Hemoglobin Pyropolymer Used as a Precursor of a Noble-Metal-Free Fuel Cell Cathode Catalyst

Abstract

The partial pyrolysis of hemoglobin yielded the hemoglobin pyropolymer, which is an intermediate substance between a polymer and carbonaceous material. The pyropolymer was formed by the heat treatment of hemoglobin below 600°C. The formation behavior of the pyropolymer was examined by thermogravimetry and differential thermal analysis, and the pyropolymer was characterized by elemental analysis and its 13 C nuclear magnetic resonance spectrum. The pyropolymer formation began around 200°C, and aromatic carbon developed with an increase in the heat-treatment temperature through transformation of the aliphatic carbon in hemoglobin. A noble-metal-free cathode catalyst for a polymer electrolyte fuel cell (PEFC) was formed by heat treatment of the hemoglobin pyropolymer in flowing Ar containing 10% CO 2 . The activity of the catalyst was dependent on the characteristics of the pyropolymer. The carbon matrix developed with an increase in the aromatic carbon, whereas the micropore development was suppressed. The highest activity was observed for the catalyst with the maximized micropore development. The PEFC using the catalyst with the highest activity obtained in this study generated 0.12 and 0.23 W cm -2 at O 2 partial pressures of 54 and 254 kPa, respectively. Continuous PEFC operations and measurements of the extended X-ray absorption fine structures demonstrated that the current decrease during the operation correlated with the structure of the active site of the catalyst.

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

“…However, it is convinced that the formation of several weak endothermal peaks displaying on the DTA curve as well as a weight loss of about 45.2% on the TGA curve might be mainly attribute to the decomposition of various amino acids within the PB. Based on the previous reports, it is anticipated that the carbonized procedure of single bioprotein is accomplished at about 500°C and the internal structure of low-temperature carbon materials absolutely shifts from the aliphatic to the aromatic carbon checked by 13 C NMR spectra [22]. For this reason, here a reasonable speculation is put forward that the formation process of PB pyropolymer will be completed at 500°C.…”

“…It is necessary to investigate the carbonization behavior of various proteins. Maruyama et al [22] reported the two-step carbonization process of hemoglobin from bovine blood in 2008. The substance prepared in the first heat-treatment step was designated as a precursor for the catalyst.…”

“…The substance prepared in the first heat-treatment step was designated as a precursor for the catalyst. Most recently, it has been recognized that the substance obtained by thermal treatment of a polymer material below 600°C is usually an intermediate between the polymer and carbon material because of its incomplete carbonaceous phase generation and could be called a pyropolymer [22]. However, the pyropolymer has not yet been studied in detail because its structure is extremely complex.…”

The Role of Nanostructure in Improving the Performance of Electrodes for Energy Storage and Conversion

“…This function should promote the LTWGS reaction at the anode and the DHP reaction at the cathode. In fact, excellent progress has been made on noble-metal-free electrodes for fuel cells, [205][206][207][208] but still high-performance and stable electrodes are based on Pt.…”

Synthesis–structure–performance correlation for poly(phenylenediamine)s/iron/carbon non-precious metal catalysts for oxygen reduction reaction

“…However, some fundamental researches of M N C are often ignored, such as exploring the structure-performance relationship and revealing the active sites. Jasinski has reported that a N 4 -chelate complex with a non-noble metal could be used to electrochemically reduce oxygen in 1964 [13], and following this many macrocyclic transition-metal compounds including of porphyrins, phthalocyanines, and tetraazaannulenes [14][15][16], have been investigated with respect to ORR activity. It has been widely accepted that active sites of ORR in acid solution are M N x in these catalysts [17][18][19].…”