Highly Stable Doped Barium Niobate Based Electrocatalysts for Effective Electrochemical Coupling of Methane to Ethylene

Abstract

Methane conversion into value‐added products such as olefins and aromatics is gaining increased attention in the wake of new natural gas reserve discoveries. Electrochemical oxidative coupling of methane (E‐OCM) provides better product selectivity as the product distribution can be controlled by applied potential as well as the oxide ion flux. Here a new catalyst based on Mg and Fe codoped barium niobate perovskites is reported. The prepared perovskites show excellent chemical stability in CH4‐rich environments up to 925 °C while showing methane activation properties from 600 °C. E‐OCM measurements indicate an ethylene production rate of 277 µmol cm−2 h−1 with a faradaic efficiency of 20% at 1 V and durable operation for six continuous days. X‐ray photoelectron spectroscopic measurements indicate significant Nb valency reorganization that can be the reason for its chemical stability. Nevertheless, the surface area of the catalyst is significantly lower and requires improvements in synthesis methodologies to improve catalytic activity further. The exceptional chemical stability of this perovskite material under methane exposure at high temperatures has significant importance as this material can be used as a catalyst and/or support in a wide variety of applications relevant for efficient energy conversion and storage.

Chemical Stability of BaMg0.33Nb0.67-XFexO3-δ in High Temperature Methane Conversion Environments

“…Thus, here we explored the use of a perovskite material previously demonstrated to be stable for CO 2 gas sensing applications, BaMg 0.33 Nb 0.67-x Fe x O 3-δ (BMNF) (1). When using BMNF as an anode for E-OCM, we found that this material is both capable of converting methane into ethylene products (at cell voltages >0V versus air) and withstanding high temperature holds at temperatures up to 900 °C for over 100 hours without coking or structural collapse (2). Therefore, this article aims to explore how this class of perovskites at lower doping levels maintains stability in methane environments, via temperature programmed reaction (TPR) measurements, as well as further property modifications via doping or by decorating the parent barium magnesium niobate with Fe nanoparticles.…”

“…Figure 2a features BMN, BaMg 0.33 Nb 0.67 O 3-δ without any Fe, to test the reactivity of the perovskite. Previously, it was found that the conductivity of these BMNF materials was greatly enhanced by the addition of Fe (2). The BMN material has a conductivity <<1 mS/cm, making it effectively an insulator at these reaction conditions.…”

“…However, our previous electrochemical testing has shown BMNF25 to be stable and responsive to voltage after high temperature holds. (2) This may indicate that Fe sites on the surface of BMNF25 are not poisoned or formed into Fe nanoclusters, which would affect the activity of the partial oxidation catalyst.…”

Role of Dopants in Fine-Tuning the Electrical and Catalytic Properties of Barium Niobate Perovskites Towards High-Temperature Electrolyzer Application

“…We recently reported Mg and Fe codoped barium niobates for EOCM application where it showed good methane activation and chemical stability properties under these conditions (12). However, their electrical conductivity at 900 C was only about 17 mScm -1 that restricted the overall achievable current densities.…”

Recent Developments in Sensor Technologies for Enabling the Hydrogen Economy

“…[18][19][20] Hence, significant effort is also being undertaken to sense methane leaks efficiently or to convert it into higher hydrocarbons to reduce fugitive emissions and flaring. 21,22 The other carrier, ammonia can be harmful to human and animal health if inhaled at concentration levels of 50 parts per million (ppm) over an 8 h period according to the Occupational Safety and Health Administration (OSHA). 23 Key characteristics of all three gases are listed in Table I.…”