Tree‐Bark‐Shaped N‐Doped Porous Carbon Anode for Hydrazine Fuel Cells

Abstract

Metal-free N-doped porous carbon has great potential as ac atalyst for hydrazine oxidation in direct hydrazine fuel cells (DHFCs). However,p revious studies have reported only half-cell characterization, and the effect of the pore sizedistribution has not been intensively investigated. Herein, we report the synthesis of highly active,m etal-free Ndoped carbon (NDC) by controlling the pore sizedistribution, and for the first time,the effect of the pore size distribution on the anode performance in aDHFC is investigated. As aresult, tree-bark-shaped NDC with meso/macroporous (> 10 nm) structures exhibit ar emarkable power density of 127.5 mW cm À2 in aDHFC.Recently,the demand for renewable and clean energy sources has gradually increased owing to the exhaustion of fossil fuels accompanied by an umber of environmental problems.A sa ne ffort to use alternative energy sources, various kinds of energy conversion systems have been developed. Forinstance,Evans and Kordesch [1] first suggested the concept of adirect hydrazine fuel cells (DHFC) system in the 1960s,w hich eventually attracted substantial attention because of its advantages as an anode:1 )the high energy density of hydrazine,2)ahigh theoretical cell potential, 3) the absence of platinum-group metals,and 4) zero CO 2 emissions. Because of these advantages,anumber of studies have been reported on developing catalysts for the oxidation of hydrazine. [2][3][4][5][6][7][8][9][10][11] Since Asazawa et al. [2] unveiled that noble-metalfree catalysts,N ia nd Co,e xhibit higher activities toward hydrazine oxidation than Pt in DHFCs,most of the studies on DHFCs have focused on the development and characterization of noble-metal-free catalysts over the last few decade. Recently,M eng et al. [6] developed am etal-free catalyst, polypyrrole-derived Na nd Oc o-doped mesoporous carbon, for the hydrazine oxidation reaction (HDOR), but there has not been ar eport on its fuel-cell performance so far.

Optimistic performance of carbon-free hydrazine fuel cells based on controlled electrode structure and water management

“…Because the carbon support also showed an activity for the HDOR at this region, the activity of straight-line shape region would be from the carbon. A previous study, which has reported the activities of metal-free carbon materials used for HDOR, supports our suggestion that the straight-line shape region is an irrelevance to Ni properties, because the onset potential for the HDOR on metal-free carbon in LSV is consistent with that observed in our straight-line shape region [30] . Consequently, the 45 wt% Ni/C catalyst shows the best HDOR activity among the as-prepared catalysts.…”

Carbon Electrocatalysts For Hydrazine Oxidation: Self-Templating Design Of Hierarchical Porosity Using Barium Carbonate Nanoparticles

“…This potential represents a lower overpotential for the HzOR, as compared to previous metal-free carbons at the same pH range, reported to be 0.4-0.6 V vs RHE at pH 14. 27,28 The HzOR efficiency of doped carbon catalysts derived from alkaline earth metal-based precursors is linked with their superior microstructure. 12,28 In contrast, carbons pyrolyzed at lower temperatures performed worse, with lower onset potentials (as positive as 0.79 V vs RHE for C-500) and lower current densities.…”

“…27,28 The HzOR efficiency of doped carbon catalysts derived from alkaline earth metal-based precursors is linked with their superior microstructure. 12,28 In contrast, carbons pyrolyzed at lower temperatures performed worse, with lower onset potentials (as positive as 0.79 V vs RHE for C-500) and lower current densities.…”

“…27 Lee et al used electrospun tree-bark-shaped N-doped carbons to oxidize hydrazine with an onset of 0.51 V vs RHE at pH 14. 28 Despite these significant advances, the range of hydrazine oxidation electrocatalysts in the alkaline range is still limited. Moreover, control of catalyst nanostructure is challenging, as the precision of the synthesis is often at odds with its price and scalability.…”