Abstract
On average, 0.5 mg/cm2 of platinum is used in Membrane Electrode Assembly (MEA), a key material of the fuel cell, and research is being conducted to replace platinum with cheap materials or reduce the amount used in order to reduce the production cost. Most Pt/C catalysts are composed of more than 99% of graphite, and in the form of a film, they must maintain a moisture content within a specific range because they act as catalysts for protons to flow through water in polymer fuel cells. It is known that in a general hydrometallurgical process for recovering platinum from spent MEA, about 90% or more of platinum is retrieved by using hydrochloric acid and hydrogen peroxide as an oxidizing agent by selecting the MEA by chemical or physical treatment after disassembling the defective stack.
This study investigated the effect of Pt/C converted through oxygen-free heat treatment on platinum leaching from spent polymer electrolyte membrane fuel cell (PEMFC). The temperature was set based on the inflection point of the weight by the DTA/TG experiment. Around 65% of Pt leached out in the untreated samples at 6M hydrochloric acid, 5 g/L pulp density, agitation 250 rpm, and room temperature. As the temperature increased to 600 ℃, Pt leached more than 95% whereas the leaching reaction slowed down at 1000 ℃. Because Pt in the Pt/C catalyst converted to platinum oxide during high-temperature heat treatment. ICP, XPS, and TEM analyses were investigated to confirm the changes of Pt/C catalyst before and after leaching heated and unheated samples. As a result, leaching efficiency was affected by the conversion of the catalyst phase through heat treatment.