Activated carbon from waste fabrics as a catalyst for NaBH4 methanolysis

Abstract

Hydrogen energy is attractive as a sustainable and clean energy. Chemical hydrides are being studied as a solution to the transportation and storage problems of hydrogen. Hydrogen can be produced by methanolysis reaction of sodium borohydride on a suitable catalyst. For this purpose, metal catalysts with high catalytic activity are generally used. Despite their high catalytic activity, the environmental impact and cost of metal-containing catalysts has led to increased interest in synthesizing metal-free catalysts. Activated carbons are advantageous materials for metal-free catalyst applications. In recent years, industrial wastes have attracted much attention for the synthesis of sustainable materials for activated carbon preparation. In this study, activated carbons are produced from waste fabrics by chemical activation method using H3PO4 and KOH chemical agents at different impregnation ratios (1:1, 2:1 and 3:1 % w:w) and different carbonization temperatures (400, 500, 600°C for H3PO4 and 600, 700, 800°C for KOH). These carbons are used as catalysts for hydrogen production and their catalytic activity is evaluated based on hydrogen generation rate (HGR). Therefore, the effect of different conditions used in the preparation of activated carbon was investigated to determine its impact on HGR. The increase in carbonization temperature decreases the HGR value of the catalyst. The increase in acid concentration increases the HGR value. The highest HGR value is obtained as 39600 mL/(min.gcat) with YKK1–800 activated carbon. Once the carbon with high activity is identified, the effect of reaction conditions such as NaBH4, methanol, catalyst amount, and temperature on HGR is investigated. The catalytic activities of the prepared activated carbons in NaBH4 electrooxidation are also investigated. YKK3–700 activated carbon shows the highest catalytic activity at 1.91 mA/cm2 at −0.63 V peak potential. This result is promising for the use of metal-free catalysts for direct sodium borohydride fuel cells.