using glucose as a substrate. The optimum core–shell NS amount was 40 mg/L, achieving a maximum H2 yield of 163 mL/g volatile solids (VS) compared to the control's 79 mL/g VS. However, 50 mg/L NS inhibited most bacteria in the sludge. The continuous experiment used a continuous stirring tank reactor (CSTR) with 40 mg/L SiO2@Cu-Ag core–shell NS and pretreated industrial sludge as substrate. The H2 yield increased to 115 L/kg VS compared to the control reactor's 89 L/kg VS. The gas analysis showed compositional proportions of 83 % H2, 7 % CO2, and 4.5 % methane, while the microbial community analysis indicated the development of hydrogen-producing species such as Clostridium. In conclusion, SiO2@Cu-Ag core–shell NS addition enhanced anaerobic degradation of organic matter and its conversion to biohydrogen. The selected nanomaterial can be used for an effective continuous treatment system for industrial sludge while promoting dark fermentation.

Enhancing biohydrogen production by peanut shell carrier assisted fermentation at different hydraulic retention time

The microbial immobilization and suitable hydraulic retention time (HRT) are conducive to maintain the biomass for further prompting the hydrogen production efficiency. In this study, peanut shell was employed as carriers to investigate the hydrogen production enhancement and the promotion mechanism at different HRTs with plastic pellet carrier as control. Both of the over-acid phenomenon and the operational stability decreasing occurred when HRT was shorter or longer than 6 h (HRT = 2 h, 4 h, or 8 h) in this study. When peanut shell was used as carrier, the maximum H2 yield of 1.7 L and H2 production rate of 0.58 L/L/d were obtained at HRT of 6 h, which were nearly 20 % and 15 % higher than that of plastic pellet as carriers, respectively. The hydrogen production system with peanut shell as carriers had better hydrogen production capacity and immobilized effect, since peanut shell provided a supplementary substrate for the growth and metabolism of hydrogen producing bacteria, and buffered the acidity of the system. This study provided an application for immobilization technology and the industrialization of bio-hydrogen production.

Enhanced biohydrogen production from high loads of unpretreated cattle manure by cellulolytic bacterium Caldicellulosiruptor bescii at 75 °C

Caldicellulosiruptor bescii is the most thermophilic cellulolytic bacterium capable of fermenting crystalline cellulose identified to date, and it also has a superior ability to degrade plant biomass without any pretreatment. This study is the first to assess the potential of utilizing unpretreated cattle manure (UCM) as a feedstock for hydrogen (H2) production by C. bescii at a concentration range between 2.5–50 g volatile solids (VS)/L. At 50 g VS/L UCM concentrations, H2 production ceased due to inhibition of C. bescii. To alleviate the impacts of inhibition, two strategies were adopted: (i) reduction of H2 build-up in the reactor headspace via gas sparging and (ii) adaptation of C. bescii to UCM via adaptive laboratory evolution (ALE). The former increased H2 yield by 47% compared to the control reactors, where no sparging was applied. The latter increased H2 yield by 142% compared to the control reactors inoculated by the wild type C. bescii. The UCM-adapted C. bescii demonstrated a remarkable H2 yield of 161.3 ± 1.6 mL H2/g VSadded at 15 g VS/L. This yield represents a twofold increase compared to the maximum H2 yield reported in the literature amongst fermentation studies utilizing manure as feed. At 15 g VS/L, around 73% of UCM was solubilized, and the carbon balance indicated that most of the effluent carbon was in the sugar- and acid-form. The remarkable ability of C. bescii to produce H2 from UCM under non-sterile conditions presents a significant potential for sustainable biohydrogen production from renewable feedstocks.

Ex-situ catalytic upgrading of biomass pyrolysis volatiles over thermal-decomposition products of spent lithium-ion batteries for bio-oil deoxygenation and hydrogen-rich syngas production

Spent lithium-ion batteries rich in transition metals are highly potential to catalyze the biomass pyrolysis process. This research provided insight into the performance and mechanism of ex-situ catalytic upgrading of biomass pyrolysis volatiles over the thermally pyrolyzed spent Ni–Co–Mn ternary batteries (PyNCM) for the first time. The results showed that the PyNCM exhibited high catalytic activities for the secondary decompositions of pyrolysis volatiles, resulting in 12.6% reduction on bio-oil yield and 57.5% promotion on syngas productivity. The magnetic Ni and Co compounds in PyNCM were primarily responsible for the enhanced volatile deoxygenations, and the maximum H2 yield reached 2.66 mmol g−1 biomass. Two levels of synergistic catalysis were identified: (1) the synergy among the transition metals established multiple active centers to promote the H2 selectivity; (2) the non-magnetic graphite and lithium could probably improve the dispersion and surface oxygen vacancies of nickel and cobalt to further enhance the catalytic activity.

Optimizing biohydrogen production yields by employing locally isolated thermophilic bacteria from hot springs

A climate-neutral economy is anticipated to rely heavily on hydrogen because it enables emission-free transportation, heating, and manufacturing operations. Biohydrogen can be produced from various kinds of biological waste making the interest high. However, the yield and efficiency of the processes are still challenging. This study applied Box-Behnken statistical experimental design to investigate the influence of temperature (oC), pH, and CO volume (mL) together with the amount of Fe+2, Zn+2, and Ni+2 to enhance biohydrogen production yields from thermophilic cultures, both mixed and pure cultures isolated from hot springs in Izmir, Türkiye. The maximum H2 yields were reported as 0.13 mmolH2/mmolCO for mixed cultures, and the pure culture reached 2.5 fold higher yield (0.44 mmolH2/mmolCO). Bench-scale bioreactor with a custom-design micro sparger was successfully run for 7 days (highest 0.25 mmolH2/mmol CO). This is the first report in the literature with local isolates to demonstrate the optimization of H2 yields with a comparative approach, and scale-up in a 2 L bench scale bioreactor. The viability of using novel thermophilic isolates as biohydrogen producers was successfully proven.

Well-designed bio-based waste sewage sludge (WSS) cocatalyst coupled g-C3N4 nanorods with the synergistic effect of sludge metals (M=Ni, Cu, Al, Mn) to construct ternary heterojunction for solar H2 production

A ternary heterojunction of waste sewage sludge (WSS) as a co-catalyst with sludge metals (M = Ni, Cu, Zn, Mn, and Fe) elements anchored over g-C3N4 nanorods (g-CNNR) was fabricated for photocatalytic H2 evolution under visible light. The innovative WSS enables H2 production of 25 μmol h−1 g−1 due to the presence of oxidized (Fe2O3, ZnO) and other metals to promote charge carrier separation. The g-CNNR with WSS provides good interface interaction with proficient charge carrier separation and can potentially enhance photocatalytic activity, as confirmed by standard metal elements. Using a 10% WSS/g-CNNR nanotexture, a maximum H2 yield of 195 μmol h−1 g−1 was achieved, 4.5 and 7.8 times higher than pure g-CNNR and WSS, respectively. The finding reveals that adding WSS significantly increases the photocatalytic H2 generation under visible light. This noticeable improvement was caused by the formation of heterojunction, which separated charge carriers, higher visible light absorption and synergistic effects of multiple elements in WSS which contributed to promote solar hydrogen evolution. Furthermore, the ultrasonic approach was found promising to enhance H2 evolution approximately two-fold than of bulk WSS/g-CNNR due to more light penetration and separation of charge carriers. Among the sacrificial reagents, methanol enables a higher yield of H2 with more stability in multiple cycles. The findings of this work would be beneficial for further investigation on the use of WSS as a cocatalyst and support in different energy and environment applications.

Hydrogen production from an on-board reformer for a natural gas engine: A thermodynamics study

In the present study, for an insight into the optimizing windows of comprehensive energy efficiency for open-loop system of marine NG engine and reformer, a peculiar thermodynamic equilibrium model for simulating the exhaust gas-fuel reforming process is established using equilibrium constant and experimental results. The accuracy of the model is evaluated by comparing numerical simulations with data derived from experiment of the open-loop operation system. Accordingly, the effect of engine loads and excess air (λ) as well as reformer feedstocks on maximum theoretical reforming characteristics are investigated. In addition, the energetic distribution in open-loop operation system can be clarified by the first law of thermodynamic. The results shown that fuel conversion toward H2 is highly selective due to the enhancement of reaction temperature with increasing engine loads. Especially, under 75% engine load, the maximum theoretical H2 yield reaches up to approximately 42.3% when λ = 1.4, CH4/O2 (M/O) = 1.5 and H2O/CH4 (S/M) = 2; The high λ will dilute the feed concentration of the reformer, thereby inhibiting the reforming reaction moving toward H2 production. Hence, an appropriate λ (1.4) can maximize the hydrogen production capacity of the reformer. In addition, according to the energy distribution of the open-loop system, the theoretical reforming energy efficiency of the reformer reaches a peak of 93.5% at S/M = 2 and M/O = 5. However, it can be found that M/O should be maintained above 1.5 to acquire optimal reforming energy utilization efficiency of system. Summarily, the optimal operation conditions for the reformer in open-loop operation system are confirmed: M/O = 1.5–2.5 and S/M = 1.5–2 under 75% engine load, which could fulfill efficient reforming performance.

Dark fermentative hydrogen production from cassava starch: A comprehensive evaluation of the effects of starch extrusion and enzymatic hydrolysis

Hydrolysis could be rate-limiting for the dark fermentative H2 production from cassava starch (CS) due to its semicrystalline nature. Therefore, the effects of CS extrusion and enzymatic hydrolysis on improving dark fermentation (DF) were studied. Preliminary DF experiments were conducted to investigate the effects of inoculum (sludge) heat-pretreatment, which increased H2 production from untreated-CS by over 154%. Likewise, 15 g/L starch was considered best for H2 production. Extruded-CS presented a maximum H2 yield of 1.58 mol H2/mol glucose with a 76% reduction in the fermentation adaptive phase and 43% increase in maximum H2 productivity compared to untreated-CS. Meanwhile, extruded-CS hydrolysate presented a maximum H2 yield of 1.8 mol H2/mol glucose with a 63% reduction in the fermentation adaptive phase and 18% increase in H2 productivity. A comprehensive assessment of the H2 yield, process time, production rate, and process simplification revealed extruded-CS as the most promising feedstock under the evaluated conditions.

Nanoporous oxide coating on carbon paper electrodes to enable bio-hydrogen production in microbial electrolysis cells

To counteract expensive cathodes, a single chamber microbial electrolysis cell (MEC) equipped with nanoporous oxide coating on a carbon paper electrode as a cathode was explored. The performance of the MEC was evaluated based on the chemical oxygen demand (COD) removal efficiency, catalytic activity, and hydrogen production. The obtained results indicated that nanoporous oxide coated carbon electrode with TiO2 achieved maximum H2 yield (3.0 mol H2 mol−1 acetate), followed by ZrO2 and SiO2. In contrast, the uncoated carbon electrode achieved lower hydrogen yield (0.08 mol H2 mol−1 acetate). A maximum COD removal of 82% was achieved from the carbon electrode coated with TiO2 followed by 80.5% from SiO2 and 79% from ZrO2. Additionally, based on linear sweep voltammetry, nanoporous oxide coated electrodes started H2 evolution at a lower potential than the uncoated electrode, thereby exhibiting a higher catalytic rate. This investigation showed that carbon electrodes with nanoporous coating can be one of the economical (low cost) and potential electrodes to be used as a cathode in the MEC for hydrogen production instead of expensive metallic electrodes.

Hydrogen Production from Catalytic Pyrolysis of Phenol as Tar Model Compound in Magnetic Field

Tar conversion during biomass pyrolysis is essential for hydrogen production. In this study, phenol and 10 wt.% Ni/CaO-Ca12Al14O33 were used as the tar model compound and catalyst, respectively. The purpose of the present investigation was to analyze the influence of varying magnetic field strength (ranging from 0 to 80 mT), reaction temperature (ranging from 550 to 700 °C), and carrier gas velocity (ranging from 20 to 30 mL/min) on the catalytic pyrolysis outcomes obtained from phenol. The findings indicated that the conversion rate of phenol and H2 output exhibited an increase with an escalation in magnetic field strength and reaction temperature but demonstrated a decrease with an upsurge in the carrier gas velocity. The ideal conditions for achieving the maximum phenol conversion (91%) and H2 yield (458.5 mL/g) were realized by adjusting the temperature to 650 °C, retaining the carrier gas velocity at 20 mL/min, and elevating the magnetic field intensity to 80 mT. These conditions resulted in a considerable increase in phenol conversion and H2 yield by 22.2% and 28.2%, respectively, compared with those achieved without magnetism. According to the kinetic calculations, it was indicated that the inclusion of a magnetic force had a beneficial effect on the catalytic efficacy of 10 wt.% CaO-Ca12Al14O33. Additionally, this magnetic field was observed to lower the activation energy required for the production of H2 when compared with the activation energy required during phenol catalytic pyrolysis. This consequently resulted in an enhancement of the overall efficiency of H2 production.