Structure, Activity, and Faradaic Efficiency of Nitrogen‐Doped Porous Carbon Catalysts for Direct Electrochemical Hydrogen Peroxide Production

Abstract

Carbon materials doped with nitrogen are active catalysts for the electrochemical two-electron oxygen reduction reaction (ORR) to hydrogen peroxide. Insights into the individual role of the various chemical nitrogen functionalities in the H O production, however, have remained scarce. Here, we explore a catalytically very active family of nitrogen-doped porous carbon materials, prepared by direct pyrolysis of ordered mesoporous carbon (CMK-3) with polyethylenimine (PEI). Voltammetric rotating ring-disk analysis in combination with chronoamperometric bulk electrolysis measurements in electrolysis cells demonstrate a pronounced effect of the applied potentials, current densities, and electrolyte pH on the H O selectivity and absolute production rates. H O selectivity up to 95.3 % was achieved in acidic environment, whereas the largest H O production rate of 570.1 mmol g h was observed in neutral solution. X-ray photoemission spectroscopy (XPS) analysis suggests a key mechanistic role of pyridinic-N in the catalytic process in acid, whereas graphitic-N groups appear to be catalytically active moieties in neutral and alkaline conditions. Our results contribute to the understanding and aid the rational design of efficient carbon-based H O production catalysts.

Enhancing the Selectivity between Oxygen and Chlorine towards Chlorine during the Anodic Chlorine Evolution Reaction on a Dimensionally Stable Anode

“…It should be pointed out that the detected changes in O 2 formation are extremely small resulting in a substantial impact of outliers, thus inducing larger error bars that were observed during all measurements ( Figure 2). RRDE voltammetry is well established in electrocatalysis to detect reaction (by)products [18,19,25] or to determine the faradaic efficiency of electrode reactions. [19,20] Since the feasibility of RRDE voltammetry for determination of the selectivity between O 2 and Cl 2 evolution was previously demonstrated for solutions at moderate ion concentrations [10] , we conducted RRDE measurements in order to validate the aforementioned trends.…”

“…RRDE voltammetry is well established in electrocatalysis to detect reaction (by)products [18,19,25] or to determine the faradaic efficiency of electrode reactions. [19,20] Since the feasibility of RRDE voltammetry for determination of the selectivity between O 2 and Cl 2 evolution was previously demonstrated for solutions at moderate ion concentrations [10] , we conducted RRDE measurements in order to validate the aforementioned trends. However, the high viscosity due to the high salt concentrations revealed RRDE to be an inappropriate technique (for further discussion of the RRDE experiments see supporting information, especially Figure S1, S2, S4).…”

Tailoring the Electrochemical Production of H2O2: Strategies for the Rational Design of High‐Performance Electrocatalysts

“…Nitrogen functionalization on porous carbon has been at the center of numerous researches as a potential high‐performance catalyst for H 2 O 2 production, with enhancements in surface area, conductivity, and catalytic performance. The current strategies on nitrogen functionalization include heat treatment in the presence of carbon and nitrogen sources, CVD, electrochemical doping, and nanocasting . For nitrogen functionalization, the higher electronegativity of the nitrogen atom within the carbon framework breaks the integrity of the π conjugate system and induces a charge redistribution,4b changing the adsorption properties of the intermediates on the carbon materials.…”

Effect of Experimental Operations on the Limiting Current Density of Oxygen Reduction Reaction Evaluated by Rotating‐Disk Electrode

“…The steady‐state limiting current density I lim , which indicates the maximum diffusion current in the ORR, is easily influenced by experimental conditions. The theoretical limiting current density I lim can be calculated by the following equation: , where ω is the rotating speed (rad ⋅ s −1 ), υ is the kinematic viscosity of the electrolyte (m 2 ⋅ s −1 ), C is the bulk concentration of O 2 (mol L −1 ), D is the diffusion coefficient (m 2 ⋅ s −1 ) of the electroactive species, F is the Faraday constant (96485.34 C mol −1 ), and n is the total number of electrons transferred during the electrochemical reaction . The limiting current density I lim is independent on the kinetics of the reaction.…”

“…where ω is the rotating speed (rad · s À 1 ), υ is the kinematic viscosity of the electrolyte (m 2 · s À 1 ), C is the bulk concentration of O 2 (mol L À 1 ), D is the diffusion coefficient (m 2 · s À 1 ) of the electroactive species, F is the Faraday constant (96485.34 C mol À 1 ), and n is the total number of electrons transferred during the electrochemical reaction. [6,[14][15][16][17] The limiting current density I lim is independent on the kinetics of the reaction. For a 4e ORR, I lim should be a fixed value in a particular concentration solution at 1600 rpm on a 5 mm working electrode, such as 5.277 mA cm À 2 for 0.5 M H 2 SO 4 , 6.332 mA cm À 2 for 0.1 M HClO 4 , and 5.968 mA cm À 2 for 0.1 M KOH (The parameters were listed in support information).…”