Bio-inspired design of electrocatalysts for oxalate oxidation: a combined experimental and computational study of Mn–N–C catalysts

Abstract

We report a novel non-platinum group metal (non-PGM) catalyst derived from Mn and amino- antipyrine (MnAAPyr) that shows electrochemical activity towards the oxidation of oxalic acid comparable to Pt with an onset potential for oxalate oxidation measured to be 0.714 ± 0.002 V vs. SHE at pH = 4. The material has been synthesized using a templating Sacrificial Support Method with manganese nitrate and 4-aminoantipyrine as precursors. This catalyst is a nano-structured material in which Mn is atomically dispersed on a nitrogen-doped graphene matrix. XPS studies reveal high abundance of pyridinic, Mn-Nx, and pyrrolic nitrogen pointing towards the conclusion that pyridinic nitrogen atoms coordinated to manganese constitute the active centers. Thus, the main features of the MnAAPyr catalyst are it exhibits similarity to the active sites of naturally occurring enzymes that are capable of efficient and selective oxidation of oxalic acid. Density functional theory in plane wave formalism with Perdew, Burke and Ernzerhof functional was further used to study the stability and activity of different one-metal active centers that could exist in the catalyst. The results show that the stability of the Mn-Nx sites changes in the following order: MnN4 > MnN3C > MnN2C2 > MnN3. Based on the overpotentials of 0.64 V and 0.71 V vs. SHE, calculated using the free energy diagrams for the oxalate oxidation mechanism, we could conclude that the MnN3C and MnN2C2 sites are most probable Mn-Nx sites responsible for the reported catalytic activity of the new catalyst.

Air Breathing Cathodes for Microbial Fuel Cell using Mn-, Fe-, Co- and Ni-containing Platinum Group Metal-free Catalysts

“…Although the fitting of the Metal-N peak was done using the same Metal-N 4 coordination as an representative (Fig. S3), please note that different coordinations of metal are expected in the material [60], [61]. As it was previously shown on the example of iron and cobalt [60], sites with different coordination of metal are expected to result in relatively narrow distribution of N 1 s binding energies contributing to the same XPS region between pyridinic nitrogen peak at 398.3 eV and pyrrolic nitrogen peak at 401.2 eV.…”

Novel Hybrid Catalyst for the Oxidation of Organic Acids: Pd Nanoparticles Supported on Mn‐N‐3D‐Graphene Nanosheets

“…This is best illustrated in the case of the oxalic acid, where the hybrid Pd/Mn−N‐3D‐GNS catalyst is characterized with low onset potential due to the presence of Pd nanoparticles and higher currents than the ones measured for any of the components separately. This is most likely due to comparably high activity of both Mn−N‐C sites and metallic Pd for oxalate oxidation . In the case of the mesoxalic acid, the hybrid catalyst demonstrates only slightly lower currents than the intrinsically most active Mn−N‐3D‐GNS catalyst, however, the presence of Pd decreases the onset potential as compared to Mn−N‐3D‐GNS for almost 60 mV.…”

“…It was previously established that naturally occurring oxidizers of oxalic acid, such as enzymes oxalate oxidase and oxalate decarboxylase, contain Mn atoms in their reaction centers coordinated with the nitrogen atoms from three histidines . Our group has previously studied the effects of manganese‐nitrogen contained carbon matrix on the oxidation of oxalic acid, noting that the biomimetic approach leads to enhanced electrocatalytic performance towards the targeted organic acid . Unfortunately, there is little to no literature on the performance of the inorganic catalysts at neutral pH and the knowledge within this field can be greatly increased.…”

Evaluation of Pt Alloys as Electrocatalysts for Oxalic Acid Oxidation: A Combined Experimental and Computational Study

“…ZPE values were calculated using the vibrational frequencies obtained from the normal mode analysis, and entropy changes were obtained from standard molecular tables. 39 As it was described in the previous literature, 13,[40][41][42] the chemical potential for proton/electron pair can be related to that of the 1/2H 2 (g) by the use of the standard hydrogen electrode. The free energy change of the reaction can then be calculated as…”

“…5,[11][12][13][14][15] Unfortunately the materials, including organic, inorganic, and enzymatic catalysts that can electrochemically catalyze OA oxidation have high activation potentials greater than 0.6 V vs Ag/AgCl. [16][17][18] Metallic catalysts, such as gold, platinum, and palladium are usually explored.…”