Plastic is everywhere. Tens of millions of tons of plastic are released into the environment every year. Plastic accumulates in the human body and may be associated with cardiovascular and neurological diseases such as dementia. It even contaminated the rain. Despite these serious concerns, plastic is not going anywhere. Plastic waste is expected to almost triple by 2060 without major policy changes. A new solution could solve two problems by turning unwanted plastic into valuable green hydrogen.
Cambridge researchers have developed a solar-powered system that takes polyethylene terephthalate (PET) bottles, often used for water bottles, and emits hydrogen and other useful chemicals. First, the plastic is crushed into small pieces, mixed with potassium hydroxide and heated to 176 degrees Fahrenheit for three days. This breaks down PET, releasing ethylene glycol, one of its building blocks. The researchers then filter out any remaining PET and feed the liquid solution into the solar panel’s reactor.
These solar panels do not produce electricity. They produce a chemical reaction called photoreforming. A photocatalyst coating absorbs sunlight and uses it to produce hydrogen. The researchers first tested small panels, then built a 10.8-square-foot outdoor reactor made up of four larger panels. A follow-up test using PET showed that the same basic process could produce hydrogen on a larger scale.
The hydrogen problem this solar panel breakthrough could solve
Hydrogen is currently in high demand. It is used to refine petroleum and produce steel, methanol and ammonia. Yet only about 1% of global production is low-emission hydrogen. Most of it is based on fossil fuels, including in the United States, which generates almost all of its hydrogen by breaking down natural gas, releasing a huge amount of CO.2 in the atmosphere. Being able to produce green hydrogen without emissions would significantly reduce the carbon footprint created by its demand.
Industry leaders see the benefit of switching to hydrogen if it becomes commercially viable. The problem is that green hydrogen is difficult to produce, so scientists are working to make it more practical. Water electrolysis is one approach. It uses electricity to split water into hydrogen and oxygen. The Cambridge team says that splitting water takes a lot of energy and some of the reaction happens slowly. Breaking down plastic is another option, typically using heat to release hydrogen. The team says this requires a lot of energy and can be difficult to control what is produced.
To reduce costs and improve stability, researchers say they will need to figure out how to capture more sunlight, how to absorb more visible light, and how to make photocatalysts last longer. They know chemistry works. They want this to happen on a larger scale. There’s also a dangling thread they might be able to pull: a solar panel that generates electricity while turning plastic into hydrogen. The device under test only absorbs UV light, which could leave the rest of the spectrum producing electricity. The researchers haven’t said whether they will actively explore it.
