Electrocatalytic generation of hydrogen peroxide on cobalt nanoparticles embedded in nitrogen-doped carbon

Electrocatalytic reduction of oxygen is a growing synthetic technique for the sustainable production of hydrogen peroxide (H2O2). The current challenges concern seeking low-cost, highly active, and selective electrocatalysts. Cobalt-nitrogen-doped carbon containing catalytically active cobalt-nitrogen (Co-N-x) sites is an emerging class of materials that can promote the electrochemical generation of H2O2. Here, we report a straightforward method for the preparation of cobalt-nitrogen-doped carbon composed of a number of Co-N-x moieties using low-energy dry-state ball milling, followed by controlled pyrolysis. This scalable method uses inexpensive materials containing cobalt acetate, 2-methylimidazole, and Ketjenblack EC-600JD as the metal, nitrogen, and carbon precursors, respectively. Electrochemical measurements in an acidic medium show the present material exhibits a significant increase in the oxygen reduction reaction current density, accompanied by shifting the onset potential into the positive direction. The current catalyst has also demonstrated an approximate 90 % selectivity towards H2O2 across a wide range of potential. The H2O2 production rate, as measured by H2O2 bulk electrolysis, has reached 100 mmol g(cat.)(-1) h(-1) with high H2O2 faradaic efficiency close to 85% (for 2 h at 0.3 V vs. RHE). Lastly, the catalyst durability has been tested (for 6 h at 0.3 V vs. RHE). The catalyst has shown relatively consistent performance, while the overall faradic efficiency reaches approximate 85% throughout the test cycle indicating the promising catalyst durability for practical applications. The formed Co-N-x moieties, along with other parameters, including the acidic environment and the applied potential, likely are the primary reasons for such high activity and selectivity to H2O2 production. (c) 2021, Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.