Understanding hydrazine oxidation electrocatalysis on undoped carbon

Abstract

Carbons are ubiquitous electrocatalytic supports for various energy-related transformations, especially in fuel cells. Doped carbons such as Fe–N–C materials are particularly active towards the oxidation of hydrazine, an alternative fuel...

Orthogonal Design of Fe−N4 Active Sites and Hierarchical Porosity in Hydrazine Oxidation Electrocatalysts

“…It does not arise from oxygen evolution since the solution pH does not change as much by the addition of hydrazine as to promote oxygen evolution by over 100 mV. The second peak arises from HzOR on the carbon support itself, as observed in Figure 7 but only appearing later due to wave overlap [60] …”

“…Still, the HzOR current densities on C600 to C900 were significantly higher than on Vulcan carbon. This demonstrates how the higher SSAs (2.5–3.7 times than Vulcan XC 72R, 235 m 2 ⋅ g), [59] and interconnected hierarchical porosity allow for better access to the carbon surface area, and thus to active sites, which are carbon edges and defects [60] …”

“…The second peak arises from HzOR on the carbon support itself, as observed in Figure 7 but only appearing later due to wave overlap. [60] Stability tests of corrole 1@C800 show gradual loss of activity: 29 % of the starting HzOR current density are lost after 50 cycles (Figure 9e). On other N 4 macrocycles, this could arise from demetallation, especially since loss of iron is promoted by nitrogen protonation due to the high local proton concentration generated by the HzOR.…”

“…This demonstrates how the higher SSAs (2.5-3.7 times than Vulcan XC 72R, 235 m 2 • g), [59] and interconnected hierarchical porosity allow for better access to the carbon surface area, and thus to active sites, which are carbon edges and defects. [60] When corroles 1-3 were tested without any porous carbon support (deposited directly on a glassy carbon disk electrodes), they exhibited excellent HzOR onset potentials. Corrole 1 showed the earliest E onset of 0.40 V vs. RHE and the highest current densities of the three (Figure 7b inset).…”

Lanthanoid coordination compounds as diverse self-templating agents towards hierarchically porous Fe–N–C electrocatalysts

“…The oxidation occurs in two waves, assigned to two active sites: first, a small wave on the nitrogen dopants; second, a larger wave on carbon defects. 85…”