Solar panel waste silver turned into catalyst for carbon monoxide production

Researchers in South Korea have developed a new method to upcycle high-purity silver nanoparticles recovered from end-of-life silicon solar panels into electrocatalysts for high-rate carbon monoxide (CO) production. CO is an important industrial feedstock used in the production of chemicals and fuels, including methanol, acetic acid and synthetic hydrocarbons.

The recovered silver formed a rough catalyst surface that helped prevent flooding inside the electrolyzer, allowing it to sustain CO production for more than 600 hours.

“This work highlights that upcycled photovoltaic waste can serve as a highly durable and scalable alternative to resource-intensive commercial catalysts, pushing forward the practical implementation of sustainable carbon dioxide (CO₂) conversion,” the academics said. “This work underscores the potential of integrating electronic waste valorization with electrocatalytic carbon utilization.”

The researchers collected end-of-life silicon solar panels and mechanically processed them using a commercial separation system operated by Reset Company. After removing the aluminum frames, tempered glass and backsheets, they heated the remaining solar cell fragments to 800 C to decompose the ethylene-vinyl acetate (EVA) encapsulant.

They then immersed the fragments in nitric acid, dissolving the metals and separating the silicon residue. In a first alkaline treatment, they precipitated impurities including copper, aluminum and lead. A second alkaline treatment precipitated the silver as silver oxide.

The team then dispersed the silver oxide in ethanol with stearic acid and applied laser irradiation to reduce it to metallic silver nanoparticles. The researchers mixed the recovered particles with a Nafion ionomer solution and isopropanol before spray-coating the ink onto a carbon gas diffusion layer at 70 C.

Using the same preparation method and a target silver loading of 1 mg/cm², they fabricated a comparison electrode from commercial silver nanoparticles. Both electrodes were tested in a 10 cm² zero-gap membrane electrode assembly (MEA) electrolyzer, with a potassium bicarbonate solution circulating on the anode side and CO₂ supplied to the cathode.

The researchers used microscopy and chemical analyses to examine the particles’ size, shape, crystal structure and purity, and then compared the surfaces of the two coated electrodes. In the electrolyzer, they measured CO production and selectivity at increasing current densities and conducted extended tests to assess durability.

They also measured how strongly water droplets and CO₂ bubbles adhered to each electrode. Finally, they used a transparent electrolyzer to observe liquid entering the gas diffusion layers during operation, allowing them to compare the electrodes’ resistance to flooding.

“Physical characterizations and surface analyses revealed that the hydrometallurgical recovery coupled with laser photoreduction naturally creates a highly crystalline metallic Ag state with a unique, multi-scale nano-to-micro morphological distribution,” the researchers said. “While this hierarchical polydispersity induces a minor trade-off in the initial electrochemical active surface area (ECSA) compared to uniform commercial counterparts, it acts as a critical structural asset during high-rate MEA operations.”

According to the results, the end-of-life silver (EoL-Ag) gas diffusion electrode demonstrated high flooding tolerance, sustaining continuous, stable CO₂ electrolysis in a 10 cm² zero-gap cell for more than 600 hours at 100 mA/cm². It also operated for 55 hours at an industrially relevant current density of 200 mA/cm², while maintaining CO selectivity of around 95%.

The article “Upcycling photovoltaic silver waste into hierarchically structured electrocatalysts for flooding-resistant zero-gap CO2-to-CO electrolysis” was published in the Journal of CO2 Utilization.

Researchers from South Korea’s Korea Institute of Science and Technology (KIST), RESET Company, Sungkyunkwan University (SKKU), Korea University of Science and Technology (UST) and Yonsei University contributed to the study.

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