| Summary: | Porous carbon was synthesized from coffee waste for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). The coffee waste was carbonized at 600 °C for 2 hrs and activated at 500, 600, and 700 °C, respectively. The activated coffee waste at 600 °C exhibits lower overpotential of -210 mV at -10 mA cm−2 and 230 mV at 10 mA cm−2 with lower Tafel slopes of 120 mV dec−1 and 140 mV dec−1 for HER and OER, respectively, compared to the samples at different activated temperature. The better HER and OER performances are associated to high electroactive surface area (3.9 × 10−5 cm2) and low charge transfer resistance (39 Ω) of the 600 °C activated sample, which also shows interconnected porous structure, in comparison with the other samples. The coffee waste after the carbonization and activation could be applied for HER and OER electrocatalyst.
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