Steam-Activated High Specific Surface Area of Bio-derived Porous Carbon as Sustainable Metal-Free Electrocatalyst for Hydrogen Evolution Application

Abstract

Bio-derived materials can serve as effective alternatives to the high costs associated with traditional electrocatalysts for hydrogen evolution reaction (HER). In this study, a facile and environmentally benign approach was employed to synthesize nitrogen self-doped pecan shell-derived steam-activated porous carbon (N-PSAPC). The steam activation process considerably alters the surface properties of the carbon materials, specifically defect and porosity. Among different temperatures, the high specific surface area (879 m2/g) and pore volume (0.48 cm3 g−1) attained steam activation at 700 ℃. Steam generates hydroxyl radicals and hydrogen, which react with carbon to form internal pores, increasing surface area. Multi-walled carbon nanotubes were added as conductive agents for the electrode materials. The resulting N-PSAPC catalyst shows excellent HER performances with a low overpotential of 141.4 mV at 10 mA cm−2 in alkaline media and exhibits outstanding cycle performance after 5000 CV cycles. The lower charge transfer resistance and improved electrochemically active surface area (Cdl = 90.41 mFcm−2) of N-PSAPC-700 is the key reason for attaining the efficient electrocatalytic activity. As a cathode for overall water splitting, it achieves a cell voltage of 1.62 V at 10 mAcm−2. This work highlights steam activation as an effective, environmentally friendly approach for producing high-performance of metal-free HER electrocatalysts.