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 °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∥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.