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

Abstract

Metal-free N-doped porous carbon has great potential as a catalyst for hydrazine oxidation in direct hydrazine fuel cells (DHFCs). However, previous studies have reported only half-cell characterization, and the effect of the pore size distribution has not been intensively investigated. Herein, we report the synthesis of highly active, metal-free N-doped carbon (NDC) by controlling the pore size distribution, and for the first time, the effect of the pore size distribution on the anode performance in a DHFC is investigated. As a result, tree-bark-shaped NDC with meso/macroporous (>10 nm) structures exhibit a remarkable power density of 127.5 mW cm in a DHFC.

A Multi‐Doped Electrocatalyst for Efficient Hydrazine Oxidation

“…Thed isordered/graphitic peak intensity ratio (I D /I G )decreases from 1.30 (NC) to 1.01 (Fe 2 MoC@NC), av alue sufficient for excellent electrocatalysis. [17,28] This onset potential is only 300-500 mV more positive than electrocatalysts based on precious metals (Pt, Pd, Au); or on metals whose surface quickly oxidizes during HzOR (Ni, Co);o ronu nsupported particles (Table S6). RHE for both Fe 2 MoC@NC and wash-Fe 2 MoC@NC (Figure 2a).…”

“…Moreover,e ven if several dopants are present, their separation in space prevents true cooperativity.For example,even in multi-doped particle/support HzOR catalysts, [7] only reactants located near the base of each particle base can interact with both particle and support surfaces,u nless the particles are very small. The catalyst operates at low overpotentials with high faradaic efficiency,a nd is stable for thousands of cycles.B yu sing carbon as as upport, [14][15][16][17] we could emulate other enzyme features such as nanometric active sites,h igh dispersion on arobust scaffold, and pathways for flow of reagents,products and charge to/from the catalytic sites. [13] Thec atalyst is composed of nanometric Fe 2 MoC supported on N-doped, porous,g raphitic carbon (Scheme 1).…”

A Multi‐Doped Electrocatalyst for Efficient Hydrazine Oxidation

“…The multi‐doped catalysts show excellent HzOR activity, with an onset as low as 0.28 V vs. RHE for both Fe 2 MoC@NC and wash‐Fe 2 MoC@NC (Figure a). This is the most negative onset potential reported so far for carbon‐based HzOR catalysts at pH 14 . This onset potential is only 300–500 mV more positive than electrocatalysts based on precious metals (Pt, Pd, Au); or on metals whose surface quickly oxidizes during HzOR (Ni, Co); or on unsupported particles (Table S6).…”

“…The catalyst operates at low overpotentials with high faradaic efficiency, and is stable for thousands of cycles. By using carbon as a support, we could emulate other enzyme features such as nanometric active sites, high dispersion on a robust scaffold, and pathways for flow of reagents, products and charge to/from the catalytic sites.…”

Strategies to Hierarchical Porosity in Carbon Nanofiber Webs for Electrochemical Applications

“…Other templates including Prussian blue analogues [24] and metal organic frameworks [25][26][27] have been used in conjunction with polymer precursors, conferring both porosity and heteroatom doping to CNFs obtained by electrospinning and carbonization. Sacrificial polymers or organic molecules such as polymethyl methacrylate (PMMA) [6,14,[28][29][30], polyvinylpyrrolidone (PVP) [31,32], poly(ethylene oxide) [33], Nafion ® [34], polysulfone [35], polystyrene [36], poly-L-lactic acid [37] and beta-cyclodextrin [38] can also be spun together with the main carbon precursor (any polymer forming conductive carbon with high yield during pyrolysis), allowing the formation of porous CNFs upon their removal by solvent or thermal treatment. Different kinds of templates can further be combined to produce hierarchical porosity, which is crucial for the transport of different species (ions, gases, liquids) in the electrodes of various electrochemical devices.…”