Ternary doping of phosphorus, nitrogen, and sulfur into porous carbon for enhancing electrocatalytic oxygen reduction

We report a synthesis of phosphorus (P), nitrogen (N) and sulfur (S) ternary co-doped porous carbon (PNS-PC) which acts as efficient metal-free electrocatalyst for the ORR. PNS-PC has been fabricated via an electrostatic assembly method followed by a carbonization process. Tetraphenylphosphonium bromide is employed as carbon and phosphorus source and ammonium persulfate as nitrogen and sulfur source. The as-prepared PNS-PC possesses high BET specific surface area (>580 m(2) g(-1)). The most active PNS-PC that containing 1.44 at.% P, 2.96 at.% N and 2.65 at.% S exhibits much enhanced electrocatalytic activity for the ORR compared to solely P-doped carbon (P-C) in alkaline media. This PNS-PC shows an onset potential of 0.905 V (vs. RHE), which is 120 mV higher than that of P-C. A negative shift of only about 68 mV in the half-wave potential of the PNS-PC as compared to commercial Pt/C (20 wt.% Pt on Vulcan XC-72, Johnson Matthey) is achieved. The high electrocatalytic activity of the PNS-PC is primarily attributed to the synergistic effect of P, N and S ternary doping in carbon and its hierarchical porous structure. The results demonstrate that multiple element doping is an efficient way for enhancing the electrocatalytic activity of carbon for ORR. (C) 2015 Elsevier Ltd. All rights reserved.