Low-loading Ir decorated cobalt encapsulated N-doped carbon nanotubes/porous carbon sheet implements efficient hydrogen/oxygen trifunctional electrocatalysis

Development of cost-efficeint and high activity muli-functional catalysts for gas-involved reactions such as Oxygen reduction evolution (ORR), oxygen evolution reaction (OER) and hydrogen evolution recation reaction (HER) is desirable but challenging. Herein, low-loading of Iridium (Ir) (≈2.3 wt%) decorated cobalt nanoparticles embedded in nitrogen-doped carbon nanotube/porous carbon sheets ([email protected]/PC) is prepared to serve as the OER/HER/ORR trifunctional electrocatalyst. The resulting composites demonstrate excellent OER and HER activity in both acidic and alkaline electrolytes, including low overpotentials at 10 mA cm−2 (η10) for OER (about 291 and 240 mV) and HER (about 26.8 and 37 mV), respectively, which are superior to the benchmarking Pt/C and IrO2 catalysts. Hence, low cell voltages of 1.51 and 1.45 V are required at j = 10 mA cm−2 (j10) for overall water splitting (OWS) in the acidic and alkaline electrolytes, respectively. In addition, the as-prepared [email protected]/PC also shows efficient ORR performance with a high half-wave potential (E1/2) of 0.83 V vs. RHE. It is then used as the air cathode for rechargeable Zn-air battery (r-ZAB), and exhibits an outstanding specific capacity (810 mAh g−1), low charge-discharge polarization (ΔE = 0.896 V at j = 50 mA cm−2) and long cycling performance (increased only 0.15 V after 195 cycles).