Electrochemical reduction of oxygen in alkaline solution on Pd/C catalysts prepared by electrodeposition on various carbon nanomaterials

Electrochemical deposition by applying potential steps between - 0.25 (or 0 V) and 0.85 V (vs SCE) was used to deposit Pd on different nanocarbon substrates. Influence of over potential on the electrodeposition process was observed. Obtained Pd/C catalysts were studied with scanning electron microscopy and electrochemically in alkaline solution. Specific activity for the oxygen reduction reaction (ORR) of the catalysts was determined using the rotating disc electrode method. The ORR on all the studied Pd/C catalysts proceeded through a 4-electron pathway with a rate-limiting step of the first electron transfer to the O-2 molecule. Pd catalysts deposited on graphene nanosheets showed highest specific activities for the ORR. The prepared catalysts showed higher specific activities than commercial Pd/C catalysts, which can be due to electrodeposition process proceeding without the presence of intrusive additives used in chemical synthesis of nanoparticles. Electrochemical activation was employed to improve the electrocatalytic activity of carbon nanotube-supported Pd catalysts for ORR.