Trace Level Co-N Doped Graphite Foams as High-Performance Self-Standing Electrocatalytic Electrodes for Hydrogen and Oxygen Evolution

The development of eco-friendly electrocatalysts with high performance and low cost for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is significant for renewable energy storage. Here, trace level (0.11-0.18 wt %) Co-N doped graphite foam (Co-N/GF) was reported to work as a bifunctional high-performance and self-standing electrode for both HER and OER in alkaline electrolyte. The catalytic activities of Co-N/GFs with different annealing temperatures (600, 700, 800, 900, and 1000 degrees C) were carefully studied. Among them, Co-N/GF-900 exhibited the best HER activity and Co-N/GF-700 showed the best OER activity, achieving the current density of 10 mA cm(-2) at low overpotentials of 165 and 313 mV, respectively. In addition, both of these electrodes exhibited long-term durability. Co-N/GF electrodes were further constructed as a catalytic cathode and anode couple (Co-N/GF-900 parallel to Co-N/GF-700) for overall water splitting, exhibiting a low cell voltage of 1.68 V and good long-term stability. Our work reveals that introducing a trace level of Co-N into graphite foam can significantly enhance its electrocatalytic activity and stability for both HER and OER