Abstract
The perovskite-type oxide Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF) is known as a highly active and stable oxygen evolution reaction (OER) electrocatalyst composited out of non-noble metals. The possibility of using the scalable flame spray synthesis (FSS) technique for the production of BSCF nanoparticles intensified the interest in this material for a future application in an alkaline water electrolyzer. A possible scale-up would require the optimization of the synthesis parameters to maximize the production rate. To further understand the influence of the synthesis parameters of the tunable FSS on the OER activity of BSCF, a systematic study was carried out by producing BSCF with different total metal concentrations (CTM), flow rates of the precursor solution (FRPS) and of the dispersion gas (FRDG). This study reveals that all three parameters have a direct impact on the OER activity of BSCF—measured in a rotating disc electrode (RDE) setup—due to the controllability of the initial Co and Fe oxidation state—indicated by X-ray absorption spectroscopy (XAS) measurements—and with that also of the oxygen vacancy concentration in the as-synthesized BSCF. This controllability enables the optimization of the OER activity of BSCF and emphasizes the importance of having Co in a lower initial oxidation state for reaching a high electrocatalytic performance.
Highlights
One of the biggest challenges of this century—the replacement of the 89% share of the world primary energy consumption based on non-renewable energy sources [1]—requests for efficient energy storage technologies to equilibrate the supply and demand of renewables
The three synthesis parameters do not have a significant influence on the crystallinity of Ba0.5 Sr0.5 Co0.8 Fe0.2 O3-δ (BSCF) but they have an impact on the secondary phases, especially the two flow rate parameters—flow rate of the precursor solution (FRPS) and flow rate of the dispersion gas (FRDG)
A systematic study was carried out to reveal the influence of the total metal concentration (CTM ) in the precursor solution, the flow rate of the precursor solution (FRPS ) and the flow rate of the dispersion gas (FRDG ) as flame spray synthesis (FSS) parameters on the oxygen evolution reaction (OER) activity of Ba0.5 Sr0.5 Co0.8 Fe0.2 O3-δ (BSCF)
Summary
One of the biggest challenges of this century—the replacement of the 89% share of the world primary energy consumption based on non-renewable energy sources [1]—requests for efficient energy storage technologies to equilibrate the supply and demand of renewables. Despite the tremendous research effort in recent decades, no golden path solution has been presented to date, indicating that a combination of technologies specialized for different time- and size scales are required for solving this challenge. Catalysts 2020, 10, 984 storage of renewable produced surplus electricity is the so-called “Hydrogen Economy” [2]. In such an economy, hydrogen (H2 ) acts as an energy vector [3] which is synthesized with renewable produced surplus electricity mainly via water electrolysis [4,5]. Improvements in electrocatalysts are required to minimize the overpotential of the OER and increase the overall efficiency, resulting in the low-cost production of H2
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