Efficient Hydrogen Production Research Articles

Pilot microbial electrolysis cell closes the hydrogen loop for hydrothermal wet waste conversion to jet fuel

The global shift toward net-zero emissions necessitates resource recovery from wet waste. In this study, we demonstrate the first feasibility of combining pilot-scale microbial electrolytic cells (MECs) with hydrothermal liquefaction (HTL) for simultaneous post-hydrothermal liquefaction wastewater (PHW) treatment and efficient hydrogen (H₂) production to meet biocrude upgrading requirements. Long-term single reactor operation revealed that fixed anode potential enabled rapid startup, and low catholyte pH and high salinity were effective in suppression of cathodic methanogenesis and acetogenesis – resulting in high current density of 16.6 A m−2 and 9.3 A m−2 when feeding synthetic wastewater and PHW respectively. Additionally, the anode biofilm exhibited spatial variations in response to local environmental conditions. Onsite parallel or serial operations of multiple MECs showed good performance using actual PHW with a record-high H2 production rate of 0.5 L LR day−1 for MEC over 10 liters scale, and the optimal chemical oxygen demand (COD)-to-H2 yield reached 0.127 kg-H2 per kg-COD, supporting a self-sufficient, closed-loop upgrade to jet fuel.

Trinuclear iron-oxo cocatalyst regulating new electron transfer pathway in Pt loaded bismuth oxychloride for efficient photocatalytic hydrogen production

BiOCl, a traditional p-type semiconductor, finds extensive application in photocatalytic oxidation and degradation, whereas it is less common in photocatalytic water splitting and hydrogen production. Here, the photocatalytic hydrogen production performance of black BiOCl has been examined by the introduction of noble metal platinum and cocatalyst trinuclear iron-oxo cluster. During the 5-h photocatalytic process, the established system significantly augments the hydrogen production efficiency of black BiOCl by an estimated factor of 8.53. Under illumination, trinuclear iron-oxo clusters provide electron recombination with holes in the valence band of the catalyst, thereby increasing the utilization of photogenerated electrons. Additionally, since the specific energy level structure has a significant impact on the cocatalyst function, trinuclear iron-oxo clusters can be suitable in a variety of photocatalytic systems. This new endeavor might present creative design approaches and low-cost cocatalyst alternatives for the photocatalytic hydrogen evolution from the water splitting of conventional p-type semiconductor materials.

Photocatalytic activity of molybdenum-doped LOS- zeolite for efficient dye degradation and hydrogen production

This research investigates the synthesis and application of Losod-zeolite (LOS-Z), a crystalline hydrated sodium aluminosilicate (Na12Al12Si12O48.xH2O) as a potential photocatalyst for dye degradation and H2 production from dye-degraded water. The photocatalytic properties are enhanced by impregnating molybdenum (Mo) into LOS-Z (Mo@LOS-Z). XRD, FTIR, SEM, EDX, and elemental mapping were used to study the physicochemical properties of synthesized materials while UV–vis and PL were employed to explore the optoelectronic properties. The photocatalytic activities for dye degradation and H2 production were evaluated using methylene blue (MB) under visible light irradiation. An enhancement in the efficiency of dye degradation (56%–82%) and H2 production rate was demonstrated due to the competitive photocatalytic performance of 10% Mo@LOS-Z compared to the pristine LOS-Z and CFA-BFA blend. It exhibited 2.5 times higher (∼1200 μmol g−1h−1) H2 production than the LOS-Z (∼480 μmol g−1h−1) due to the synergistic effects of narrowed band gap and recombination rate. This study could pave the way forward into the synthesis of waste-derived photocatalysts for efficient dye degradation and H2 production.

Hydrogen-Electrodialysis with Bipolar Membrane (H-EDBM): First experiments and preliminary economic evaluation

In the present work Electrodialysis with Bipolar Membranes (EDBM) for brine valorisation is for the first time investigated for the simultaneous production of hydrogen and chemicals. EDBM allows current densities one order of magnitude higher than ED and RED electro-membrane processes, making the technology more attractive to the hydrogen market. In this work, an experimental campaign with the Hydrogen-EDBM (H-EDBM) was conducted for the first time, investigating different configurations consisting of different end-membranes for the electrode compartments. The results showed 98 % ±2 % faradic efficiency for hydrogen production, with a productivity of up to 18.4 mol h−1 m−2 at the current density of 1000 A m−2. In addition, the Bipolar Membranes allow the simultaneous production of chemicals such as NaOH, for which a Current Efficiency of 96 % and a Specific Energy Consumptions (SECs) of 1.78 kWh kgNaOH−1 were obtained. Eventually, the research was completed with a preliminary economic analysis combining the different operations and costs of the tested configurations in order to identify the optimum of the process. The Levelized Costs Of Hydrogen (LCOH) and of NaOH (LCONaOH) were used as performance parameters. The minimum LCONaOH of 0.13 € kgNaOH−1 and LCOH of 2.4 € kgH2−1 were found when bipolar membranes are used as end-membranes and the unit is coupled with onshore wind plant, identifying this configuration as the most promising. Collected results show a great potential for the H-EDBM, thus fully justifying future more in-depth analyses.

Bicontinuous nickel/tin oxide films with enhanced photoelectrochemical hydrogen production efficiency

Self-assembled bicontinuous NiO:SnO2 films are proposed for enhanced photoelectrochemical hydrogen production efficiency due to their high interface-to-volume ratio and three-dimensional interconnectivity. The X-ray diffraction confirms the superior crystallinity of the bicontinuous NiO:SnO2 films. Bicontinuous NiO:SnO2 films reveal a heterostructure of mixed NiO and SnO2 phases, where the NiO phase exhibits the distribution of small grains, whereas the SnO2 phase exhibits large agglomerates of SnO2 crystals embedded in the NiO structure. The bicontinuous NiO:SnO2 films exhibit lower bandgap energy and higher electrical conductivity compared to pure NiO and pure SnO2 films. The photoresponsivity of the bicontinuous oxide films is higher than pure NiO and pure SnO2 films. These results imply the presence of strong charge interactions at the three-dimensional interfaces in bicontinuous NiO:SnO2 films. The hydrogen revolution reaction analysis confirms that the bicontinuous NiO:SnO2 films exhibit higher photoelectrocatalyst hydrogen production activity compared to pure NiO and pure SnO2 films.

Nickel doped enhanced LaFeO3 catalytic cracking of tar for hydrogen production

The transformation of biomass into green energy was pivotal for sustainable development, yet the efficient conversion of biomass-derived tar into hydrogen-rich syngas remained a significant challenge. This study addressed the catalytic demand for hydrogen production from tar, focusing on the development of LaNixFe1-xO3 perovskites as catalysts. A series of LaNixFe1-xO3 perovskites with varying nickel doping levels (x=0, 0.25, 0.5, 0.75, 1) were synthesized to evaluate their catalytic performance in converting toluene, a representative tar component, into hydrogen. The LaNi0.5Fe0.5O3 catalyst demonstrated the highest hydrogen yield (14.5L/6h) and volume percentage (82.9V/V%), highlighting the optimal nickel doping level for enhancing hydrogen production. The hydrogen production performance of LaNixFe1-xO3 was significantly affected by nickel doping. In particular, a small amount of nickel doping can significantly enhance the hydrogen production capacity of LaFeO3 and maintain good reaction stability. The enhanced performance was attributed to the high oxygen storage capacity of perovskite, which facilitated the removal of surface carbon and promotes the methanation reaction. Notably, the total content of defect oxygen and surface adsorbed oxygen/hydroxyl groups significantly impacted the hydrogen production efficiency. These findings indicated that LaNi0.5Fe0.5O3 was an effective catalyst for converting biomass-derived tar into hydrogen-rich syngas, offering a promising solution to the catalytic demand in the hydrogen production system.

Dynamic Simulation and Performance Analysis of Alkaline Water Electrolyzers for Renewable Energy-Powered Hydrogen Production

This paper presents a comprehensive study on the dynamic simulation modeling of alkaline water electrolyzers. Detailed experimental testing and characteristic analysis reveal that alkaline water electrolyzers have long startup times, rapid dynamic responses, and poor dynamic stability. These characteristics are critical for the development of accurate models and effective strategies. A dynamic simulation model was established in MATLAB R2022b and Simulink, enabling standalone simulation operation and module encapsulation. This model facilitates the construction of hydrogen production clusters and serves as a foundational tool for system strategy research. Simulations of rated current loading and unloading for four electrolyzers over 6 h showed significant differences in startup and operation. Key parameters such as cell voltage, maximum loadable power, hydrogen production efficiency, and energy consumption were analyzed. Temperature simulations indicated significant differences in thermal equilibrium points and cooling modes among the electrolyzers, as determined by structural design and cooling system efficiency. These findings highlight the need for efficiency improvements in high-current density electrolyzers. Overall, the model effectively represents commercial electrolyzer characteristics and offers a reliable tool for future research on control strategies for adapting hydrogen production systems to renewable energy power fluctuations, laying a solid foundation for the optimization of electrolyzer design and operation strategies.

Plasma Induced Atomic-Scale Soldering Enhanced Efficiency and Stability of Electrocatalysts for Ampere-Level Current Density Water Splitting.

Industrial water electrolysis typically operates at high current densities, the efficiency and stability of catalysts are greatly influenced by mass transport processes and adhesion with substrates. The core scientific issues revolve around reducing transport overpotential losses and enhancing catalyst-substrate binding to ensure long-term performance. Herein, vertical Ni-Co-P is synthesized and employed plasma treatment for dual modification of its surface and interface with the substrate. The (N)Ni-Co-P/Ni3N cathode exhibits an ultra-low overpotential of 421 mV at 4000 mA cm-2, and the non-noble metal system only requires a voltage of 1.85 V to reach 1000 mA cm-2. When integrated into an anion exchange membrane (AEM) electrolyzer, it can operate stably for >300 h at 500 mA cm-2. Under natural light, the solar-driven AEM electrolyzer operates at a current density up to 1585 mA cm-2 with a solar-to-hydrogen efficiency (SHT) of 9.08%. Density functional theory (DFT) calculations reveal that plasma modification leads to an "atomic-scale soldering" effect, where the Ni3N strong coupling with the Co increases free charge density, simultaneously enhancing stability and conductivity. This research offers a promising avenue for optimizing ampere-level current density water splitting, paving the way for efficient and sustainable industrial hydrogen production.

Development of integrated thermally autonomous reformed methanol-proton exchange membrane fuel cell system

This paper presents a novel thermally autonomous reformed methanol fuel cell (RMFC) system for highly efficient hydrogen production and power generation by integrating a self-heating methanol steam reforming (MSR) microreactor and a high temperature proton exchange membrane fuel cell (HT-PEMFC). The RMFC system would exhibit significant potential for portable use due to its high energy efficiency, compact size and long lifetime. The structural design of the RMFC system including MSR microreactor and HT-PEMFC are studied, and a work flow is developed to enable the startup and stable power output of the system. After that, the microreactor and HT-PEMFC are fabricated, and then integrated to develop the system. Experimental testing results showed that the microreactor can produce a maximum reformate gas of 541 ml/min with a methanol conversion larger than 93.8 %., while maintaining the carbon monoxide concentration below 2 %. The RMFC system can start up within 17 min, the temperature fluctuation is lower than 6.28 % and the maximum output power can reach up to 32.9 W. As for a conservatively designed rating power of 25 W, the calculated energy conversion efficiency of the system can reach about 28.5 %, with good stability during long-term operations.

Chiral Pd(II) Nanofiber Promoting Electron Transfer of g-C3N4 for Efficient Photocatalytic Hydrogen Production.

The rapid transfer and separation of photogenerated electrons is very important for the improvement of photocatalytic efficiency. Here, chiral induced spin selectivity effect (CISS effect) was developed to accelerate electron transfer for efficient photocatalytic hydrogen production. A chiral and achiral racemic supramolecular Pd(II) complex nanofiber was fabricated via supramolecular self-assembly of chiral L-Py or its racemes with Pd(II) and used to modify carbon nitride (g-C3N4). The obtained chiral photocatalyst L-Py-Pd/g-C3N4-4 and achiral photocatalyst Rac-Pd/g-C3N4-4, show enhanced photocatalytic activities with hydrogen evolution rates of 2476 and 1339 μmol g-1 h-1, respectively, while that of pure g-C3N4 is 30.5 μmol g-1 h-1. Chiral photocatalyst has 85% higher activity than achiral one and is 82.5-fold of pure g-C3N4, due to better suppression of the recombination of photogenerated electron-hole pairs in the interface of g-C3N4 contact with chiral molecule. Spectral tests and photoelectrochemical tests proved that the chiral supramolecular Pd(II) complex can act both as an electron spin filter and hydrogen reduction catalytic center to enhance photocatalytic efficiency. This work offers a new route to facilitate electron transfer by the CISS effect for photocatalytic hydrogen evolution.

Rational construction of ZnIn2S4/Co3Se4 with boosted photocatalytic hydrogen production through cooperate with S-scheme heterojunction and photothermal effect

The rational design of excellent visible light photocatalysts that efficiently utilize the solar spectrum is urgently needed. In this work, ZnIn2S4 (ZIS) and Co3Se4 (CS) were coupled by a multistep process involving simple ultrasonic self-assembly and calcination to form ZnIn2S4/Co3Se4 (ZIS/CS) photocatalysts with synergistic S-scheme heterojunctions and photothermal effects, which realized efficient photocatalytic hydrogen (H2) production with optimal H2 yield of 2.46 mmol h−1 g−1, superior to pure ZIS (0.47 mmol h−1 g−1) by a factor of 5.23. The excellent cyclic stability and wide environmental adaptability to the ionic environment of water of ZIS/CS were proved. The positive impaction of photothermal effect on the H2 yield of ZIS/CS was investigated and confirmed by the temperature change of photocatalysts powder or photocatalytic system under light irradiation. In addition, based on a series of characterization analyses and first-principle simulation calculations, a charge transfer pathway for ZIS/CS S-scheme heterojunctions was proposed. This work provides valuable ideas and feasible research methods for the design of stable and practical photocatalysts.

Fe2NiSe4 Nanowires Array for Highly Efficient Electrochemical H2S Splitting and Simultaneous Energy-Saving H2 Production

The electrochemical removal of abundant and toxic H2S from highly sour reservoirs has emerged as a promising method for hydrogen production and desulfurization. Nevertheless, the ineffectiveness and instability of current electrocatalysts have impeded further utilization of H2S. In this communication, we introduce a robust array of Fe2NiSe4 nanowires synthesized in situ on a FeNi3 foam (Fe2NiSe4/FeNi3) via hydrothermal treatment. This array acts as an active electrocatalyst for ambient H2S splitting. It offers numerous exposed active sites and a rapid electron transport channel, significantly enhancing charge transport rates. As an electrode material, Fe2NiSe4/FeNi3 displays remarkable electrocatalytic efficiency for both sulfide oxidation and hydrogen evolution reactions. This bifunctional electrode achieves efficient electrochemical H2S splitting at a low potential of 440 mV to reach a current density of 100 mA∙cm−2, with a faradaic efficiency for hydrogen production of approximately 98%. These findings highlight its significant potential for desulfurization and energy-efficient hydrogen generation.

Carbon cloth-based meteorite-like Co–CuS/MoS2 heterostructure for efficient water electrolysis

Developing low-cost, high-efficiency electrocatalysts is critically important for efficient hydrogen production. In this study, a novel electrocatalyst, Co–CuS/MoS2 nanocomposite, was successfully synthesized via ion exchange on carbon cloth using Evans-Showell type polyoxometalate (NH4)6 [Co2Mo10O38H4]·11H2O (Co2Mo10) as a precursor and thiourea in a hydrothermal reaction. The optimized Co–CuS/MoS2 exhibited outstanding hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) activities, with overpotentials of 90 mV and 270 mV at a current density of 10 mA cm−2, respectively, and demonstrated long-term stability in alkaline electrolytes. The superior performance of this catalyst is attributed to the high charge transfer rates between MoS2 and CuS, abundant heterostructure interfaces, and efficient diffusion channels. This study provides a new design strategy for exploring efficient bifunctional electrocatalysts.

Fabrication of In-doped CdSe/Zn3In2S6 type II heterojunction composite for efficient photocatalytic hydrogen evolution

Conversion of water into renewable hydrogen energy using solar energy is one of the ideal methods to address the current environmental pollution and increasing energy demand. Thus developing the photocatalyst with high efficiency, stability, and a low electron-hole recombination rate becomes very important. In this paper, Zn3In2S6 microspheres were synthesized by hydrothermal method, and then In-doped CdSe nanoparticles were loaded on the surface of Zn3In2S6 microspheres to form Cd0.9In0.1Se/Zn3In2S6 type II heterojunction. Under simulated sunlight irradiation, the photocatalytic hydrogen production of Cd0.9In0.1Se/Zn3In2S6 reached 11.41 mmol h−1 g−1, which was 4.61 times and 1.97 times that of Cd0.9In0.1Se and Zn3In2S6, respectively. The experimental results showed that the formation of type II heterojunction could improve the photocatalytic hydrogen production efficiency by shortening the charge transport distance and inhibiting the recombination of electron-hole pairs. This work will provide new ideas and insights for the development of photocatalytic hydrogen production technology.

Ultra-Fast Synthesis of Highly Dispersed Pt Nanoclusters Anchored on Sulfur-Doped Porous Carbon Carriers by Nanosecond Pulsed Laser for Hydrogen Evolution Reaction.

Nanosecond pulsed laser irradiation is employed for synthesis of highly active and stable Pt-based electrocatalysts by anchoring Pt nanoclusters on porous sulfur-doped carbon supports (L-Pt/SC). Strong metal-support interaction (SMSI) between Pt and S induces a local charge rearrangement and modulates the electronic structure of Pt surroundings, thus boosting the reaction kinetics and enhancing stability in long-term hydrogen evolution reaction (HER). The L-Pt/SC catalyst exhibits high activity toward HER, with an overpotential of 23 mV at current densities reaching 10 mA cm-2 and a Tafel slope of 24mV dec-1. The unit mass activity of L-Pt/SC is calculated to be -10.8 A cm-2 mgPt -1 at an applied voltage of -0.3V versus RHE. In situ Raman spectra reveals that L-Pt/SC catalyst exhibits fast hydrogen production efficiency and its electrocatalytic HER process is determined by the Tafel step. Density functional theory calculations suggest the strong bonding energy between SC and Pt induces the formation of smaller nanoclusters of L-Pt/SC during fast pulsed laser preparation, which increases the effective contact area during the HER process thereby increasing the activity per unit mass.

Efficient Water Reforming of Biomass to H2 via Well-Organized Redox-Neutral Cleavage of C-C, O-H and C-H Bonds.

Hydrogen (H2) is a clean and environmentally friendly energy carrier. The depletion of fossil fuels makes renewable H2 production highly desirable. Water reforming of renewable biomass to hydrogen, with a relay of natural photosynthesis to biomass, would be an indirect pathway to realize the ideal but extremely challenging photocatalytic overall water splitting to hydrogen, with favorable thermodynamics. Since the seminal work of water reforming of biomass in 1980, great endeavors have been made. Nevertheless, hitherto, the entire kinetic pathway has been elusive, which seriously limits the reforming processes. Using a designed well-organized redox-neutral cleavage of C-C, O-H and C-H bonds enabled by photoelectrocatalysis, here, we show the efficient water reforming of biomass to hydrogen at room temperature, with a yield up to 93%. The clear insights into the kinetic pathway with oxidation of carbon radicals to carbon cations as the indicated rate-determining step, would cast brightness for efficient and sustainable hydrogen production to accelerate the hydrogen economy.

Vinyl-functionalized covalent organic framework via tuning π-conjugation effectively promotes photocatalytic hydrogen evolution

Covalent organic frameworks (COFs) show great potential in photocatalytic water splitting. However, it is still crucial to explore the effect of π-conjugation of COFs on photocatalytic performance. Here, a series of COFs with different degrees of conjugation (DHTA-BD COF, DHTA-STP COF, DHTA-AZO COF) have been investigated through the synergistic effect of varying the planarity and π electronic structures. The results show that the vinyl-functionalized DHTA-STP COF achieves an excellent photocatalytic hydrogen generation rate of 16.1 mmol g1h−1 under visible light conditions, 4.3 times higher than the DHTA-BD COF, and the hydrogen production of the DHTA-AZO COF is extremely low under the same test conditions. Moreover, the synergistic effect of the smaller dihedral angle and ordered π electronic structures with the introduction of vinyl structure in DHTA-STP COF leads to a higher degree of conjugation, facilitating π delocalization efficiency and promoting the redistribution of charges. Experimental and theoretical calculations have demonstrated that DHTA-STP COF is a promising photoactive semiconductor with the strongest photocurrent, the smallest impedance, the narrowest electronic bandgap, and the strongest separation ability of electron-hole pairs. This finding provides guidance for introducing appropriate conjugated units into COFs to improve the photocatalytic hydrogen production efficiency.

Response characteristics of platinum coated titanium bipolar plates for proton exchange membrane water electrolysis under fluctuating conditions

Voltage fluctuations in energy input not only impact the overall hydrogen production efficiency and stability of Proton Exchange Membrane Water Electrolysis (PEMWE) systems but also pose significant challenges to the long-term service life of individual components. This study focuses on the key component − bipolar plates and investigates the response behavior of platinum-coated titanium bipolar plates under simulated fluctuating voltage conditions. By integrating surface phase analysis and electrochemical testing results, this research elucidates the response characteristics of the bipolar plates to different voltage waveforms and frequencies. And the findings hold substantial significance for the upstream energy control in hydrogen production through water electrolysis.

Enhanced hydrogen evolution performance of twinned Mn0.65Cd0.35S with Zn-doped cadmium selenide under visible light irradiation

The cadmium manganese sulfide, despite being recognized as a highly efficient photocatalytic semiconductor for hydrogen evolution, faces significant challenges in terms of charge recombination when used solely as a catalyst for photocatalytic hydrogen production. The construction of heterojunction photocatalysts is regarded as one of the effective strategies to enhance the efficiency of photocatalytic hydrogen production. In this work, Zn-doped CdSe was adopted to enhance the photocatalytic active sites of the twinned Mn0.65Cd0.35S. As results, the photocatalytic hydrogen evolution of Zn–CdSe-1/T-MCS-40 can reach approximately 47447.15 μmol g−1 after 5 h, representing a 15 times increase compared to Mn0.65Cd0.35S. Besides, the hydrogen evolution rate shows almost no significant attenuation after four consecutive cycles (20 h). The significant achievement can be largely attributed to the successful construction of an S-scheme heterojunction of Zn–CdSe-1/T-MCS-40, which effectively minimized the charge transfer distance and suppressed the recombination of photo-generated electron-hole pairs. Additionally, the incorporation of Zn-doped CdSe significantly expands the response range to visible light, thereby providing a conceptual framework for advancing the design of solar-to-chemical energy conversion and effectively guiding the fabrication of metal sulfide-based photocatalytic heterojunctions.

Hydrogen production from ZnCl2 salt: Application of chlor-alkali method

This experimental study investigates the efficiency of hydrogen production from an aqueous ZnCl2 solution using an electrochemical method within a chlor-alkali reactor. A laboratory-scale reactor with separate anode and cathode compartments was constructed for this purpose. The compartments are separated by a Nafion 212 membrane, which prevents the mixing of the anolyte and catholyte solutions while allowing the passage of positive ions (Zn+). Each compartment is equipped with five carbon rod electrodes. The anode chamber is fed with an aqueous ZnCl2 solution, while the cathode chamber is supplied with pure water. The experiments were conducted with a constant electrolyte transfer rate of 0.3g/s into the reactor, at three different cell voltages (5.0, 7.5, and 10.0V) and two different cell temperatures (20 °C and 45 °C). Due to the small reactor dimensions and the dilution effect caused by adding pure water to the cathode compartment which decreases electrolyte density and adversely affects the current a noticeable reduction in hydrogen gas production was observed. Furthermore, the ZnCl2 electrolyte mass flow rate did not significantly impact the current or the generation of hydrogen and chlorine gases. Consequently, no changes were made to the mass flow rate of pure water or the electrolyte. The presence of active chlorine gas was found to cause the erosion of the carbon rod electrodes in the anode chamber. As a result, the amount of chlorine gas produced in the anode chamber is significantly lower than the hydrogen gas produced in the cathode chamber. At a cell temperature of 20 °C, a mass flow rate of 0.3 g/s, and a cell voltage of 5 V with ZnCl2 aqueous solution, the minimum hydrogen production rate is 0.625 mL/min. In contrast, at a cell temperature of 45 °C, a mass flow rate of 0.3 g/s, and a cell voltage of 10 V, the maximum hydrogen production rate is 4.97 mL/min.