Bio-derived nanoporous activated carbon sheets as electrocatalyst for enhanced electrochemical water splitting

Designing highly efficient and durable metal-free electro-catalysts replacing the precious (non)noble metals is crucial to the future hydrogen economy and various renewable energy conversion and storage devices. Herein, we report an efficient low-cost nanoporous activated carbon sheets (NACS) with hierarchical pore architecture from Indian Ooty Varkey (IOV) food waste for oxygen evolution (OER) and hydrogen evolution reactions (HER) by following "waste to wealth creation" strategy. Characterization of NACS carbo-catalyst reveals the presence of pyridinic-nitrogen inherited by self-doping of N from the biomass with high BET surface area (1478.0 m2 g-1). As an electrocatalyst in alkaline medium, it exhibits low-onset potential (1.36 V vs. RHE), an overpotential (η10) of 0.34 V at 10.0 mA cm−2 with a small Tafel value (43 mV dec−1), and good stability towards OER compared to Pt or Ir commercial catalysts. Tested as HER catalyst, it displays an impressive HER activity with a low-onset potential of −0.085 V (vs. RHE), and overpotential (η10) of 0.38 V at 10.0 mA cm−2 with a small Tafel slope of 85 mV dec−1.