Tag: green hydrogen

Groundbreaking advancements in net-zero technology

Groundbreaking advancements in net-zero technology

A transnational collaborative research team, comprising Jeng-Lung Chen, Assistant Scientist, Yu-Chun Chuang, Associate Scientist, and Chung-Kai Chang, Research Assistant from the National Synchrotron Radiation Research Center (NSRRC) under the purview of the National Science and Technology Council, in partnership with Dr. Lu-Ning Chen, Professor Gabor A. Somorjai, and Dr. Ji Su from the Lawrence Berkeley National Laboratory in California, USA, has dedicated three years to pioneering global advancements in the field of green hydrogen production. Their groundbreaking work centers around the development of a methane pyrolysis catalyst, known as the “nickel-molybdenum-bismuth liquid alloy (NiMo-Bi),” which exhibits high hydrogen production efficiency, excellent stability, and low energy consumption. This study explored the electrostatic charge distribution on the active nickel sites in the molten state, demonstrating the NiMo-Bi liquid alloy’s capability to effectively mitigate the cage effect caused by bismuth. This mitigation facilitates the effective flow of methane to active nickel sites, resulting in efficient hydrogen generation. This outstanding discovery was published in the respected international journal Science on August 25, 2023, emerging as a pivotal driving force for advancing the transition to a net-zero future.  

The U.S. research team initially integrated molybdenum into the nickel-bismuth catalyst, resulting in the creation of an innovative catalyst known as NiMo-Bi liquid alloy. Meanwhile, NSRRC scientists engineered an experimental setup tailored for in-situ high-temperature gas-phase reactions. Harnessing the capabilities of the “Quick X-ray Absorption Spectroscopy Beamline” and the “High Resolution Powder X-ray Diffraction Beamline” at the Taiwan Photon Source (TPS), the team validated the catalyst’s efficacy by significantly lowering methane pyrolysis temperatures to values as low as 450 °C. They also showed that at an elevated temperature of 800 °C, the selectivity of converting methane into hydrogen reached 100%, maintaining this optimal level for a stable period of 120 hours. This achievement marks a nearly 37-fold improvement in hydrogen production efficiency compared to previous methods. Concurrently, the optimal pyrolysis temperature was significantly reduced from 1065 degrees Celsius to 800 degrees Celsius, resulting in a significant reduction in the energy requirements of the conversion process.

Read more on the NSRRC website

Image: Quick X-ray Absorption Spectroscopy Beamline

BESSY II: Surface analysis of catalyst particles in aqueous solutions

BESSY II: Surface analysis of catalyst particles in aqueous solutions

In a special issue on the liquid jet method, a team reports on reactions of water molecules on the surfaces of metal oxide particles. The results are relevant for the development of efficient photoelectrodes for the production of green hydrogen.

Green hydrogen can be produced directly in a photoelectrochemical cell, splitting water with solar energy. However, this requires the development of super-efficient photoelectrodes that need to combine many talents at the same time: They must be excellent at converting sunlight into electricity, remain stable in acidic or basic water, act as catalysts to promote the splitting of water into hydrogen and oxygen, and be cheap, abundant and non-toxic. The large material class of metal oxides comes into question. However, it is difficult to find out what really happens at the interfaces between the solid metal oxide electrodes and the aqueous electrolyte. This is because standard X-ray analysis does not work to investigate processes on samples in liquid environments. One of the few suitable methods are experiments with a liquid jet: an extremely fine jet of liquid in which nanoparticles of metal oxide are suspended. This jet shoots through the X-ray light of BESSY II, and the interference of the evaporated molecules with the measurement data is negligible (more in the foreword to the special issue).

Dr. Robert Seidel is an expert on this liquid jet method, which is the subject of a special issue of Accounts of Chemical Research. He was invited to be the guest-editor of the issue and to report also on new experiments at BESSY II that he conducted with Dr. Hebatallah Ali and Dr. Bernd Winter from the Fritz Haber Institute.

They investigated two important model systems for photoelectrodes: Nanoparticles of iron oxide (hematite, α-Fe2O3, and anatase (titanium oxide or TiO2) in aqueous electrolytes with different pH values. Hematite and anatase in suspension are photocatalytic model systems. They are ideal for studying the solid/electrolyte interface at the molecular level and for exploring the chemical reactions at electrode-electrolyte interfaces.

“We used resonant photoelectron spectroscopy (PES) to identify the characteristic fingerprints of different reactions. This allowed us to reconstruct which reaction products are formed under different conditions, particularly as a function of pH.” The key question: How do the water molecules react with or on the nanoparticle surfaces?

In fact, how acidic or how basic an electrolyte is makes a big difference, Seidel noted. “At low pH, the water molecules on the surface of hematite tend to split. This is not the case with anatase, where water molecules are adsorbed on the surface of the TiO2 nanoparticles,” says Seidel. A basic pH value is required for water molecules to break down on the anatase nanoparticles. “Such insights into surface interactions with water molecules are only possible with this liquid-jet method,” says Seidel.

The spectra also revealed ultra-fast electron transitions between the metal oxide and the (split) water molecules on the surface. The results provide insights into the first steps of water dissociation and help to clarify the mechanisms of light-induced water splitting on metal oxide surfaces.

Read more on this story here

Image: The microjet is a fast-flowing stream of liquid so narrow that it produces only an extremely dilute vapour cloud. Photons and particles can reach and leave the surface of the jet without colliding with the vapour molecules.

Electrocatalysis – Iron and Cobalt Oxyhydroxides examined

Electrocatalysis – Iron and Cobalt Oxyhydroxides examined

A team led by Dr. Prashanth W. Menezes (HZB/TU-Berlin) has now gained insights into the chemistry of one of the most active anode catalysts for green hydrogen production. They examined a series of Cobalt-Iron Oxyhydroxides at BESSY II and were able to determine the oxidation states of the active elements in different configurations as well as to unveil the geometrical structure of the active sites. Their results might contribute to the knowledge based design of new highly efficient and low cost catalytical active materials.

Very soon, we need to become fossil free, not only in the energy sector, but as well in industry. Hydrocarbons or other raw chemicals can be produced in principle using renewable energy and abundant molecules such as water and carbon dioxide with the help of electrocatalytically active materials. But at the moment, those catalyst materials either consist of expensive and rare materials or lack efficiency.

Key reaction in water splitting

A team led by Dr. Prashanth W. Menezes (HZB/TU-Berlin) has now gained insights into the chemistry of one of the most active catalysts for the anodic oxygen evolution reaction (OER), which is a key reaction to supply electrons for the hydrogen evolution reaction (HER) in water splitting. The hydrogen can then be processed into further chemical compounds, e.g., hydrocarbons. Additionally, in the direct electrocatalytic carbon dioxide reduction to alcohols or hydrocarbons, the OER also plays a central role.

Read more on the HZB website

Image: LiFex-1Cox Borophosphates have been used as inexpensive anodes for the production of green hydrogen. Their dynamic restructuring during OER as well as their catalytically active structure, have been elucidated via  X-ray absorption spectroscopy.

Credit: © P. Menezes / HZB /TU Berlin

Green hydrogen: Nanostructured nickel silicide shines as a catalyst

Green hydrogen: Nanostructured nickel silicide shines as a catalyst

Electrical energy from wind or sun can be stored as chemical energy in hydrogen, an excellent fuel and energy carrier. The prerequisite for this, however, is efficient electrolysis of water with inexpensive catalysts. For the oxygen evolution reaction at the anode, nanostructured nickel silicide now promises a significant increase in efficiency. This was demonstrated by a group from the HZB, Technical University of Berlin and the Freie Universität Berlin as part of the CatLab research platform with measurements among others at BESSY II.

Electrolysis might be a familiar concept from chemistry lessons in school: Two electrodes are immersed in water and put under voltage. This voltage causes water molecules to break down into their components, and gas bubbles rise at the electrodes: Oxygen gas forms at the anode, while hydrogen bubbles form at the cathode. Electrolysis could produce hydrogen in a CO2-neutral way – as long as the required electricity is generated by fossil free energy forms such as sun or wind.

The only problem is that these reactions are not very efficient and extremely slow. To speed up the reactions, catalysts are used, based on precious and rare metals such as platinum, ruthenium or iridium. For large-scale use, however, such catalysts must consist of widely available and very cheap elements.

Read more on the HZB website

Image: Crystalline nickel silicide (left) is chemically transformed into nanostructured material with excellent catalytic properties for the electrolytic splitting of water and the production of valuable nitrile compounds. 

Credit: © P. Menezes /HZB/TU Berlin

Green hydrogen: Why do certain catalysts improve in operation?

Green hydrogen: Why do certain catalysts improve in operation?

Crystalline cobalt arsenide is a catalyst that generates oxygen during electrolytic water splitting in the production of hydrogen. The material is considered to be a model system for an important group of catalysts whose performance increases under certain conditions in the course of electrolysis. Now a HZB-team headed by Marcel Risch has observed at BESSY II how two simultaneous mechanisms are responsible for this. The catalytic activity of the individual catalysis centres decreases in the course of electrolysis, but at the same time the morphology of the catalyst layer also changes. Under favourable conditions, considerably more catalysis centres come into contact with the electrolyte as a result, so that the overall performance of the catalyst increases.

As a rule, most catalyst materials deteriorate during repeated catalytic cycles – they age. But there are also compounds that increase their performance over the course of catalysis. One example is the mineral erythrite, a mineral compound comprising cobalt and arsenic oxides with a molecular formula of (Co3(AsO4)2∙8H2O). The mineral stands out because of its purple colour. Erythrite lends itself to accelerating oxygen generation at the anode during electrolytic splitting of water into hydrogen and oxygen.

Read more in the HZB website

Image: Schematic of the electrochemical restructuring of erythrite. The fine needle-like structure melts during the conversion from a crystalline material to an amorphous one, which is porous like a Swiss cheese.

Credit: © HZB

Turning straw into gold?

Turning straw into gold?

A more profitable and eco-friendly method for turning biomass into biochemicals and green hydrogen

Many have dreamed of being able to turn straw into gold like the fabled Rumpelstiltskin. While this may not be possible in the literal sense, scientists are using sunlight to turn straw into something more valuable.

With the aid of technology from the Canadian Light Source (CLS) at the University of Saskatchewan, Canadian researchers have made important advances to use the power of the sun to convert biomass like wheat straw into hydrogen fuel and value-added biochemicals. This method is more efficient, eco-friendly and lucrative.

Producing energy from biomass, or plant material, has been studied for more than four decades, said Dr. Jinguang Hu, assistant professor at the University of Calgary (UCalgary). The two most common processes are thermo-chemical and biological, but these are still carbon intensive and are not economically feasible.

Read more on the CLS website

Image: The UCalgary team is observing a photo-reactor that is being used for a photoreforming reaction with wheat straw. Left to right: Prof. Md Golam Kibria, Dr. Adnan Khan (Research Associate), Dr. Heng Zhao (Post doctoral fellow), Prof. Jinguang Hu.

Credit: Prof. Hu and Kibria group.