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Water splitting for solar energy conversion

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Water splitting for solar energy conversion

In order to enable large-scale hydrogen production using solar energy, particulate photocatalysts are being researched as a simple and cost-effective solution to splitting water into hydrogen and oxygen. It is necessary to develop a photocatalyst that can efficiently use visible light, which accounts for a large part of solar energy, in the water decomposition reaction.

Barium tantalum oxynitride (BaTaO2N) is an oxynitride semiconductor material that absorbs visible light up to 650 nm and has a band structure capable of decomposing water into hydrogen and oxygen. Until very recently, it had not been possible to load BaTaO2N granules with co-catalyst fine particles, which are reaction active sites, with good adhesion and high dispersion.

In this study led by the Research Initiative for Supra-Materials of Shinshu University, the co-catalyst fine particles were found to be highly dispersed on the surface of the single crystal fine particles of BaTaO2N synthesized by the flux method when the impregnation-reduction method and the photodeposition method were sequentially applied.

As a result, the efficiency of the hydrogenation reaction using the BaTaO2N photocatalyst has been improved to nearly 100 times that of the conventional one, and the efficiency of the two-step excitation type (Z scheme type) water decomposition reaction in combination with the oxygen generation photocatalyst has also been improved.

Transient absorption spectroscopy reveals that the Pt-assisted catalyst microparticles supported by the new method are less likely to induce recombination of electrons and holes because they efficiently extract electrons from the BaTaO2N photocatalyst .

By supporting a small amount of Pt co-catalyst by the impregnation-reduction method in advance, the reduction reaction on the photocatalyst is promoted without agglutination of Pt fine particles.
As a result, Pt cocatalyst fine particles are evenly supported by photodeposition on BaTaO2N particles. As a result, it is considered that the extraction of electricity by Pt co-catalyst fine granules proceeded efficiently.

It was also confirmed that the use of BaTaO2N, which is synthesized using an appropriate flux and has a low density of defects, is also important for supporting a highly dispersed Pt co-catalyst.

This study dramatically improved the activity of the BaTaO2N photocatalyst and clarified its mechanism. The results of this research are expected to lead to the development of long-wavelength-responsive photocatalysts that drive the water decomposition reaction with high efficiency.

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Flower or power? Campaigners fear lithium mine could kill rare plant

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Flower or power? Campaigners fear lithium mine could kill rare plant


Flower or power? Campaigners fear lithium mine could kill rare plant

By Romain FONSEGRIVES

Rhyolite Ridge, United States (AFP) May 23, 2024






Delicate pink buds sway in the desert breeze, pregnant with yellow pompoms whose explosion will carpet the dusty corner of Nevada that is the only place on Earth where they exist.

Under their roots lie vast reserves of lithium, vital for the rechargeable electric car batteries that will reduce planet-heating pollution.

But campaigners fear the extraction of the precious metal could destroy the flower’s tiny habitat.

“This mine is going to cause extinction,” says Patrick Donnelly, an environmentalist who works at the Center for Biological Diversity, a non-governmental organization.

“They somehow claim that they’re not harming the (plant). But can you imagine if someone built an open-pit mine 200 feet from your house? Wouldn’t that affect your life profoundly?”

The plant in question is Tiehm’s buckwheat.

There are only around 20,000 known specimens, growing in a few very specific places on a total surface area equivalent to around five soccer fields.

In 2022, the wildflower was classified as endangered by US federal authorities, with mining cited as a major threat to its survival.

The plant and the lithium reserve on which it grows embody one of the key challenges and contradictions of the global climate struggle: how much damage can we inflict on the natural world as we seek to halt or reverse the problems we have already created?

– ‘Coexist’ –

Bernard Rowe, boss of Australian miner Ioneer, which holds the mineral rights to the area, says the lithium produced at Rhyolite Ridge “will be sufficient to provide batteries for about 370,000 vehicles” a year.

“We’ll do that year-on-year for 26 years,” he said.

Those nearly 10 million vehicles will go a long way towards meeting the goal President Joe Biden has set of cutting down the nation’s fleet of gas-guzzlers as a way to slash US production of planet-warming pollutants.

So-called zero-emission cars make up around 7.5 percent of new vehicle sales in the United States today — more than double the percentage just a few years earlier.

In California, the figure is more than 20 percent.

And while expansion in the sector has slowed, the category remains the fastest-growing, according to Kelley Blue Book.

And it’s not only in the United States: Global demand for lithium will increase five to seven times by 2030, according to the International Energy Agency.

The difficulty for US manufacturers is that much of the world’s lithium supply is dominated by strategic rival China, as well as Australia and Chile.

“The United States has very, very little domestic production,” said Rowe.

“So it’s important to develop a domestic supply chain to allow for that energy transition, and Rhyolite Ridge will be an integral part of that.”

Ioneer’s plans show that over the years the mine is in operation — it is projected to start producing lithium in late 2027 — around a fifth of the plant’s habitat will be directly affected.

But the company, which has spent $2.5 million researching the plant, says mining will not affect its survival; it is already growing well in greenhouses and biologists think it can be replanted.

“We’re very confident that the mine and Tiehm’s buckwheat can coexist,” Rowe said.

– ‘Greenwashing’ –

Donnelly counters that Ioneer is “basically greenwashing extinction.”

“They’re saying. ‘We’re going to save this plant,’ when actually they are going to send it to its doom,” he said.

Under the company’s plans, the strip mine will use hundreds of trucks, which Donnelly says will raise clouds of dust that will affect photosynthesis and harm the insects that pollinate the plants.

Ioneer says it has already planned mitigation methods, like dust curtains, and keeping the roads wet.

Still, Donnelly says, why not just move the mine? But Rowe counters that it’s not as simple as just digging somewhere else.

Ioneer has invested $170 million since 2016 to demonstrate the feasibility of this site, which it believes is one of the best around.

“Many of these other deposits haven’t had that amount of work, so they’re not viable alternatives to a project like this,” he said.

The US Department of Energy has offered Ioneer a $700 million loan for the project, if the Bureau of Land Management signs off on an operating permit.

Donnelly insists the issue is not just the future of one obscure wildflower, but rather just one example of large-scale biodiversity loss that is threatening millions of plants and animals.

“If we solve the climate crisis, but we drive everything extinct while we do it, we’re still going to lose our world,” he said.

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Tesla breaks ground on huge Shanghai battery plant

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Tesla breaks ground on huge Shanghai battery plant


Tesla breaks ground on huge Shanghai battery plant

by AFP Staff Writers

Shanghai (AFP) May 23, 2024






Tesla broke ground on a massive battery factory in Shanghai on Thursday, Chinese state media reported, making it the US electric car giant’s second plant in the financial hub.

The project was announced last April after boss Elon Musk presented a vague but ambitious plan to investors to turbocharge growth.

However, the company last month reported a 55 percent drop in quarterly earnings, reflecting a decline in EV sales in an intensively competitive market.

The new Shanghai factory should make 10,000 units per year of Tesla’s Megapack batteries, state news agency Xinhua said.

Tesla says Megapacks are intended to store energy and stabilise supply for power grids, with each unit able to store more than three megawatt-hours of power.

The factory is expected to start mass production in 2025, state media said in May.

“I believe the new plant is a milestone for both Shanghai and Tesla,” the company’s vice president Tao Lin told Xinhua.

“In a more open environment, we can… supply the global market with large-scale energy-storage batteries manufactured in China.”

Musk has extensive business interests in China and is a fairly frequent visitor.

In April, he met Chinese Premier Li Qiang, and received a key security clearance for Tesla’s locally produced EVs.

Musk’s interests in China have long raised eyebrows in Washington — President Joe Biden has said in the past that his links to foreign countries were “worthy” of scrutiny.

The battery plant will be Tesla’s second in the Chinese city after its enormous Shanghai Gigafactory, which broke ground in 2019.

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Improved polymer additive enhances perovskite solar cells

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Improved polymer additive enhances perovskite solar cells


Improved polymer additive enhances perovskite solar cells

by Simon Mansfield

Sydney, Australia (SPX) May 16, 2024






Perovskite solar cells, known for their lightweight and flexible nature, are inexpensive and easy to manufacture. They are seen as a promising technology that can be attached to various surfaces. However, these solar cells currently lack durability and efficiency. New research highlights how adding a polymerized ionic liquid to the metal halide perovskite material can improve their performance, potentially facilitating wider adoption of perovskite solar cells.

“The commonly employed solution processing method for fabricating perovskite layers introduces many defects in both the bulk and surface of the perovskite layer. These intrinsic defects within the perovskite absorption layer pose a significant constraint on the overall performance of the devices. Additive engineering has been demonstrated to be effective as a strategy for defect passivation and performance enhancement in perovskite solar cells,” said Qi Cao, a researcher at Northwestern Polytechnical University in Xi’an, China.



Researchers are enhancing the properties of ionic liquids by creating polymerized versions. In this study, they synthesized a poly ionic liquid called poly4-styrenesulfonyl(trifluoremethylsulfonyl)imidepyridine (PSTSIPPyri).



The addition of PSTSIPPyri to the perovskite solar cell helps prevent halide ion migration, maintains the crystal structure, and improves the solar cell’s stability by fixing organic and halide ions.



“To date, researchers have devoted considerable attention to the meticulous selection of additives that enhance the performance of perovskite solar cells. Among these, ionic liquids have received widespread attention. Ionic bonds in ionic liquids tend to be stronger and more stable, and they offer various tunable properties, including viscosity, polarity, and conductivity,” said Xuanhua Li, a researcher at Northwestern Polytechnical University. “This tunability makes it possible to fine-tune the ionic liquid properties to meet the specific requirements of the perovskite film, thereby optimizing device performance.”



Testing of the PSTSIPPyri additive involved aging perovskite films for 300 hours at 85C and 60% relative humidity. The enhanced perovskite film showed a slower rate of change than the control film. It also retained 84.5% of its efficiency after 1000 hours in a high humidity, high heat environment, compared to 43.6% for the control.



Long-term durability tests showed that with PSTSIPPyri, the perovskite solar cell maintained 87.6% of its power conversion efficiency after 1,500 hours of continuous light, while the control only maintained 61.1%.



“Incorporating PSTSIPPyri as an additive leads to a significant enhancement in the power conversion efficiency of inverted perovskite solar cells from 22.06% to 24.62%. They also demonstrate excellent long-term operational stability,” said Cao. “This strategy illustrates the potential of poly ionic liquids as a promising additive for perovskite solar cells, offering both high performance and stability.”



Other contributors include Xingyuan Chen, Tong Wang, Jiabao Yang, Xingyu Pu, Hui Chen, Bingxiu Xue, and Jianbo Yin at Northwestern Polytechnical University in Xi’an, China; Long Jiang at the CNPC Tubular Goods Research Institute in Xi’an, China.



Research Report:Efficiency enhancement to 24.62% in inverted perovskite solar cells through poly (ionic liquid) bulk modification


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