Carbonized Hemoglobin Functioning as a Cathode Catalyst for Polymer Electrolyte Fuel Cells

Abstract

Raw materials for producing polymer electrolyte fuel cells should be inexpensive and abundant in their resource in order to widely substitute this new energy system for conventional ones. In this study, a catalyst for the cathodic oxygen reduction was formed from hemoglobin, a large amount of which would be always available. The heat treatment in an inert atmosphere around 800°C produced a carbonized material with highly developed nanospaces. The specific surface area reached 1005 m 2 g -1 at the optimized carbonization conditions. The fundamental electrochemical properties were evaluated using rotating disk electrodes, forming a catalyst layer from the carbonized material with the polymer electrolyte on the electrode surface and immersing the layer in oxygen-saturated perchloric acid. We found that the carbonized materials were active toward oxygen reduction and the activity increased with the nanospace development, essential for exposing the active sites on the pore surface. The oxygen reduction behavior reflected the pore structure and iron content. A preliminary fuel cell test using the material in the cathode confirmed the current generation. Although the performance was inferior to a Pt-based fuel cell, the result suggested that it could be improved by structure modification and surface treatment of the material.

Carbonized Hemoglobin Nanofibers for Enhanced H2O2 Detection

“…The Fe 2p 3/2 peak located at 710.6 eV and Fe 2p 1/2 located at 723.1 eV were observed which can be attributed to Fe 2 O 3 on the surface of Hb-CNFs. The XPS result is in good agreement with the reported values [37,40]. Besides Hb-CNFs due to the pyrolysis of the Fe(III) porphyrin even though there is no direct evidence to support the presence of Fe-N 4 moiety [37].…”

“…After carbonization in Ar atmosphere at 800 8C for 2 h, carbon nanofibers (denoted as Hb-CNFs) were formed from Hb microbelts precursors with the average diameter in several hundred nanometers range, but still kept a continuous and porous pattern ( Figure 1B). In addition, as shown in Figure 2A, the surface of Hb-CNFs is rough and decorated with a number of small Fe 2 O 3 particles with a diameter at tens nm level, which were formed due to the decomposition of Fe(III) porphyrin in Hb and combination of Fe and oxygen from the polypeptide chain in Hb [37]. In TEM image, the amorphous carbon appears as the gray area and Fe 2 O 3 particles appear as the black dots.…”

“…Polyacrylonitrile (PAN) is the most commonly used precursor to fabricate electrospun fibers in the range of hundred nanometers and the subsequently pyrolyzed CNFs have a diameter ranging from several ten to several hundred nanometers [33 -35]. Besides the traditional polymers, some proteins such as hemoglobin (Hb) have been recently reported as the carbon precursors [36,37]. Hb is a tetrameric protein consisting of four subunits and each subunit is a combination of a polypeptide chain and a heme.…”

“…The heme consists of an iron atom (Fe 2þ or Fe 3þ ) attached to a planar organic structure belonging to porphyrin compounds. Heat treatment of Hb powder in Ar atmosphere at high temperature produced carbonized materials containing Fe species (Fe 2 O 3 and/or Fe-N 4 moiety) [37].…”

The structural changes of blood pyropolymers and their beneficial electrocatalytic activity toward oxygen reduction

“…The animal blood proteins are abundantly available and inexpensive; especially the pig blood protein, being from the meat industry that produces more than 200 million tons of meat every year worldwide, is thrown away as waste [19]. The animal bloods, including huge amounts of different bioproteins such as hemoglobin and myoglobin, should be thoroughly investigated due to their potential for preparing the ORR catalyst.…”