Oxygen mobility in LaCoO3 perovskites

Ca substitution improves the catalytic activity of perovskite LaCoO3 toward toluene: comprehension of electronic structure alteration

For perovskite La1-xCaxCoO3 (Ca-x, x = 0-0.3), Ca-0.2 with the closest O p band center to the Fermi level, displays the best catalytic activity for toluene oxidation. The O p band center determines the reducibility and active oxygen content. This finding is beneficial for the design of highly active perovskite catalysts.

A hollow void catalyst of Co@C(Z-d)@void@CeO2 for enhancing the performance and stability of the Fischer-Tropsch synthesis

To enhance the catalyst performance of Fischer-Tropsch synthesis (FTS), removing the mass-transfer restriction in the catalysis synthesis is essential. Although the core-shell nanostructures can improve the activity and stability of the catalyst, they can restrict the reactants' diffusion towards the active sites and the transfer of the products from these sites in FTS. Creating an adequate porosity between the core and the outer shell of the catalyst structure can tackle this issue. In this work, the synthesized cobalt-based nano-catalyst is encapsulated with two shells and a middle porous shell. The first shell is a carbon shell at the core of the catalyst derived from ZIF-67, the second one is the outer shell of ceria, and the middle porous shell is formed by removing the sacrificial silica shell through the etching technique. The characterization and performance tests represent significant evidence of the etching treatment's impact on the FTS catalyst performance. Besides, molecular dynamics simulation is also utilized to clarify its effect. The FTS catalytic performance is enhanced more than 2 times with the etched catalyst versus the catalyst without it at 17.5 bar and a (H2/CO) ratio of 1.2. In addition, not only does the etched catalyst with high porosity play the role of a nanoreactor and intensify its catalytic performance, but it also has higher stability.

Role of La-based perovskite catalysts in environmental pollution remediation

Since the advent of the industrial revolution, there has been a constant need of efficient catalysts for abatement of industrial toxic pollutants. This phenomenon necessitated the development of eco-friendly, stable, and economically feasible catalytic materials like lanthanum-based perovskite-type oxides (PTOs) having well-defined crystal structure, excellent thermal, and structural stability, exceptional ionic conductivity, redox behavior, and high tunability. In this review, applicability of La-based PTOs in remediation of pollutants, including CO, NO x and VOCs was addressed. A framework for rationalizing reaction mechanism, substitution effect, preparation methods, support, and catalyst shape has been discussed. Furthermore, reactant conversion efficiencies of best PTOs have been compared with noble-metal catalysts for each application. The catalytic properties of the perovskites including electronic and structural properties have been extensively presented. We highlight that a robust understanding of electronic structure of PTOs will help develop perovskite catalysts for other environmental applications involving oxidation or redox reactions.

Design principles of noble metal-free electrocatalysts for hydrogen production in alkaline media: combining theory and experiment

Water electrolysis is a promising solution to convert renewable energy sources to hydrogen as a high-energy-density energy carrier. Although alkaline conditions extend the scope of electrocatalysts beyond precious metal-based materials to earth-abundant materials, the sluggish kinetics of cathodic and anodic reactions (hydrogen and oxygen evolution reactions, respectively) impede the development of practical electrocatalysts that do not use precious metals. This review discusses the rational design of efficient electrocatalysts by exploiting the understanding of alkaline hydrogen evolution reaction and oxygen evolution reaction mechanisms and of the electron structure-activity relationship, as achieved by combining experimental and computational approaches. The enhancement of water splitting not only deals with intrinsic catalytic activity but also includes the aspect of electrical conductivity and stability. Future perspectives to increase the synergy between theory and experiment are also proposed.

Growth of LaCoO3 crystals in molten salt: effects of synthesis conditions

Herein, several typical reaction media for the synthesis of LaCoO₃ (LCO) crystals were examined by X-ray absorption spectroscopy (XAS).

Catalytic oxidation of high-concentration CO over La0.9M0.1CoO3 (M = Ce, Sr) facilely promoted by glucose

Addition of glucose and introduction of Ce/Sr into LaCoO3 can create more oxygen vacancies and Co3+ active sites, facilitating the catalytic activity for CO oxidation.

Pulsed reactivity on LaCoO3-based perovskites: a comprehensive approach to elucidate the CO oxidation mechanism and the effect of dopants

In this contribution we focus on three lanthanum cobaltate perovskites: undoped, Sr-doped, and Cu-doped to investigate the effect of doping on catalytic activity through pulsed reactivity experiments.

Design, controlled synthesis, and properties of 2D CeO2/NiO heterostructure assemblies

Synthetic protocols to generate well-integrated frameworks of known composition are important for the rational design of advanced materials.

Water electrolysis on La(1-x)Sr(x)CoO(3-δ) perovskite electrocatalysts

Perovskite oxides are attractive candidates as catalysts for the electrolysis of water in alkaline energy storage and conversion systems. However, the rational design of active catalysts has been hampered by the lack of understanding of the mechanism of water electrolysis on perovskite surfaces. Key parameters that have been overlooked include the role of oxygen vacancies, B–O bond covalency, and redox activity of lattice oxygen species. Here we present a series of cobaltite perovskites where the covalency of the Co–O bond and the concentration of oxygen vacancies are controlled through Sr²⁺ substitution into La_1−xSr_xCoO_3−δ. We attempt to rationalize the high activities of La_1−xSr_xCoO_3−δ through the electronic structure and participation of lattice oxygen in the mechanism of water electrolysis as revealed through ab initio modelling. Using this approach, we report a material, SrCoO_2.7, with a high, room temperature-specific activity and mass activity towards alkaline water electrolysis.

Perovskite oxides are attractive candidates as catalysts for water electrolysis however their rational design is rare. Here, the authors report a series of cobaltite perovskites where the covalency of the Co-O bond and concentration of oxygen vacancies are controlled, and assess their catalytic performance.