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M a n g a n e s e o x i d e -m o d i f i e d g r a p h e n e nanosheet-supported silver nanocatalyst (Ag-MnO x /G) was prepared via two-step chemical and electrochemical deposition. Surface characterization of the prepared AgMnO x /G catalyst was performed by X-ray photoelectron spectroscopy, scanning electron microscopy, as well as Xray fluorescence techniques, and the electrocatalytic activity toward the oxygen reduction reaction (ORR) in alkaline media was studied using cyclic voltammetry and the rotating disk electrode (RDE) method. The onset potential of the ORR of the prepared catalyst material shifted positive about 40 mV, and the half-wave potential 20 mV compared to those of the bulk Ag electrode. After 1000 potential cycles between 0.05 and 1.1 V for accelerated aging tests, high stability of the Ag-MnO x /G catalyst in the ORR was observed with the half-wave potential of the ORR shifting negatively only about 0.04 V. RDE studies displayed unconditional improvement of electrochemical activity and long-term durability for the Ag-MnO x /G composite material.

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In this work, PdPt alloy nanocubes with different metal ratios were synthesised in the presence of polyvinylpyrrolidone (PVP). The surface morphology of the PdPt samples was characterised by transmission electron microscopy (TEM). TEM images showed that PdPt nanoparticles were cubic-shaped and the average size of the cubes was about 8-10 nm. Their electrocatalytic activity towards the oxygen reduction reaction (ORR) was studied in 0.5 M H 2 SO 4 using the rotating disk electrode method. All the alloyed catalysts showed enhanced electrocatalytic activity for ORR as compared to the monometallic cubic Pd nanoparticles.Half-wave potential values for PdPt catalysts were comparable with that of Pt nanocubes.From the alloyed catalysts Pd 36 Pt 64 exhibited the highest specific activity, which was only slightly lower than that of cubic Pt nanoparticles. The Koutecky-Levich analysis revealed that the reduction of oxygen proceeded via 4-electron pathway on all the electrocatalysts studied.

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