Renewable energy is a vital element of a low-carbon future, but because sources such as wind and solar don’t always generate electricity when it’s needed, efficient energy-storage systems are essential.

Khalifa University researchers say they’re developing a material for fabricating high-performance supercapacitor electrodes that has the added benefit of reusing waste from industries such as wastewater treatment and biofuel production.

In a paper in Environmental Technology & Innovation, the researchers describe how they converted the microscopic algae Dunaliella salina into biochar, a carbon-rich material produced by heating biomass without oxygen, and used it to create an electrode for a supercapacitor. Supercapacitors can charge and release energy much faster than conventional batteries.

The biochar electrode showed strong energy-storage performance, reaching a specific capacitance of 507.9 farads per gram. It also retained 104 percent of its original capacitance after 2,000 charge-discharge cycles. The slight increase is thought to result from repeated cycling opening up previously inaccessible areas of the material to the electrolyte.

Unlike many biochar-based electrodes, the material did not require chemical activation, added conductive materials or binding agents. Instead, the researchers deposited the algae-derived biochar directly onto nickel foam. This simpler process could make the technology less expensive and more environmentally friendly while giving new value to waste left over from algae-based industries.

Computer simulations helped explain the material’s performance. The researchers found that nitrogen- and oxygen-containing chemical groups naturally present in the biochar create favorable sites for potassium ions to attach and exchange charge. These interactions could help the electrode store and release energy quickly and efficiently.

Although the electrode still needs to be tested more, the research points to a potential way to turn biological waste into low-cost materials for fast-charging energy systems.

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