Historically, enormous energy has been used in the process of the electrolysis of water, even sea water, to separate hydrogen. But professors at the University of Houston have discovered a catalyst which can be far less costly than traditionally used electrolysis.
Hydrogen is
a fantastic source for clean energy, but the challenge has always been making enough of it to be efficient and at a practical price.
A newly developed catalyst now reportedly addresses both issues, boasting more efficiency for a lower cost than existing solutions - and it can run for 20 hours straight.
According to the University of Houston scientists who developed the catalyst, it ticks all the boxes in terms of durability and energy storage, as well as cost and efficiency.
"Hydrogen is the cleanest primary energy source we have on Earth,"
says one of the team, Paul C. W. Chu. "Water could be the most abundant source of hydrogen if one could separate the hydrogen from its strong bond with oxygen in the water by using a catalyst."
To split water into hydrogen and oxygen, two reactions are needed - one for each element, the two hydrogen atoms from each other and the oxygen atom from the hydrogen. The main issue has been getting an efficient catalyst for the oxygen part of the equation, which is what these researchers say they've now cracked.
Seawater makes up about 96% of all water on earth, making it a tempting resource to meet the world’s growing need for clean drinking water and carbon-free energy. And scientists already have the technical ability to both desalinate seawater and split it to produce hydrogen, which is in demand as a source of clean energy.
But existing methods require multiple steps performed at high temperatures over a lengthy period of time in order to produce a catalyst with the needed efficiency. That requires substantial amounts of energy and drives up the cost.
An oxygen evolving catalyst takes just minutes to grow at room temperature on commercially available nickel foam. Paired with a previously reported hydrogen evolution reaction catalyst, it can achieve industrially required current density for overall seawater splitting at low voltage. The work is described in a paper published in
Energy & Environmental Science.
Zhifeng Ren, director of the Texas Center for Superconductivity at UH (TcSUH) and corresponding author for the paper, said speedy, low-cost production is critical to commercialization.
“Any discovery, any technology development, no matter how good it is, the end cost is going to play the most important role,” he said. “If the cost is prohibitive, it will not make it to market. In this paper, we found a way to reduce the cost so commercialization will be easier and more acceptable to customers.”
Ren’s research group and others have previously reported a nickel-iron-(oxy)hydroxide compound as a catalyst to split seawater, but producing the material required a lengthy process conducted at temperatures between 300 Celsius and 600 Celsius, or as high as 1,100 degrees Fahrenheit. The high energy cost made it impractical for commercial use, and the high temperatures degraded the structural and mechanical integrity of the nickel foam, making long-term stability a concern, said Ren, who also is M.D. Anderson Professor of physics at UH.
To address both cost and stability, the researchers discovered a process to use nickel-iron-(oxy)hydroxide on nickel foam, doped with a small amount of sulfur to produce an effective catalyst at room temperature within five minutes. Working at room temperature both reduced the cost and improved mechanical stability in separating hydrogen, they said.
“To boost the hydrogen economy, it is imperative to develop cost-effective and facile methodologies to synthesize NiFe (nickel-iron) -based (oxy)hydroxide catalysts for high-performance seawater electrolysis,” they wrote. “In this work, we developed a one-step surface engineering approach to fabricate highly porous self-supported S-doped Ni/Fe (oxy)hydroxide catalysts from commercial Ni foam in 1 to 5 minutes at room temperature.”
In addition to Ren, co-authors include first author Luo Yu and Libo Wu, Brian McElhenny, Shaowei Song, Dan Luo, Fanghao Zhang and Shuo Chen, all with the UH Department of Physics and TcSUH; and Ying Yu from the College of Physical Science and Technology at Central China Normal University.
Ren said one key to the researchers’ approach was the decision to use a chemical reaction to produce the desired material, rather than the massive energy-consuming traditional focus on a physical transformation.
“That led us to the right structure, the right composition for the oxygen evolving catalyst,” he said.
See:
https://www.sciencealert.com/new-wa...ould-unlock-hydrogen-s-green-energy-potential
See:
https://uh.edu/news-events/stories/2021/january-2021/01272021ren-seawater-catalyst.php
Capturing
hydrogen by splitting it from
oxygen in water can be achieved now by using low-cost metals like iron and nickel (Fe-Ni) as catalysts, which speed up this chemical reaction while requiring far less energy to do so. Iron and nickel, which are found in abundance on Earth, would replace precious metals ruthenium, platinum and iridium that up until now are regarded as benchmark catalysts in the 'water-splitting' process.
Hartmann352
Despite large losses of vegetation to land clearing, drought and wildfires, carbon dioxide is absorbed and stored in vegetation and soils at a growing rate.
This is called the “land carbon sink”, a term describing how vegetation and soils around the world absorb more carbon dioxide from photosynthesis than they release. And over the past 50 years, the sink (the difference between uptake and release of carbon dioxide by those plants) has been increasing, absorbing at least a quarter of human emissions in an average year.
The sink is getting larger because of a
rapid increase in plant photosynthesis, and
our new research shows rising carbon dioxide concentrations largely drive this increase.
Humans are producing more carbon dioxide. This carbon dioxide is causing more plant growth, and a higher capacity to suck up carbon dioxide. This process is called the “carbon dioxide fertilisation effect” – a phenomenon when carbon emissions boost photosynthesis and, in turn, plant growth.
What we didn’t know until our study is just how much the carbon dioxide fertilisation effect contributes to the increase in global photosynthesis on land.
Since the beginning of the last century, photosynthesis on a global scale has increased in nearly constant proportion to the rise in atmospheric carbon dioxide. Both are
now around 30% higher than in the 19th century, before industrialisation began to generate significant emissions.
Carbon dioxide fertilisation is responsible for at least 80% of this increase in photosynthesis. Most of the rest is attributed to a longer growing season in the rapidly warming
boreal forest and Arctic.
Higher concentrations of carbon dioxide make plants more productive because photosynthesis relies on using the sun’s energy to synthesise sugar out of carbon dioxide and water. Plants and ecosystems use the sugar both as an energy source and as the basic building block for growth.
When the concentration of carbon dioxide in the air outside a plant leaf goes up, it can be taken up faster, super-charging the rate of photosynthesis.
More carbon dioxide also means water savings for plants. More carbon dioxide available means pores on the surface of plant leaves regulating evaporation (called the stomata) can close slightly. They still absorb the same amount or more of carbon dioxide, but lose less water.
The resulting water savings can benefit vegetation in semi-arid landscapes that dominate much of Australia.
A 2013 study analysed
satellite data measuring changes in the overall greenness of Australia. It showed more leaf area in places where the amount of rain hadn’t changed over time. This suggests water efficiency of plants increases in a carbon dioxide-richer world.
In other
research published recently, we mapped the carbon uptake of forests of different ages around the world. We showed forests regrowing on abandoned agricultural land occupy a larger area, and draw down even more carbon dioxide than old-growth forests, globally. But why?
In a mature forest, the death of old trees balances the amount of new wood grown each year. The old trees lose their wood to the soil and, eventually, to the atmosphere through decomposition.
A regrowing forest, on the other hand, is still accumulating wood, and that means it can act as a considerable sink for carbon until tree mortality and decomposition catch up with the rate of growth.
This age effect is superimposed on the carbon dioxide fertilisation effect, making young forests potentially very strong sinks.
In fact, globally, we found such regrowing forests are responsible for around 60% of the total carbon dioxide removal by forests overall. Their expansion by reforestation should be encouraged.
Forests are important to society for so many reasons – biodiversity, mental health, recreation, water resources. By absorbing emissions they are also part of our available arsenal to combat climate change. It’s vital we protect them and plant additional trees.
Nitrogen is often in short enough supply that it’s the primary controller of how much biomass is produced in an ecosystem. If nitrogen is limited, the benefit of the CO2 increase is limited. You can’t merely view CO2 because the overall real world context really matters.
See:
https://theconversation.com/yes-mor...s-no-excuse-to-downplay-climate-change-130603
See:
https://www.scientificamerican.com/article/ask-the-experts-does-rising-co2-benefit-plants1/
Scientists have observed the CO2 fertilization effect in natural ecosystems, including the past couple decades in outdoor forest plots. Artificially doubling CO2 from pre-industrial levels increased trees’ productivity by around 23 percent. However, the growth effect of increased atmospheric CO2 would be diminished over time due to a nitrogen limitation.
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