Optimal Hydrogen Research Articles

IoT real-time monitoring system implemented to observe sunlight-influenced methylene blue degradation by AC/HAp.

Activated carbon (AC) and hydroxyapatite (HAp) composite were successfully prepared via mechanical mixing and exhibited a crushed snack-like morphology compared to the well-defined pore structure of pure AC. The purpose of this research was to explore the potential of AC/HAp for the degradation of methylene blue (MB) dye and hydrogen production. Despite the morphological changes, AC and AC/HAp achieved a high MB degradation rate (92.75 and 82.05) % under sunlight, at a temperature of 26.24°C and pH of 4.18, and showed optimum hydrogen production (3579mol/g.h). These performances are suspected from the decrease in crystallite size and narrowed and confirmed by image processing results with RBG enhancement showing more light transmitted by the solution. Increasing in indicates the potential for improved light interaction. IoT-enabled real-time monitoring system demonstrates its efficacy in facilitating wastewater treatment and hydrogen production, offering a promising solution for aquatic ecosystem restoration.

Constructing a Z-scheme heterojunction of oxygen-deficient WO3-x and g-C3N4 for superior photocatalytic evolution of H2

Semiconductor-based photocatalytic water splitting enables the conversion of abundant solar energy to green and renewable hydrogen energy. Graphitic carbon nitride (g-C3N4) is synthesized using a straightforward method, demonstrating stable physicochemical properties and possessing an optimal bandgap, thus positioning it as a promising photocatalyst in the realm of environmental sustainability. Oxygen vacancies are extensively employed to modulate light absorption and surface properties of metal-oxide semiconductors. In this study, g-C3N4 nanosheets were coupled with oxygen-deficient tungsten trioxide (WO3-x) to form heterojunction photocatalysts (X-WOCN). Comprehensive material characterization results demonstrated that the constructed heterojunction extended the visible light absorption range, improved photogenerated electron-hole separation efficiency, and thus augmented photocatalytic activity. Notably, the optimum hydrogen evolution rate of 6 %-WOCN was enhanced by 5.4-fold compared to that of g-C3N4. Furthermore, we propose a Z-scheme heterojunction charge separation mechanism mediated by oxygen defects and support this mechanism through detection of surface-active substances •O2− and •OH. This study offers novel propositions into the function of oxygen defects in facilitating charge separation within Z-scheme heterojunction.

Step‐Directed Epitaxy of Unidirectional Hexagonal Boron Nitride on Vicinal Ge(110)

Insulating hexagonal boron nitride (hBN) films with precisely controlled thickness are ideal dielectric components to modulate various interfaces in electronic devices. To achieve this, high‐quality hBN with controlled atomic configurations must be able to form pristine interfaces with various materials in devices. However, previously reported large‐scale hBN films with uniform thickness either are polycrystalline or are not suitable for atomically clean assembly via mechanical exfoliation, limiting their applications in device technology. Herein, the large‐scale growth of monolayer (ML) single crystalline hBN films on Ge(110) substrates by using chemical vapor deposition is reported. Vicinal Ge(110) substrates are used for the step‐directed epitaxial growth of hBN, where Ge atomic steps act as the hBN nucleation sites, guiding the unidirectional alignments of multiple hBN domains. Density functional theory calculations reveal that the optimum hydrogen passivations on both hBN edges and Ge surfaces enable the epitaxial coupling between hBN and the Ge step edges and the single crystallinity of the final hBN films. Using epitaxially grown ML hBN films, a few hBN films with controlled stacking orders and pristine interfaces through a layer‐by‐layer assembly process are fabricated. These films function as high‐quality dielectrics to enhance carrier transport in graphene and MoS2 channels.

Multi-variable optimization of a geothermal power plant integrated with water electrolyzer and methanol production

Renewable energy-based routes for methanol generation are recognized as essential strategies for eco-friendly energy conversion. Thus, the current study focuses on developing an innovative combined energy system for methanol production using direct carbon dioxide hydrogenation powered by geothermal energy. This is important because it addresses the need for sustainable and environmentally friendly methods of methanol production while also harnessing the potential of geothermal energy as a renewable resource. Therefore, in order to achieve multigeneration energy production, this work introduces and optimizes a novel configuration that benefits from an innovative heat design process. This configuration integrates an organic Rankine cycle, a single-flash geothermal power plant, an ammonia-water absorption chiller, a proton exchange membrane electrolyzer, and a methanol generation unit. Using the Aspen HYSYS tool, the multigeneration energy system is modeled and analyzed. As a result, the system is assessed using energy, exergetic, environmental, and economic evaluations. Furthermore, performance evaluations are carried out in the following modes: single generation, multigeneration, cooling, heat and power generation, and cooling. Furthermore, a genetic algorithm is employed to optimize the system in terms of economy and exergy. The energy and exergy efficiency are determined to be 32.57 % and 76.3 %, respectively, under the base case results. Furthermore, the rate of overall costs is 377.38 $/h. Furthermore, the precise output of carbon dioxide is −0.043 kg/kWh. The optimal unit cost and exergy efficiency for all items, taking into account the optimization scenario, are 3.34/GJ and 78.35 %, respectively. In addition, the optimum carbon dioxide and hydrogen rates for methanol generation are 92.49 mol/h and 200.51 mol/h, respectively.

A comprehensive analysis of a compact-sized methanol cracking unit for hydrogen production

Methanol is recognized as source of hydrogen production, making it a suitable fuel for sustainable development. However, hydrogen production methods remain a concern. An experimental setup and a simulation model in Aspen Plus, incorporating an evaporator and cracker, are developed for hydrogen production. The effects of dimensional parameters, including the length and diameter of the cracker, temperature, and pressure in the presence of the catalyst SCST- 403, on hydrogen production and methanol conversion via thermal catalytic cracking have not been discussed yet. The experimental results show that the optimum hydrogen mole fraction exceeds 0.52, and methanol conversion exceeds 60% at a length of 2.83 m, diameter of 4.07 mm, temperature of 500 °C, and pressure of 2.7 MPa. The investigation is extended to redesign the cracker unit using Aspen Plus based on reaction kinetics. Simulations on various dimensions, temperatures, and pressures reveal that, after redesigning, the optimum hydrogen mole fraction exceeds 0.60, and methanol conversion reaches 85% at a length of 4.5 m, diameter of 5.2 mm, temperature of 500 °C, and pressure of 3 MPa.

Membrane-electrode junction properties for optimum potentiometric hydrogen sensor response

Membrane-electrode junction properties for optimum potentiometric hydrogen sensor response

Process Integration of Hydrogen Production Using Steam Gasification and Water-Gas Shift Reactions: A Case of Response Surface Method and Machine Learning Techniques

An equilibrium-based steady-state simulator model that predicts and optimizes hydrogen production from steam gasification of biomass is developed using ASPEN Plus software and artificial intelligence techniques. Corn cob’s chemical composition was characterized to ensure the biomass used as a gasifier and with potential for production of hydrogen. Artificial intelligence is used to examine the effects of the significant input variables on response variables, such as hydrogen mole fraction and hydrogen energy content. Optimizing the steam-gasification process using response surface methodology (RSM) considering a variety of biomass-steam ratios was carried out to achieve the best results. Hydrogen yield and the impact of main operating parameters were considered. A maximum hydrogen concentration is found in the gasifier and water-gas shift (WGS) reactor at the highest steam-to-biomass (S/B) ratio and the lowest WGS reaction temperature, while the gasification temperature has an optimum value. ANFIS was used to predict hydrogen of mole fraction, 0.5045 with the input parameters of S/B ratio of 2.449 and reactor pressure and temperature of 1 bar and 848°C, respectively. With the steam-gasification model operating at temperature (850°C), pressure (1 bar), and S/B ratio of 2.0, an ASPEN simulator achieved a maximum of 0.5862 mole fraction of hydrogen, while RSM gave an increase of 19.0% optimum hydrogen produced over the ANFIS prediction with the input parameters of S/B ratio of 1.053 and reactor pressure and temperature of 1 bar and 850°C, respectively. Varying the gasifier temperature and S/B ratio have, on the other hand, a crucial effect on the gasification process with artificial intelligence as a unique tool for process evaluation, prediction, and optimization to increase a significant impact on the products especially hydrogen.

Cu-MOF modified ZnIn2S4 nanosheet composite catalyst for photocatalytic hydrogen production

In the realm of photocatalysis, the creation of clean and pollution-free composite material catalysts is critical. Electrostatic self-assembly techniques were used in this study to construct ZnIn2S4 nanosheets onto the surface of Cu-MOF, culminating in the development of a unique Cu-MOF/ZnIn2S4 composite catalyst. Cu-MOF was shown to have a strong interface impact with ZnIn2S4, which resulted in a large increase in the number of active sites and, consequently, the efficiency of hydrogen generation. This was demonstrated by a number of parameters. The Cu-MOF/ZnIn2S4-10 composite material's optimum hydrogen evolution rate was 0.3 mmol h−1g−1, which was 2.14 times larger than that of pure ZnIn2S4 nanosheets (0.14 mmol h−1g−1). Furthermore, the development of Cu-MOF/ZnIn2S4 heterojunctions considerably improved ZnIn2S4's deficiencies in photocatalytic hydrogen production, increasing charge separation rates and providing a viable approach to improve ZnIn2S4's hydrogen production efficiency.

Efficient phosphate and hydrogen recovery from sludge fermentation liquid by sacrificial iron anode in electro-fermentation system

Electro-fermentation (EF) has been extensively studied for recovering hydrogen and phosphorus from waste activated sludge (WAS), while was limited for the further application due to the low hydrogen yield and phosphorus recovery efficiency. This study proposed an efficient strategy for hydrogen and vivianite recovery from the simulated sludge fermentation liquid by sacrificial iron anode in EF. The optimum hydrogen productivity and the utilization efficiency of short chain fatty acids (SCFAs) reached 45.2 mmol/g COD and 77.6% at 5 d in pH 8. Phosphate removal efficiency achieved at 90.8% at 2 d and the high crystallinity and weight percentage of vivianite (84.8%) was obtained. The functional microbes, i.e., anaerobic fermentative bacteria, electrochemical active bacteria, homo-acetogens and iron-reducing bacteria were highly enriched and the inherent interaction between the microbial consortia and environmental variables was thoroughly explored. This work may provide a theoretical basis for energy/resource recovery from WAS in the further implementation.

Municipal sewage sludge dewatering performance enhancement by ultrasonic cavitation and advanced oxidation: A case study.

The number of published literature on the effect of ultrasonic cavitation and advanced oxidation pretreatment on the dewatering performance of anaerobically digested sludge is very limited. This study aims at determining the optimum operating conditions of large-scale filtering centrifuges in wastewater treatment plants. The optimum dose of hydrogen peroxide, ultrasonic power, ultrasonic duration, ultrasonic pulse and particle size distribution for improved dewatering performance were determined in this study. In addition, shear stress-shear rate and viscosity-shear rate rheograms were developed to show the rheological flow properties for varying ultrasonic power and treatment duration. Optimum sonication power, time, pulse and amplitude were determined to be 14 W, 1 min, 55/5 and 20%, respectively. At a pH of 6.8, the optimum concentration of hydrogen peroxide was found to be 43.5 g/L. The optimum hydrogen peroxide dose in the combined conditioning experiments was determined to be 500 mg/L at a pH of 3. Under these optimum conditions, capillary suction time was reduced significantly by 71.1%. This study helps to reduce polymer consumption and provides the optimum pretreatment and dewatering operating conditions, and better monitoring and control in the dewatering unit has significant impact in the overall economy of wastewater treatment plants.

Surface Charge Effects for the Hydrogen Evolution Reaction on Pt(111) Using a Modified Grand-Canonical Potential Kinetics Method.

Surface charges of catalysts have important influences on the thermodynamics and kinetics of electrochemical reactions. Herein, we develop a modified version of the grand-canonical potential kinetics (GCP-K) method based on density functional theory (DFT) calculations to explore the effect of surface charges on reaction thermodynamics and kinetics. Using the hydrogen evolution reaction (HER) on the Pt(111) surface as an example, we show how to track the change of surface charge in a reaction and how to analyze its influence on the kinetics. Grand-canonical calculations demonstrate that the optimum hydrogen adsorption energy on Pt under the standard hydrogen electrode condition (SHE) is around -0.2 eV, rather than 0 eV established under the canonical ensemble, due to the high density of surface negative charges. By separating the surface charges that can freely exchange with the external electron reservoir, we obtain a Tafel barrier that is in good agreement with the experimental result. During the Tafel reaction, the net electron inflow into the catalyst leads to a stabilization of canonical energy and a destabilization of the charge-dependent grand-canonical component. This study provides a practical method for obtaining accurate grand-canonical reaction energetics and analyzing the surface charge induced changes.

Experimental investigation on hydrogen transfer in coupled metal hydride reactors for multistage hydrogen purification application

Three stage metal hydride hydrogen separation system was tested, wherein each stage was configured with 1.2 kg of LaNi4.7Al0.3, LaNi5 and La0.9Ce0.1Ni5, placed in descending order of their equilibrium bed pressure respectively as R1 (La0.9Ce0.1Ni5) > R2 (LaNi5) > R3 (LaNi4.7Al0.3). Hydrogen absorption capacity obtained for R1, R2 and R3 were 15.91 g, 15.93 g and 16.02 g respectively for 3rd activation cycle, performed at 30 bar and 25 °C. For coupled reactor operation, optimum hydrogen transfer was for desorbing reactor at 90 °C and absorbing reactor at 20 °C, which was 12.31 g for R1 to R2 in 350 s, 13.33 g for R2 to R3 in 300 s and 13.38 g for R1 to R2 in 280 s, constituting to 1.03, 1.11 and 1.12 wt% of hydrogen storage respectively. Further, the system was tested for hydrogen purification, wherein inlet sample with 80% impurity (18% Ar, 20% CO2, 20% N2, 20% CH4 and 2% CO) and 20% H2 was used for purification study. According to Thermal Conductivity Detector (TCD) results, the system delivered 91.54%, 99.996% and 99.9999% pure hydrogen respectively for stage 1, stage 2 and stage 3 purification. The system works within low temperature range of 20–90 °C.

Numerical analysis on ammonia decomposition for hydrogen production in a membrane reactor assisted by a parabolic trough solar collector

Ammonia (NH3) has emerged as a promising hydrogen storage carrier due to its considerable hydrogen storage density, storage and transportation convenience, and zero carbon emissions during endothermic decomposition. By utilizing a parabolic trough solar collector to provide heat and integrating NH3 decomposition with a membrane reactor, a clean and sustainable method of hydrogen production can be achieved. This paper establishes a comprehensive numerical model for NH3 decomposition within a parabolic trough solar receiver/membrane reactor (PTSMR). The model incorporates heat and mass transfer in porous catalyst beds, membrane permeation, and reaction dynamics to accurately capture the intricate phenomena under actual operating conditions. Special attention is paid to the influences of inlet temperature, flow rate, flow pattern, and reaction pressure on NH3 conversion and hydrogen recovery. The results demonstrate that the temperature distribution within the PTSMR exhibits non-uniformity, and the temperature at the bottom is always higher than that at the top, especially at the outlet, where the temperature difference is more than 100K. The NH3 conversion rate in counterflow is higher than that in parallel flow, while the hydrogen recovery rate in parallel flow is higher due to the reverse permeation of hydrogen in counterflow. For a 2-mm-thickness catalyst bed, the addition of membranes increases NH3 conversion rate by 9% at a reaction pressure of 5 bar, compared to a 3% increase for an 8-mm-thickness catalyst bed. The PTSMR with a 2-mm-thickness catalyst bed obtains the optimum hydrogen yield rate.

Catalytic gasification of municipal solid waste using eggshell-derived CaO catalyst: An investigation of optimum H2 production, production distribution, and tar compounds

This study reports the optimum hydrogen (H2) production from municipal solid waste (MSW) via waste eggshell derived-CaO catalyst through gasification technology. The response surface model was applied to design the experiments and the data validation. Results showed that CaO catalyst had a better performance that enhanced 15 mol% more H2 production than non-catalytic gasification by mainly involving reaction temperature and catalyst loading as the critical parameters. Tar content was efficiently declined from 11.34 wt. % to 4.7 , wt. %, which ultimately elevated the H2 and syngas from 33.95 mol% to 51.27 mol% and 74.05 to 83.4674.05–83.46 wt. %, respectively. The model showed a strong interaction among the statistical parameters verified through the regression values; R2 = 0.990, P-value = 0.000005, respectively. Scanning electron microscopy, X-ray diffraction, and Brunauer-Emmett-Teller techniques investigated the catalyst's structure hence; presented comparable results. From tar analysis, the aromatics were found as the dominant family followed by polycyclic aromatic, phenyls, aliphatic, aromatic heterocyclic, polycyclic, and aromatic ketones. Optimum H2 production of 51.27 mol% (with H2/CO ratio 2.82, LHV 9.47 MJ/Nm3, and H2 yield 22.74 mol kg-MSW−1) was produced which can be a better alternative to depleting fossil fuels and utilized for liquid fuel manufacturing and power generation.

Experimental and CFD analysis on the impact of hydrogen as fuel on the behavior of a passenger car gasoline direct injection engine

The influence of hydrogen induction on the behavior of a Multi cylinder automotive GDI (Gasoline Direct Injection) engine was studied. An advanced 3D engine simulation was done and validated with experimentally acquired 5% and 10% hydrogen mass coupled with gasoline direct injection. Comparing to the pure gasoline mode, introducing hydrogen showed considerable improvement in engine's BTE (brake thermal efficiency) at all power outputs. The maximum BTE was observed as 27.2%, 30% and 32.5 respectively with pure gasoline, 5% and 10% hydrogen mass shares at the engine's power output of 21 kW. At all power outputs, hydrogen admission was shown to produce a smaller amount hydrocarbon (HC) and carbon monoxide (CO) emissions than pure gasoline operation. At 21 kW engine power the HC was noted as 3360, 2400 and 2050 ppm respectively with Pure Gasoline, 5% and 10% hydrogen mass shares. CFD results on the HC and CO emissions indicated a strong agreement with the experimental results. NOx emission was noted as higher with hydrogen addition (80 and 100 ppm respectively with 5% and 10% hydrogen mass shares) as compared to 60 ppm with pure gasoline mode. High temperature of the gas supported by the CFD due to the rapid combustion of hydrogen was noted as the reason for the higher NOx emissions with hydrogen addition. CFD results on cylinder pressure and HRR matched very well with the experimental results. A small amount of hydrogen added to the gasoline as a fuel supplement might greatly improve BTE while lowering HC and CO emissions. The recommended optimum hydrogen mass share is 10% for the best performance of the above said engine without any modification in engine design.

Rapid microwave preparation of CuS/ZnCdS Z-scheme heterojunction for efficient photocatalytic hydrogen evolution

Low-cost transition metal sulfides have been shown to be ideal candidates for photocatalytic hydrogen evolution. However, most preparation processes have long reaction times and high energy consumption. In this work, CuS/ZnCdS heterojunction was prepared by a rapid and energy-saving microwave method. It was characterized by SEM, TEM, XRD, XPS, and photoelectrochemical tests. The results showed that CuS was successfully loaded with ZnCdS and did not alter the intrinsic structure of ZnCdS. It not only improved the light absorption efficiency, but lowered the position of the conduction band and reduced the forbidden band width. The optimum photocatalytic hydrogen evolution rate of CuS/ZnCdS could get 7.58 mmol g−1 h−1 and the AQE was 10.07% at 420 nm. The enhanced photocatalytic activity can be attributed to the construction of Z-scheme heterojunction to promote the separation and transfer of photogenerated charges. This work provides a valuable route to explore high quality ZnCdS based photocatalysts using a fast, low-cost microwave technique.

Nickel-iron doped on granular activated carbon for efficient immobilization in biohydrogen production

Nickel-iron doped granular activated carbon (GAC-N) was used to enhance immobilization in biohydrogen production. The effect of the sludge ratio to GAC-N, ranged 1:0.5–4, was studied. The optimum hydrogen yield (HY) of 1.64 ± 0.04 mol H2/mol sugar consumed and hydrogen production rate (HPR) of 45.67 ± 1.00 ml H2/L.h was achieved at a ratio of 1:1. Immobilization study was performed at 2 d HRT with a stable HY of 2.94 ± 0.16 mol H2/mol sugar consumed (HPR of 83.10 ± 4.61 ml H2/L.h), shorten biohydrogen production from 66 d to 26 d, incrementing HY by 57.30 %. The Monod model resulted in the optimum initial sugar, maximum specific growth rate, specific growth rate, and cell growth saturation coefficient at 20 g/L, 2.05 h−1, 1.98 h−1 and 6.96 g/L, respectively. The dominant bacteria identified was Thermoanaerobacterium spp. The GAC-N showed potential as a medium for immobilization to improve biohydrogen production.

Photostimulated Covalent Linkage Transformation Isomerizing Covalent Organic Frameworks for Improved Photocatalytic Performances.

Covalent organic frameworks (COFs) offer a desirable platform to explore multichoromophoric arrays for photocatalytic conversion. Symmetric arrangement of choromophoric modules over π-extended frameworks enhances exciton delocalization while impairing excitation density and accordingly photochemical reactivity. Herein, a photoisomerization-driven strategy is proposed to break the excited-state symmetry of ketoenamine-linked COFs with multichoromophoric arrays. Incorporating electron-withdrawing benzothiadiazole facilitates the ultrafast excited-state intramolecular proton transfer (ESIPT) from enamine to keto within 140 fs, resulting in partially enolized COF isomers. The hybrid linkages containing imine and enamine bonds at the node of framework alter the symmetry of electronic structure and enforce the photoinduced charge separation. Increasing the imine-to-enamine ratio further promotes the electron transferred number in a long range, thereby affording the optimum photocatalytic hydrogen evolution rate. This work put forward an ESIPT-induced photoisomerization to build a symmetry-breaking COF with weakened exciton effect and enhanced photochemical reactivity.

Electronic optimization of heterostructured MoS2/Ni3S2 by P doping as bifunctional electrocatalysts for water splitting

MoS2 is an excellent catalyst for hydrogen evolution reaction (HER) because of its close proximity to the optimum hydrogen adsorption free energy (ΔGH*). However, poor oxygen evolution reaction (OER) intrinsic activity, insufficient active sites, and poor conductivity hinder its application as a bifunctional electrocatalyst. Here, Ni3S2 is combined with MoS2 forming MoS2/Ni3S2 heterostructure due to its intrinsic OER activity and P is chosen as an anion dopant to optimize ΔGH* due to its near-thermoneutral H adsorption to explore the bifunctional performance of MoS2 based nanocomposites. The electronic configurations of Mo, Ni, and S on the interface are modulated by P doping, which optimizes their adsorption/desorption ability of intermediates. The synergistic effect of anion doping and heterostructure induces excellent catalytic activity in P40-MoS2/Ni3S2–5 (Mo to S molar ratio of 1:5 and 40 mg P dopants) with overpotentials of 142 mV for HER and 278 mV for OER at 100 mA cm−2 in 1.0 M KOH solution. The voltage of overall water splitting is 1.76 V using P40-MoS2/Ni3S2–5 as the anode and cathode. This work elucidates a method of optimizing the electronic structure by doping P anion in heterointerface, providing an avenue to boost the catalytic activity of non-noble metal-based catalysts.

Performance enhancement and emissions reduction of ethanol‐fueled spark ignition engine with hydrogen

AbstractThis study deals with the effect of hydrogen on the performance, combustion and regulated [carbon monoxide (CO), non‐methane hydrocarbons (NMHC), nitric oxide (NO), nitrogen dioxide (NO2)] and unregulated [nitrous oxide (N2O), ethanol, ethene, acetaldehyde, methanol] emissions of a spark ignition engine fueled with ethanol (E100). The engine was operated at a constant torque of 5.5 Nm and various speeds of 3500, 3800 and 4000 rpm, and both fuels (ethanol and hydrogen) were independently injected into the intake manifold of the engine during the suction stroke. The optimum hydrogen energy share at all speeds was 15% based on the combustion stability compared with base ethanol. The brake thermal efficiency with E100 at an engine speed of 4000 rpm increased from 14.4 to 15%, with a 15% hydrogen energy share (15% HES)‐E100. The emissions such as CO, NMHC, unburned ethanol, ethene and acetaldehyde decreased significantly with the optimum HES‐E100 compared with E100. However, the NO, NO2 and N2O emissions increased with hydrogen. Hydrogen addition to an ethanol‐fueled spark ignition engine could significantly reduce carbonaceous emissions along with improving energy efficiency.