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Researchers Convert Biomass To Hydrogen Using Sunlight (rdmag.com)
New submitter omaha393 writes: Cambridge chemists have developed a new catalytic approach capable of converting biomass into hydrogen gas using only sunlight as an energy source. The method converts lignocellulose, one of Earth's most abundant biomaterials, into hydrogen gas and organic byproducts when in a basic water and in the presence of the cadmium sulfide/oxide nanoparticle catalysts. The new method, published in Nature Energy, offers a relatively cheap fuel alternative that researchers are looking to scale up to meet consumer demands at the industrial level. Per R&D Magazine: "'With this in place we can simply add organic matter to the system and then, provided it's a sunny day, produce hydrogen fuel,' says joint lead author David Wakerley. 'Future development can be envisioned at any scale.'" In addition to lignocellulose, the team was also able to produce hydrogen gas using unprocessed material including wood, paper and leaves. Further reading: New Atlas; ScienceDaily
"The system operates under visible light, is stable beyond six days and is even able to reform unprocessed lignocellulose, such as wood and paper, under solar irradiation at room temperature, presenting an inexpensive route to drive aqueous proton reduction to H2 through waste biomass oxidation."
It uses Cadmium compounds in water. With the use of such an environmental toxin, I sincerely hope it's stable for a lot longer than six days.
H2 is one of the worst fuels out there as it will burn in almost any ratio with air, makes leaks very dangerous. It will chew through almost any material you use to contain it so leaks, and the higher the pressure the more it leaks. It has a lowish calorific content, so lots needed to get some energy out of it, but on the good side it can burn very hot so less is wasted.
Hydrogen is not only applicable to hydrogen cars (where you're correct, it doesn't make for a very good fuel choice). It's an incredibly important chemical in industry. As one example among countless, it's one of the two feedstocks (the other being nitrogen) in the Haber process for producing ammonia, which forms the root of all industrial production of nitrated products on Earth (particularly fertilizers). Right now Haber process hydrogen almost exclusively comes from natural gas reforming (CH4 + H2O -> 1 CO + 3 H2; CO + H2O -> CO2 + H2).
Stale pastry is hollow succor to one who is bereft of ostrich.
Well..... it depends on the process ;) Some catalysts are highly stable and last for years without renewal (or even indefinitely), while on the other end of the spectrum some disappear quickly and end up in the product by design (plastics are particularly bad about this, to the point that it blurs the line between catalyst and initiator).
That said, industry constantly uses toxic catalysts in huge quantities. Acting like this is some sort of new horrible development is just silly. Where toxicity might be a concern, the rate of entrainment into the product is measured, and if it's too high for safety, either a new catalyst has to be found, the previous catalyst has to be better stabilized / retained, or you have to add a post-processing step to recover the catalyst from the product.
Stale pastry is hollow succor to one who is bereft of ostrich.
Rather than spending your time reading Wikipedia, I suggest you spend some time learning about real-world processes. At least read Ullmann's Encyclopedia of Industrial Chemistry or something similar. In the real world, catalysts do get used up, and frequently even entrained to varying degrees into the product. In fact, it's relatively rare that a catalyst lasts indefinitely (there are some processes where the catalyst does, but most do not). Some processes have a relatively simple step to renew their catalysts. Others require complete replacement of their catalysts with newly produced ones. Sometimes the catalyst is lost by design.
The way in which catalysts become "used up" varies greatly. Sometimes, analogous to your "concrete", it's lost by design into the product stream, such as with most plastics polymerization. So for example, with polyethylene, you may get something like 5000 grams of PE per gram of catalyst, but then the catalyst is gone. Usually there's no recovery step. In some processes, catalysts are lost by being poisoned, either by impurities or by side reactions. Catalysts can be "gunked up" and lose their reactive surface area - for example, by coking in petrochemical refining. Catalysts can also erode - for example, in the Ostwald process for making nitric acid, there's almost always a catalyst recovery stage downstream, because platinum and rhodium are very expensive, and erosion rates are high. Even the process of erosion varies - for example, in some cases it might be substrate attack, or active surface attack, or formation of dendrites which break off, or all sorts of things.
In general, in industry you call it a catalyst if it catalyzes a significant number of reactions, rather than being used up in the first reaction (the latter being considered a feedstock). There is no requirement that it be able to catalyze an infinite number of reactions. Technically things which catalyze a "small number" of reactions should be called initiators, and those which catalyze a "large number" should be called catalysts, but the distinction isn't always clear, and the language overlaps.
Stale pastry is hollow succor to one who is bereft of ostrich.
According to the paper, all CO2 generated by the photooxidation of lignocellulose enters the basic solution as carbonate ions. So it's up to you as to what you want to do with them after that - industrial feedstocks, reaction and sequestration, or even simple exhaustion as CO2, with the knowledge that at least it's a closed fuel cycle (CO2 taken in during growth being released back to the air).
It's a shame that the process doesn't generate CO rather than CO2. CO + H2 = syngas = great source for synfuels and other petroleum products (CO is relatively stable at normal temperatures and pressures but highly reactive at elevated temperatures and pressures, to the point of even spontaneously breaking down to C + CO2 - so when you have hydrogen in the mix, you have the stage set for the formation of hydrocarbons of varying lengths depending on your environmental conditions). Of course, I guess if they wanted syngas they'd just partially oxidize the lignocellulose directly under heat. In fact, as the paper mentions, that what's already done in biomass gasifiers. They just want the hydrogen.
Stale pastry is hollow succor to one who is bereft of ostrich.