Perovskite-Type Catalysts Prepared by Nanocasting: Effect of Metal Silicates on the Electrocatalytic Activity toward Oxygen Evolution and Reduction Reactions

Abstract

La 0.6 Sr 0.4 Fe 0.6 Mn 0.4 O 3−δ (LSFM) perovskite-type catalysts were prepared by a nanocasting route based on solution combustion synthesis, called the soft−hard templating (SHT) approach. Three silica hard templates with different textural properties were used to increase the specific surface area of the perovskites, and hence to improve their electrochemical activity for both oxygen evolution and reduction reactions. Careful structural and physicochemical characterization revealed that the materials are composites formed by crystalline LSFM perovskite and amorphous metal silicates, even after the etching procedure. Both the composites' specific surface area and the fraction of silicates are proportional to the silicas pore volume. Interestingly, the LSFM perovskite obtained by SHT has lower cell volumes than the parent oxide prepared without a silica template. The electrochemical characterization revealed the contrasting effects of the metal silicates on the performances of the electrodes. The LSFM-SHT-based electrodes have higher double-layer capacitance and higher current for oxygen evolution than those prepared with the parent LSFM. Furthermore, the LSFM-SHT-based electrodes show a preferential 4-electron pathway during the oxygen reduction reaction, if the amount of amorphous silicates is low (Si wt % < 3.5 wt %). However, the silicates also shift the onset potential of both oxygen evolution and reduction reactions to more positive and negative potential values, respectively, thus delaying the two reactions.

Water electrolysis: from textbook knowledge to the latest scientific strategies and industrial developments

“…628 Nano-scaled perovskites have been accessible by fine adjustment of synthesis conditions of wet chemical routes (sol-gel processes, [629][630][631][632] hydrothermal procedures [633][634][635][636][637][638][639][640][641] ) deposition approaches (chemical precipitation [642][643][644][645][646][647][648][649][650][651][652] physical-, [653][654][655][656][657] or chemical vapor deposition, 658-660 electrodeposition 617,661-663 ), electrospinning, [664][665][666][667] and template-based approaches. [668][669][670][671][672][673][674][675][676][677][678][679] Nanorods comprising SNCF are also accessible upon a facile electrospinning method (Fig.…”

“…628 Nano-scaled perovskites have been accessible by fine adjustment of synthesis conditions of wet chemical routes (sol–gel processes, 629–632 hydrothermal procedures 633–641 ) deposition approaches (chemical precipitation 642–652 physical-, 653–657 or chemical vapor deposition, 658–660 electrodeposition 617,661–663 ), electrospinning, 664–667 and template-based approaches. 668–679 Nanorods comprising SNCF are also accessible upon a facile electrospinning method (Fig. 32) and showed very good bifunctionality (HER + OER) with respect to water electrolysis (1.68 V cell voltage; j = 10 mA cm −2 ; 0.1 M KOH).…”

An Overview of Environmental Catalysis Mediated by Hydrogen Peroxide

“…In heterogeneous systems, the role of materials is determined not only by their chemical activity in a strict sense, but also by other physical-chemical characteristics, such as the materials' structures and morphologies. As the catalyst surface in the H 2 O 2 -mediated processes is involved in the adsorption and dissociation of oxygen/water molecules and oxygenated intermediates, a favorable surface charge, and the increase in the specific surface area and, thus, the number of active sites has been pursued as strategies to accelerate the reactions [80,81]. In this regard, Farhadian et al [82] highlighted the importance of the support within composites/functionalized materials in a review focused on mesoporous silica with high surface area and high pore volume, capable of loading and dispersing catalytically active iron species for heterogeneous Fenton oxidation reactions.…”

“…In general, when oxide materials are involved, catalytic activities have also been related to the degree and symmetry of the crystalline structure [80,167].…”