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Perovskite oxides are regarded as promising electrocatalysts for water splitting due to their cost‐effectiveness, high efficiency and durability in the oxygen evolution reaction (OER). Despite these advantages, a fundamental understanding of how critical structural parameters of perovskite electrocatalysts influence their activity and stability is lacking. Here, we investigate the impact of structural defects on OER performance for representative LaNiO3 perovskite electrocatalysts. Hydrogen reduction of 700 °C calcined LaNiO3 induces a high density of surface oxygen vacancies, and confers significantly enhanced OER activity and stability compared to unreduced LaNiO3; the former exhibit a low onset overpotential of 380 mV at 10 mA cm−2 and a small Tafel slope of 70.8 mV dec−1. Oxygen vacancy formation is accompanied by mixed Ni2+/Ni3+ valence states, which quantum‐chemical DFT calculations reveal modify the perovskite electronic structure. Further, it reveals that the formation of oxygen vacancies is thermodynamically more favourable on the surface than in the bulk; it increases the electronic conductivity of reduced LaNiO3 in accordance with the enhanced OER activity that is observed. [ABSTRACT FROM AUTHOR]

Oxide perovskites have emerged as an important class of materials with important applications in many technological areas, particularly thermocatalysis, electrocatalysis, photocatalysis, and energy storage. However, their implementation faces numerous challenges that are familiar to the chemist and materials scientist. The present work surveys the state-of-the-art by integrating these two viewpoints, focusing on the critical role that defect engineering plays in the design, fabrication, modification, and application of these materials. An extensive review of experimental and simulation studies of the synthesis and performance of oxide perovskites and devices containing these materials is coupled with exposition of the fundamental and applied aspects of defect equilibria. The aim of this approach is to elucidate how these issues can be integrated in order to shed light on the interpretation of the data and what trajectories are suggested by them. This critical examination has revealed a number of areas in which the review can provide a greater understanding. These include considerations of (1) the nature and formation of solid solutions, (2) site filling and stoichiometry, (3) the rationale for the design of defective oxide perovskites, and (4) the complex mechanisms of charge compensation and charge transfer. The review concludes with some proposed strategies to address the challenges in the future development of oxide perovskites and their applications. [ABSTRACT FROM AUTHOR]

This feature article summarizes the recent progress in porous perovskite oxides as advanced catalysts for both energy conversion applications and various heterogeneous reactions. Recently, research has been focused on specifically designing porous perovskite materials so that large surface areas can be harnessed and surface properties can be improved. Numerous potential applications of porous perovskites have been investigated, including heterogeneous catalysis and air battery applications that rely on interactions and/or reactions of other components with porous perovskites. The main objective of this article is to examine the progress of recent research studies on porous perovskite nanomaterials, including the preparation methods and their applications in catalysis and batteries. The wide variety of the related knowledge on porous mixed oxides can provide guidance for researchers with interests ranging from the design of functionalized materials to the field of heterogeneous catalysis and electrochemical applications. [ABSTRACT FROM AUTHOR]

BACKGROUND The effect of the B cation on the surface properties and catalytic activity in the dry reforming reaction over La0. 4M0. 6Al0. (M=noble metal) perovskite-type oxides with surface area 3.26-4.14 m2Ni0. 8O3 (M=noble metal) perovskite-type oxides with surface area 3.26-4.14 m2 g-1 and rhombohedral structure was studied. RESULTS Among LaAlxNi1- had the highest catalytic activity, but suffered a slow deactivation with time-on-stream ( TOS). It is observed that all samples presented similar activity at low reaction temperatures (500-600°C), while at higher temperatures (600-850°C) the prepared solid was more active and perovskite phase was transformed into NixO3 series, LaAl0. 2Ni0. 8O3 had the highest catalytic activity, but suffered a slow deactivation with time-on-stream ( TOS). It is observed that all samples presented similar activity at low reaction temperatures (500-600°C), while at higher temperatures (600-850°C) the prepared solid was more active and perovskite phase was transformed into Ni0 or La2O2CO3. It was found that among the noble metal samples, La0. 4Rh0. 6Al0. 2Ni0. 8O3 possessed the highest surface area and surface oxygen concentration and the best low-temperature reducibility. For the Rh catalyst the CH4 and CO2 conversions were 89.1 and 86.2%, which were the most resistant against coke deposition and showed very high stability without decrease in reforming and remained constant during the 3000 min TOS. The following order of activity was observed: La0. 4Rh0. 6Al0. 2Ni0. 8O3 > La0. 4Ru0. 6Al0. 2Ni0. 8O3 > LaAl0. 2Ni0. 8O3> La0. 4Ir0. 6Al0. 2Ni0. 8O3 ≥La0. 4Pt0. 6Al0. 2Ni0. 8O3 > La0. 4Pd0. 6Al0. 2Ni0. 8O3. CONCLUSIONS It is believed that the high surface area and surface oxygen concentration and good low-temperature reducibility were responsible for the good catalytic performance of the La0. 4Rh0. 6Al0. 2Ni0. 8O3 sample. © 2013 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Highlights: [•] LSCO synthesized via a novel and facile one-pot dextrose-assisted hydrothermal route. [•] High-surface-area nanowire LSCO is prepared by the DHR method. [•] Surface area, Oads content, and reducibility account for the good catalytic activity. [•] Catalytic activity is related to surface area, oxygen adspecies and reducibility. [•] l-Lysine/dextrose ratio can greatly influence on the morphology and pore structure. [ABSTRACT FROM AUTHOR]

Photocatalytic hydrogen (H2) production by water splitting provides an alternative to fossil fuels using clean and renewable energy, which gives important requirements about the efficiency of photocatalysts, co-catalysts, and sacrificial agents. To achieve higher H2 production efficiencies from water splitting, the study uses different metals such as yttrium (Y), praseodymium (Pr), magnesium (Mg), Indium (In), calcium (Ca), europium (Eu), and terbium (Tb) doped lanthanum iron oxide (LaFeO3) perovskites. They were synthesized using a co-precipitate method in a citric acid solution, which was loaded with the rhodium chromium oxide (RhCrOx) cocatalysts by an impregnation method along with a detailed investigation of photocatalytic hydrogen evolution performance. Photoluminescence (PL) and UV–Vis diffuse reflectance spectra (DRS) measured the rate of electron–hole recombination for RhCrOx/Pr-LaFeO3 photocatalysts, and X-ray powder diffraction (XRD), scanning electron microscope (SEM), high resolution transmission electron microscope (HRTEM), and X-ray photoelectron spectra (XPS) analyzed their characteristics. The experimental results obtained show that the samples with 0.5 wt.% RhCrOx loading and 0.1 M Pr-doped LaFeO3 calcined at a temperature of 700 °C (0.1Pr-LaFeO3-700) exhibited the highest photocatalytic H2 evolution rate of 127 µmol h−1 g−1, which is 34% higher photocatalytic H2 evolution performance than undoped LaFeO3 photocatalysts (94.8 μmol h−1 g−1). A measure of 20% of triethanolamine (TEOA) enabled a high hole capture capability and promoted 0.1-Pr-LaFeO3-700 to get the highest H2 evolution rate. [ABSTRACT FROM AUTHOR]

Nano‐sized perovskites were synthesized in a spray flame from nitrate precursors dissolved in ethanol and in ethanol/2‐ethylhexanoic acid (2‐EHA) mixtures. Experiments with ethanol led to a broad particle‐size distribution and to the formation of undesired phases such as La2CoO4, La2O3, and Co3O4. The addition of 2‐EHA can initiate micro explosions of the burning droplets and has been systematically investigated toward the formation of single‐phase, high‐surface‐area LaCoO3 and LaFeO3 with a narrow size distribution. To investigate the effect of 2‐EHA, temperature‐dependent changes of the chemical composition of the precursor solutions were analyzed with ATR‐FTIR between 23 and 70°C. In all cases, the formation of esters was identified while in the solutions containing iron, additional formation of carboxylates was observed. The synthesized materials were characterized by BET SSA, XRD, SAED and EDX‐TEM and their catalytic activity was analyzed, reaching 50% CO conversion at temperatures below 160 and 300°C for LaCoO3 and LaFeO3, respectively. [ABSTRACT FROM AUTHOR]

Tailoring the surface structure of Earth-abundant perovskite oxides can provide cost-effective, high-efficient, and durable electrocatalysts for oxygen evolution reaction (OER). However, the structural origin leading to high OER performance of perovskite is not fully understood. Here, we present a strategy of tuning the surface energy density of non-stoichiometric perovskite by creating surface defects in the 3D inverse opal LaCoO 3-x (3DIO-LaCoO 3-x) through a colloidal template strategy. The defective 3DIO-LaCoO 3-x , which has an enhanced surface energy density and a shift in the d-band centre of Co relative to the Fermi level, demonstrates significantly improved intrinsic OER activity, with a TOF (0.21 s−1) ten-folder larger than that of conventional LaCoO 3 nanoparticles (0.02 s−1). The defective surfaces of 3DIO-LaCoO 3-x are theoretically proven to alter the rate determining step of OER and significantly reduce the adsorption energies of the intermediate species, resulting in dramatically enhanced OER activity. Moreover, rich surface defects with high electrical conductivity can mitigate structural corrosion by fast transfer of charge through defective conductive channels, and thus enables long-term stability for the defective 3DIO-LaCoO 3-x. These results provide an effective approach for enhancing the intrinsic activity of perovskite for water oxidation towards understanding the surface structure engineering for perovskite-based materials. Image 1 • A surface defective 3D inverse opal LaCoO 3-x perovskite was synthesized. • Rich surface defects modified surface energy density and d-band centre of Co. • Intrinsic activity and stability against OER were significantly increased. • Defective sites reduced the energy barrier of the rate determining step of OER. [ABSTRACT FROM AUTHOR]