Construction of MWNT supported ultra-small Ag@MnO₂ nanoparticles for the ORR and Al-air batteries

The development of non-platinum catalysts for high efficiency oxygen reduction reaction (ORR) is one of the research hotspots of fuel cells and metal air cells. In this work, a low-cost Ag@MnO2/MWNT catalyst for Al-air batteries was synthesized in one step by using tetrakis(hydroxylmethyl)phosphonium chloride (THPC) as a reducing agent. Ag was attached to the surface of MnO2 to form Ag@MnO2 nanoparticles with an average particle size of 4.88 nm, which were uniformly deposited on MWNTs. The Ag@MnO2/MWNT catalyst has a low Ag load (10.03 wt%) and shows excellent ORR activity, electrochemical stability and methanol tolerance compared with the 20 wt% Pt/C catalyst. The discharge voltage, specific capacity (1240 mA h g(-1)), the power density (140.2 mW cm(-2)) and stability of the Al-air battery using Ag@MnO2/MWNTs as the cathode are equivalent to those of a battery using 20 wt% Pt/C.