Phosphorous-Doped Graphite Layers with Outstanding Electrocatalytic Activities for the Oxygen and Hydrogen Evolution Reactions in Water Electrolysis

Advances demonstrate that the incorporation of phosphorous into the network of nitrogen, sulfur, or fluorine-doped carbon materials can remarkably enhance their oxygen and hydrogen evolution activities. However, the electrocatalytic behaviors of pristine phosphorous single-doped carbon catalysts toward the oxygen and hydrogen evolution reactions (OER and HER) are rarely investigated and their corresponding active species are not yet explored. To clearly ascertain the effects of phosphorous doping on the OER and HER and identify the active sites, herein, phosphorous unitary-doped graphite layers with different phosphorous species distributions are prepared and the correlations between the oxygen or hydrogen evolution activity and different phosphorous species are investigated, respectively. Results indicate that phosphorous single-doped graphite layers show a superior oxygen evolution activity to most of the reported OER catalysts and the commercial IrO2 in alkaline medium, and comparable hydrogen evolution activity to most reported carbon catalysts in acidic medium. Moreover, the relevancies unveil that the C-O-P species are the main OER active species, and the defects derived from the decomposition of C-3-P = O species are the main active sites for HER, as evidenced by density functional theory calculations, showing a new perspective for the design of more effective phosphorous-containing water-splitting catalysts.