On-demand Hydrogen Generation Research Articles

Hydrogen Evolution Atomic Cluster Catalysts-Decorated Hierarchical Nanoporous Zinc for on-Demand Hydrogen Generation By Metal Hydrolysis

In recent years, there has been an increasing interest in nanoporous metals due to their wide range of applications, including catalysis, electrocatalysis, energy storage, actuation, and plasmonics. However, considerable attention has been given to precious nanoporous metals such as nanoporous Au, Pd, Pt, Ag, and Cu due to their low chemical reactivity, which makes them relatively easy to synthesize and characterize. Less precious nanoporous metals such as nanoporous Zn, Al, and Mg have been rarely fabricated and characterized because of their relatively high chemical reactivity 1. In this talk, I will present a novel, highly scalable approach to making hierarchical nanoporous zinc (NP-Zn) decorated with atomic clusters of hydrogen evolution catalysts for on-demand hydrogen generation by metal hydrolysis. Our approach involves selective etching in combination with galvanic replacement reactions. The conventional selective etching method requires several days to create a monolithic piece of NP-Zn 2. Our approach creates the same amount of hierarchical NP-Zn in less than 5 minutes, instead of several days. In our work, we used focused ion beam/scanning electron microscopy techniques to reveal the internal nanoscale morphology of the hierarchical NP-Zn, and small-angle X-ray scattering to analyze the pore size distribution. In general, when NP-Zn is used for hydrogen generation by metal hydrolysis, the hydrogen generation yield is low, typically around 20%. This is because zinc is naturally a poor hydrogen evolution material. Our process overcomes this issue by creating NP-Zn with its interface decorated with clusters of hydrogen evolution catalysts, which enables hydrogen generation yield exceeding 90% depending on the catalyst loading. References (1) Fu, J.; Welborn, S. S.; Detsi, E. Dealloyed Air- and Water-Sensitive Nanoporous Metals and Metalloids for Emerging Energy Applications. ACS Appl. Energy Mater. 2022, 5 (6), 6516–6544. https://doi.org/10.1021/acsaem.2c00405.(2) Fu, J.; Deng, Z.; Lee, T.; Corsi, J. S.; Wang, Z.; Zhang, D.; Detsi, E. pH-Controlled Dealloying Route to Hierarchical Bulk Nanoporous Zn Derived from Metastable Alloy for Hydrogen Generation by Hydrolysis of Zn in Neutral Water. ACS Appl. Energy Mater. 2018, 1 (7), 3198–3205. https://doi.org/10.1021/acsaem.8b00419.

A multipass catalytic reactor insert for continuous hydrogen generation from methylcyclohexane

Herein we describe a multipass Catalytic Static Mixer (CSM) for implementation in on-demand hydrogen generation. The insert is a 3D printed metal scaffold with a catalyst coating containing a multitude of channels and a hollow core for a heater rod. This next generation of CSMs offers higher throughput and increased residence times for applications involving liquid-gas or gas only flow. We have implemented this CSM as an insert in a continuous flow tubular reactor for the dehydrogenation of Liquid Organic Hydrogen Carriers (LOHCs). The catalyst coating is comprised of 5 wt.% Pt/Al2O3 and is used for the dehydrogenation of methylcyclohexane (MCH) to generate hydrogen gas as the model system. This experimental study investigates the thermal profiles of the reactor and validates the potential of the CSM technology in hydrogen generation from LOHCs.

Two-dimensional molybdenum boride coordinating with ruthenium nanoparticles to boost hydrogen generation from hydrolytic dehydrogenation of ammonia borane

The coordination between carrier and active metal is critical to the catalytic efficiency of ammonia borane (AB) hydrolysis reaction. In the present study, we report a new type of catalytic support based on molybdenum boride (MBene) MoAl1-xB and demonstrate that the effective combination of MoAl1-xB with Ru nanoparticles can realize the significantly enhanced performance for hydrogen generation. Owing to the efficient activation and dissociation of reactants, the optimal Ru/MoAl1-xB catalyst achieves the large turnover frequency of 494 molH2 molRu-1 min−1, high hydrogen generation rate of 119817 mL min−1 gRu-1 and favorable apparent activation energy of 39.2 kJ mol−1 for the catalytic hydrolysis of AB under alkaline-free condition. The isotopic test suggests the cleavage of OH bond in H2O is the rate-determining step for hydrolysis reaction, while the fracture of B–H bond in AB is also well revealed by attenuated total reflectance (ATR)-Fourier transform infrared (FTIR) spectroscopy. Significantly, the flexible on-demand hydrogen generation is achieved by using chemical switches for on–off AB hydrolysis. This study provides a new support platform based on two-dimensional MBene to exploit efficient catalysts to boost AB dehydrogenation.

Highly efficient immobilized PN3P-pincer iridium catalyst for dehydrogenation of neat formic acid

Formic acid (FA) has been well recognized as one of the most promising hydrogen carriers. The dehydrogenation of the FA could offer an efficient process to on-demand hydrogen generation with a suitable catalyst. Homogeneous catalysts have demonstrated superior activity and selectivity compared to traditional heterogeneous catalysis. However, the latter is preferred for large-scale applications. By incorporating the homogeneous organometallic complex onto an appropriate support, the unique features of both types of catalysts can be combined and utilized effectively. Herein, we synthesized an immobilized PN3P-Ir pincer catalyst (2) supported onto KCC-1, a 3D fibrous silica nanosphere that exhibits a high surface area and contains a tetracoordinate aluminum site. To reduce the use of volatile additives, the choice of cesium formate (CsO2CH) was found to be crucial as at 80–90 °C, CsO2CH could act as a reaction medium and serve as basic additive. Remarkable reactivities under neat conditions were achieved with a TOF of 13,290 h-1 and a TON of up to 540,000. The comparative study indicates a significant improvement of 2 from its homogenous counterpart, PN3P-IrH3 (1).

Strategy for Hydrogen Generation from a Photovoltaic System Using a Boost Converter

This research presents two schemes for hydrogen generation by alkaline water electrolysis using a photovoltaic system and a boost converter as a power source. The first scheme aims to extract the maximum power from the photovoltaic system using the P&O algorithm and use this energy to generate hydrogen. Thus, obtaining the maximum efficiency of the photovoltaic-electrolytic cell system. The second scheme aims to generate hydrogen on demand, eliminating the need for storage and reducing the associated costs and risks. Nevertheless, this approach does not fully maximize the power available in the PV system, resulting in lower overall efficiency. Finally, it concludes with the proposal of an approach that combines on-demand hydrogen generation and maximum energy extraction from solar panels. Any unused energy from the electrolytic reactor is stored in a battery bank through a bidirectional converter. However, the simulation and implementation of this third scheme are proposed as future work.

When Pt nanoparticles meet oxygen-deficient Co3O4: Enabling superior performance towards on-demand hydrogen generation from hydrolytic dehydrogenation of dimethylamine borane

The regulation of the metal-support interaction in heterogeneous catalysts can promote the activation of reactants, which is beneficial for the hydrolytic dehydrogenation reaction. Herein, the hydrolytic dehydrogenation of dimethylamine borane (DMAB) is systematically studied on the oxygen vacancy (Ov) enriched Pt-Co3O4 heterogeneous catalyst with the metal-support interaction. It is found that the metallic Pt site facilitates the adsorption of DMAB molecules and the Ov on Co3O4 support as an electron-rich center cooperates with the adjacent Pt site to dissociate water molecules. The in situ Raman and attenuated total reflectance (ATR)-Fourier transform infrared (FTIR) spectroscopy reveal the effective activation and cleavage of the O-H in water and the B-H in DMAB over the Pt-Co3O4 catalyst. The optimal Pt-Co3O4 catalyst exhibits the extraordinary activity for the catalytic hydrolysis of DMAB at 303 K, delivering a high specific hydrogen generation rate (64063 mL min−1 gpt−1) and a competitive turnover frequency (TOF, 23880 molH2 molPt−1 h−1). This performance outperforms most of the reported heterogeneous catalysts for DMAB dehydrogenation. More importantly, the Pt-Co3O4 catalyst achieves the desirable on-demand hydrogen production by using special chemical switches. This finding provides the fundamental understanding of metal-oxide systems with the collaborative interfacial catalysis for boosting DMAB dehydrogenation.

Nitridation-activated Al flakes for hydrogen generation on-demand

The on-demand generation of hydrogen from aluminium particles can be a promising approach to alleviate air pollution from town gas production facilities during peak operation periods. Overcoming the challenges of disrupting the protective alumina film on aluminium particles without using highly corrosive alkaline solutions, energy-intensive processes, or expensive metal additives is crucial. This study reports the hydrolysis of aluminium flakes with gamma-alumina (γAl2O3) and aluminium nitride (AlN) nano inclusions in distilled water. We optimised the growth of these active inclusions via calcination of aluminium flakes in a semi-permeable steel chamber at temperatures ranging from 843 to 903 K. The optimal activation process triggers hydrogen release by hydrolysing AlN within the activated flakes at moderate temperatures (313−353 K). Additionally, we study the synthesis of mesoporous γAl2O3 particles from hydrolysis by-products and explore the potential for harnessing waste heat and ammonium solution in town gas production.

Combustion, performance and emission characteristics of CI engine fueled with diesel and hydrogen based reactor

There is a significant role of using hydrogen in engines than pure disesel, bio diesels. A combination of hydrogen at different flow rates and diesel can be used. Hydrogen tanks with storage capacity is used in vehicle which is very dangerous, so here we include a hydrogen reactor in which chemicals are mixed to produce hydrogen and can be sent to the engine along with diesel. In this work, an on-demand hydrogen generation setup was used to generate hydrogen for the purpose of burning it in the engine along with diesel under dual fuel mode. A solid-state hydrogen generation mechanism was employed in a purpose-built reactor using Sodium Borohydride (NaBH4) and Aluminium Sulphate (Al2(SO4)3) mixed in water. The experimentation was done on 4 S VCR diesel engine with single cylinder which was modified into duel fuel mode. The studies were carried with pure diesel and hydrogen at 15lit per min at 16, 17 and 18 compression ratioby holding speed to be 1500 rpm with varied loads from 0 to 12 kg with an interval of 3 kg. The cylinder pressure got increased, performance parameters like brake thermal efficiency got enhanced due to the usage of hydrogen than pure diesel. The emission parameter such as nitrogen oxide increased when hydrogen was injected.

The effect of cracks and alloy phase conditions on the hydrolysis characteristics of Al-10Bi alloy powder (composites)

The Al-water reaction has attracted many attentions as it's a convenient method for on-demand hydrogen generation. Although a variety of additives have been demonstrated to promote the activity of Al, the most likely mechanism is simply the inference made from surface conditions and reaction characteristics. In this study, the activation of two kinds of active Al-10Bi alloys powders was prepared by both melting alloy and mechanical alloy methods. The activity of the as obtained powders was analyzed through various methods including XRD, SEM. 3D characterization of active Al powders was conducted using synchrotron X-ray tomography to reveal the inner structure of ball milled active Al alloy powders. Results show that ball milling could effectively introduce a large number of cracks both on the surface and the inner of powders. The number of cracks increased further after adding salt during ball milling. The relation between the inner structure of the Al alloys and their hydrolysis reaction products was also discussed. The specific surface area, the number and distribution of cracks alloy phase are all important factors that influence the hydrolysis reaction of the active alloy powder.

Hydrogen production from formic acid in fluidized bed made out of Ni-cenosphere catalyst

This research presents a method of hydrogen production from formic acid with the use of fluidized bed technology. The core-shell catalyst was developed by applying the Ni layer on cenospheres via a technique of gaseous deposition. The efficiency of the decomposition of formic acid was tested continuously in the range of 200–500 °C. An analytical method, based on infrared spectroscopy, allowing the continuous monitoring of the concentration of products in the gas phase has been developed. A 67% yield of hydrogen was achieved at 233 °C. The proposed solution in a fluidized bed has been compared with other methods of obtaining hydrogen from formic acid. The most important advantages of the proposed solutions are on-demand hydrogen generation; the use of an energy carrier that can be obtained from biomass or CO2; simplicity of the process including easy control of the process temperature; repeatability; ease of scaling the fluidized process; the possibility of continuous monitoring of the products of the process; high efficiency of hydrogen generation per unit volume of the reactor.

Novel synthetic co-culture of Acetobacterium woodii and Clostridium drakei using CO2 and in situ generated H2 for the production of caproic acid via lactic acid.

Acetobacterium woodii is known to produce mainly acetate from CO2 and H2, but the production of higher value chemicals is desired for the bioeconomy. Using chain-elongating bacteria, synthetic co-cultures have the potential to produce longer-chained products such as caproic acid. In this study, we present first results for a successful autotrophic co-cultivation of A.woodii mutants and a Clostridium drakei wild-type strain in a stirred-tank bioreactor for the production of caproic acid from CO2 and H2 via the intermediate lactic acid. For autotrophic lactate production, a recombinant A. woodii strain with a deleted Lct-dehydrogenase complex, which is encoded by the lctBCD genes, and an inserted D-lactate dehydrogenase (LdhD) originating from Leuconostoc mesenteroides, was used. Hydrogen for the process was supplied using an All-in-One electrode for in situ water electrolysis. Lactate concentrations as high as 0.5g L-1 were achieved with the AiO-electrode, whereas 8.1gL-1 lactate were produced with direct H2 sparging in a stirred-tank bioreactor. Hydrogen limitation was identified in the AiO process. However, with cathode surface area enlargement or numbering-up of the electrode and on-demand hydrogen generation, this process has great potential for a true carbon-negative production of value chemicals from CO2.

The Hydrolysis of Ball-Milled Aluminum–Bismuth–Nickel Composites for On-Demand Hydrogen Generation

The hydrolysis of aluminum (Al) is a promising method for on-demand hydrogen generation for low-power proton exchange membrane fuel cell (PEMFC) applications. In this study, Al composites were mechanochemically activated using bismuth (Bi) and nickel (Ni) as activation compounds. The main objective was to determine the effects of Bi and Ni on Al particles during mechanochemical processing, and the hydrolysis activity of the Al-Bi-Ni composites. Successfully formulated ternary Al-Bi-Ni composites were hydrolyzed with de-ionized water under standard ambient conditions to determine the reactivity of the composite (extent of hydrogen production). Scanning electron microscopy (SEM) showed that Bi and Ni were distributed relatively uniformly throughout the Al particles, resulting in numerous micro-galvanic interactions between the anodic Al and cathodic Bi/Ni during hydrolysis reaction. The addition of >1 wt% Ni resulted in incomplete activation of Al, and such composites were non-reactive. All successfully prepared composites had near-complete hydrogen yields. X-ray diffraction (XRD) showed that no mineralogical interaction occurred between Al, Bi, and/or Ni. The main phases detected were Al, Bi, and minute traces of Ni (ascribed to low Ni content). In addition, the effect of the mass ratio (mass Al:mass water) and water quality were also determined.

Study on the liquid phase-derived activation mechanism in Al-rich alloy hydrolysis reaction for hydrogen production

Bulk Al-Ga-In-Sn alloys are potential on-demand hydrogen generation materials, and Ga, In, and Sn with fascinating liquid characteristics manifest extraordinary activation capabilities in an Al–H2O reaction for hydrogen production. In the present work, the hydrogen production performances of Al-rich alloys were explored and the corresponding activation mechanism was investigated. The actual composition of the grain boundary (GB) phase in each alloy was determined by the Ga-In-Sn ternary phase diagram. A significant morphological transformation in the grain boundary particles (GBPs) was observed. Based on the surface tension of GBPs, the “Marangoni effect” was used to explain the hydrogen release rates of different alloys during hydrolysis. In addition, a liquid phase-derived activation mechanism during Al hydrolysis was proposed. The as-cast Al-Ga-In-Sn alloys were also used as energy carriers, and the power-consuming load was successfully supplied through the on-demand hydrogen supply mode, verifying the feasibility of liquid phase-activated Al-rich alloys in hydrogen energy applications.

Aluminum Nanoparticles from a Ga–Al Composite for Water Splitting and Hydrogen Generation

We report the use of a gallium (Ga)-rich aluminum (Al) composite to enhance the formation of Al nanoparticles and to facilitate its ability to split water to generate hydrogen at ambient conditions. The synthesis of this Ga–Al composite occurs without the need of an inert atmosphere or mechanical aid. Commercial Al can be used, including postconsumer aluminum foil that is usually discarded. Characterization of the Ga–Al composite with scanning electron microscopy, energy-dispersive X-ray spectroscopy, and powder X-ray diffraction illustrates that the Ga acts to dissolve the aluminum oxide coating of the Al nanoparticles. The pristine nanoparticles are then available for continuous water splitting and on-demand hydrogen generation through the Grotthuss mechanism. The water-splitting reaction does not require an applied potential and functions at ambient conditions and neutral pH to rapidly generate 130 mL (5.4 mmol) of hydrogen per gram of alloy. Any available source of water can be used including wastewater, commercial beverages, or even ocean water, with no generation of chlorine gas, as confirmed by gas chromatography–mass spectrometry. In addition, Ga remains intact, allowing it to be collected and reused indefinitely. The Ga–Al alloy is stable under cyclohexane for at least 3 months so it can be preprepared for a later use. As an initial example of the application of evolved hydrogen, we show a hydrogenation reaction.

On-Demand Hydrogen Generation by the Hydrolysis of Ball-Milled Aluminum-Bismuth-Zinc Composites.

In this investigation, ternary Al-Bi-Zn composites were prepared through mechanochemical activation to determine the combined effects of low-cost Bi and Zn on the morphology change and reactivity of the Al composite during the hydrolysis reaction. Specifically, Zn was considered as a means to slow the hydrogen generation rate while preserving a high hydrogen yield. A steady hydrogen generation rate is preferred when coupled with a proton exchange membrane fuel cell (PEMFC). Scanning electron microscopy (SEM) analysis indicated that Bi and Zn were distributed relatively uniformly in Al particles. By doing so, galvanic coupling between anodic Al and the cathodic Bi/Zn sustains the hydrolysis reaction until the entire Al particle is consumed. X-ray diffraction analysis (XRD) showed no intermetallic phases between Al, Bi, and/or Zn formed. A composite containing 7.5 wt% Bi and 2.5 wt% Zn had a hydrogen yield of 99.5%, which was completed after approximately 2300 s. It was further found that the water quality used during hydrolysis could further slow the hydrogen generation rate.

Electrochemically controlled ON/OFF switching of NaBH4 hydrolysis based on NiMoN@NC for on-demand hydrogen production.

A facile and novel electrochemically controlled ON/OFF switching of NaBH4 hydrolysis is proposed for on-demand hydrogen production. A low potential can activate the catalyst to the ON state by promoting the adsorption and hydrolysis of BH4-, while a high potential can deactivate the catalyst to the OFF state by inhibiting the chemical hydrolysis.

On-demand hydrogen generation by the hydrolysis of ball-milled aluminum composites: A process overview

The hydrolysis of aluminum (Al) is a relatively simple method for on-demand hydrogen generation for niche (low-power, <1 kW) proton exchange membrane fuel cell applications. The hydrolysis of Al in neutral pH water and under standard ambient conditions is prevented by the presence of a thin surficial oxide layer. A promising method to enable Al's spontaneous hydrolysis is by its mechanochemical activation (ball milling) with certain metals (e.g., Bi, Sn, In, Ga). This overview presents several aspects relating to the changes occurring in Al particles during ball milling, e.g., the structural and morphological behavior of Al during ball milling procedures (with and without the presence of activation metals), and the distribution and homogenization of Al and various activation metals. The formation of galvanic cells between anodic Al and cathodic activation metals (relative to Al) is discussed. A summary of the existing Al composites for on-demand hydrogen generation is presented. The paper concludes with a discussion of activation metal recovery, and the effects thereof on the economic feasibility of Al composites for hydrogen generation.

Eco-Friendly Synthesis of Nanoporous Magnesium By Air-Free Electrolytic Dealloying of Magnesium-Lithium Alloy with Recovery of Sacrificial Lithium

In recent years, air- and water-sensitive nanostructured materials with minimal surface oxide coverage have received increased attention for their potential role in various applications, such as catalysts for combustion fuels, active ingredients in solid-propellant rockets, and reactants for onboard and on-demand hydrogen generation to feed fuel cells. However, the fabrication of this class of materials has been hindered by their inherently high chemical reactivity. Magnesium, with its standard reduction potential of -2.37 V vs. SHE, is highly water-reactive in its nanostructured form, thus the synthesis of nanostructured magnesium with minimal surface oxide coverage poses a challenge. In this talk, I will introduce a novel eco-friendly air-free selective electrolytic leaching route to fabricate three-dimensional (3D) bicontinuous nanoporous magnesium (NP-Mg) with minimal surface oxide coverage. The starting material consists of a Mg-Li parent alloy, with lithium as the sacrificial component. During selective electrolytic leaching in an anhydrous lithium-conducting organic electrolyte solvent, the sacrificial lithium is stripped from the Mg-Li parent alloy used as the working electrode and plated on a pure lithium foil used as the counter electrode. This process enables sacrificial element recovery, making it eco-friendly. The dealloyed NP-Mg exhibits a characteristic ligament and pore size in the range of 20-30 nm, and its morphology was thoroughly investigated using electron microscopy, inductively coupled plasma (ICP) spectroscopy, small-angle X-ray scattering (SAXS), and X-ray diffraction, as will be shown during my talk. NP-Mg with such ultra-small feature size could be attractive for several applications including hydrogen storage in the form of magnesium hydride, and on-demand hydrogen generation by hydrolysis with pure water.

Boosting the on-demand hydrogen generation from aqueous ammonia borane by the visible-light-driven synergistic electron effect in antenna-reactor-type catalysts with plasmonic copper spheres and noble-metal-free nanoparticles

To tailor the electronic behavior of catalytically active species in heterogeneous catalysts is beneficial for regulating their catalytic performance in various reaction including hydrogen generation. Herein, we rationally synthesize a series of antenna-reactor-type catalysts with the combination of plasmonic Cu spheres (55, 130, 190, 270 and 440 nm) with catalytically active Co or Ni nanoparticles (NPs), which are used for hydrogen generation from aqueous ammonia borane (NH3BH3) at 298 K. All the catalysts show the higher activities under visible light irradiation than in the dark and the optimal Co-based catalyst has the highest room-temperature photocatalytic activity with the total turnover frequency (TOF) value of 164.8 min−1, which outperforms the values of all the reported non-noble metal catalysts. The capture of photogenerated electrons, the monochromatic light-dependent activity and hydrogen generation of different catalysts verify that there exists the visible-light-driven synergistic electron effect bewteen plasmonic Cu spheres with energetic electrons and Co NPs with excited electrons generated by interband transitions. This leads to the electron density enrichment of Co NPs and the resultantly enhanced hydrogen generation activity under visible light irradiation.

On-demand production of hydrogen by reacting porous silicon nanowires with water

On-demand hydrogen generation is desired for fuel cells, energy storage, and clean energy applications. Silicon nanowires (SiNWs) and nanoparticles (SiNPs) have been reported to generate hydrogen by reacting with water, but these processes usually require external assistance, such as light, electricity or catalysts. Herein, we demonstrate that a porous SiNWs array, which is fabricated via the metal-assisted anodic etching (MAAE) method, reacts with water under ambient and dark conditions without any energy inputs. The reaction between the SiNWs and water generates hydrogen at a rate that is about ten times faster than the reported rates of other Si nanostructures. Two possible sources of enhancement are discussed: SiNWs maintain their high specific surface area as they don’t agglomerate, and the intrinsic strain of the nanowires promotes the reactivity. Moreover, the porous SiNWs array is portable, reusable, and environmentally friendly, yielding a promising route to produce hydrogen in a distributed manner.