Spray-Flame Synthesis of LaFe_xCo_1–xO₃ (x = 0.2, 0.3) Perovskite Nanoparticles for Oxygen Evolution Reaction in Water Splitting: Effect of Precursor Chemistry (Acetates and Nitrates)

Abstract

The product properties of mixed oxide nanoparticles generated via spray-flame synthesis depend on an intricate interplay of solvent and precursor chemistries in the processed solution. The effect of two different sets of metal precursors, acetates and nitrates, dissolved in a mixture of ethanol (35 Vol.%) and 2-ethylhexanoic acid (2-EHA, 65 Vol.%) was investigated for the synthesis of LaFe x Co 1−x O 3 (x = 0.2, 0.3) perovskites. Regardless of the set of precursors, similar particle-size distributions (d p = 8− 11 nm) were obtained and a few particles with sizes above 20 nm were identified with transmission electron microscopy (TEM) measurements. Using acetates as precursors, inhomogeneous La, Fe, and Co elemental distributions were obtained for all particle sizes according to energy dispersive X-ray (EDX) mappings, connected to the formation of multiple secondary phases such as oxygen-deficient La 3 (Fe x Co 1−x ) 3 O 8 brownmillerite or La 4 (Fe x Co 1−x ) 3 O 10 Ruddlesden−Popper (RP) structures besides the main trigonal perovskite phase. For samples synthesized from nitrates, inhomogeneous elemental distributions were observed for large particles only where La and Fe enrichment occurred in combination with the formation of a secondary La 2 (Fe x Co 1−x )O 4 RP phase. Such variations can be attributed to reactions in the solution prior to injection in the flame as well as precursor-dependent variations in in-flame reactions. Therefore, the precursor solutions were analyzed by temperature-dependent attenuated total reflection Fouriertransform infrared (ATR-FTIR) measurements. The acetate-based precursor solutions indicated the partial conversion of, mainly La and Fe, acetates to metal 2-ethylhexanoates. In the nitrate-based solutions, esterification of ethanol and 2-EHA played the most important role. The synthesized nanoparticle samples were characterized by BET (Brunauer, Emmett, Teller), FTIR, Mossbauer, and X-ray photoelectron spectroscopy (XPS). All samples were tested as oxygen evolution reaction (OER) catalysts, and similar electrocatalytic activities were recorded when evaluating the potential required to reach 10 mA/cm 2 current density (∼1.61 V vs reversible hydrogen electrode (RHE)).

Combustion in a Sustainable World: From Molecules to Processes

“…Flame synthesis offers possible routes for forming a wide variety of materials of utility in the energy transition. Angel et al explored the effect of different precursors on the spray-flame synthesis of LaFe x Co 1– x O 3 perovskite nanoparticles with characterizations via transmission electron microscopy, energy dispersive X-ray mappings, Fourier-transform infrared, Brunauer, Emmett, Teller, Mössbauer, and X-ray photoelectron spectroscopies . The samples obtained were also tested for their effectiveness as catalysts for the oxygen evolution reaction in water splitting .…”

“…Angel et al explored the effect of different precursors on the spray-flame synthesis of LaFe x Co 1−x O 3 perovskite nanoparticles with characterizations via transmission electron microscopy, energy dispersive X-ray mappings, Fourier-transform infrared, Brunauer, Emmett, Teller, Mossbauer, and X-ray photoelectron spectroscopies. 48 The samples obtained were also tested for their effectiveness as catalysts for the oxygen evolution reaction in water splitting. 48 These and other thermochemical conversion processes can benefit from decades of combustion research to improve their efficiency, selectivity, and emission signature.…”

“…48 The samples obtained were also tested for their effectiveness as catalysts for the oxygen evolution reaction in water splitting. 48 These and other thermochemical conversion processes can benefit from decades of combustion research to improve their efficiency, selectivity, and emission signature.…”

Forschungstransfer: Elektrochemische CO2‐Reduktion

“…Tausende Quadratkilometer Elektroden lassen sich nur im Schulterschluss zwischen den Natur-und Ingenieurwissenschaften realisieren, etwa durch die Entwicklung skalierbarer Syntheseverfahren sowie kontinuierlicher und automatisierter Sprühbeschichtungs-und Rolle-zu-Rolle-Prozesse. 24,25) Da es sich bei Elektrokatalysatoren häufig um Nanomaterialien handelt, sind funktionale Partikel im Sub-µm-Bereich herzustellen und zu handhaben. Dazu gehört die für die Beschichtung und Trocknung nötige Kolloidverfahrenstechnik, die gleichzeitig angegangen werden muss.…”

Sustainable Synthesis Strategies: A Comparative Life Cycle Perspective on LaFeO3 Nanoparticles

“…In addition, vapor phase methods of LFO bulk synthesis were reported that utilize spray−flame pyrolysis. 14 The sonication methods are promising alternatives to conventional methods due to its decreased time and energy requirements. 15 However, the utilization of complex and energy-intensive reagents in mainstream synthesis methods have influenced researchers in the direction of "green synthesis".…”