Interconnected hierarchical nanoarchitectonics of porous carbon nanosheets derived from renewable biomass for efficient oxygen evolution reaction

Developing highly active, low-cost, earth-abundant, and eco-friendly metal-free electrocatalysts is a significant challenge for oxygen evolution reaction (OER) applications. In this study, we have demonstrated a simple, inexpensive, and economical approach to synthesize interconnected hierarchical porous carbon nanosheets (HPCNS) from renewable biomass for efficient OER applications. The synthesized HPCNS product exhibited high nitrogen content (5.02%), high surface area (up to 2954 m2 g−1), and high conductivity (up to 11.03 S cm−1). The obtained HPCNS exhibited excellent OER performance with low overpotential (106 mV) at a current density of 10 mA cm−2 in 1 M KOH electrolyte compared to that of commercial RuO2, indicating outstanding charge transfer ability compared to the other two electrodes, HPCNS-600 (379 mV dec−1) and HPCNS-700 (208 mV dec−1). Among the different HPCNS samples, HPCNS-700 exhibited the lowest charge transfer resistance (Rct) value (2.3 Ω); therefore, HPCNS-700 demonstrated the best OER activity. Furthermore, the prepared HPCNS samples exhibited high electrochemically active surface areas (ECSA) and double-layer capacitances (Cdl). The effective surface areas of HPCNS-600, HPCNS-700, and HPCNS-800 were observed to be 1.72 cm−2, 3.75 cm−2 and 1.87 cm−2, respectively. The HPCNS-700 electrode had the highest Cdl value (0.303 mF), which indicated more catalytically active sites for OER applications compared to the other two samples. Thus, herein we report a potential method for fabricating metal-free electrocatalysts for OER applications, which are comparable to state-of-the-art ruthenium-based benchmark commercial catalysts and other carbon-based materials. This remarkable performance of HPCNS electrocatalysts indicates great effectiveness for future applications.