Dual-Engineering Tailored Co3O4 Hollow Microspheres Assembled by Nanosheets for Boosting Oxygen Evolution Reaction

The development of efficient, low-cost electrocatalysts for the oxygen evolution reaction (OER) is crucial for advancing sustainable hydrogen production through water splitting. This study presents a dual-engineering strategy to enhance the OER performance of Co3O4 by synthesizing hollow microspheres assembled from nanosheets (HMNs) with abundant oxygen vacancies and highly active crystal facet exposure. Through a modified one-step hydrothermal process, Co3O4 HMNs with exposed (111) and (100) crystal facets were successfully fabricated, demonstrating superior OER activity compared to Co3O4 nanocubes (NCs) with only (100) facet exposure. The optimized Co3O4-5% HMNs exhibited a low overpotential of 330 mV at 10 mA cm-2 and a Tafel slope of 69 mV dec-1. The enhanced performance was attributed to the synergistic effects of crystal facet engineering and defect engineering, which optimized the Co-O bond energy, increased the number of active sites, and improved conductivity. The unique hollow structure further facilitated mass transport and prevented nanosheet stacking, exposing more edge sites for catalytic reactions. This work highlights the potential of geometric and electronic structure modulation in designing high-performance OER catalysts for sustainable energy applications.

Sight into a Rare-Earth-Based Catalyst with Spatial Confinement Effect from the Perspective of Electronic Structure

Rare-earth elements include 15 kinds of lanthanides as well as Sc and Y elements. Interestingly, the special electronic configuration of a lanthanide rare earth is [Xe]4fn5d0-16s2 (n = 0-14), which results in rare-earth materials' unique activity in such areas as thermal catalysis, electrocatalysis, photocatalysis, etc. It is worth noting that a class of materials with spatial confinement effects are playing an increasingly important role in the catalytic performance; especially, the construction of hollow multishelled structures (HoMSs) can further enhance the activity of rare-earth catalytic materials. In this review, we discuss in depth the important roles of the rare-earth 4f5d electronic structure. Subsequently, this review systematically summarizes the synthesis methods of rare-earth HoMSs and their research progress in the field of catalysis and specifically introduces the advanced characterization and analysis methods of rare-earth HoMSs. Finally, the research directions, application prospects, and challenges that need to be focused on in the future of rare-earth-based HoMSs are discussed and anticipated. We believe that this review will not only inspire more creativity in optimizing the local electronic structure and spatial confinement structure design of rare-earth-based catalysts but also provide valuable insights for designing other types of catalysts.

Effects of the Crystalline Properties of Hollow Ceria Nanostructures on a CuO-CeO2 catalyst in CO Oxidation

The development of an efficient and economic catalyst with high catalytic performance is always challenging. In this study, we report the synthesis of hollow CeO2 nanostructures and the crystallinity control of a CeO2 layer used as a support material for a CuO-CeO2 catalyst in CO oxidation. The hollow CeO2 nanostructures were synthesized using a simple hydrothermal method. The crystallinity of the hollow CeO2 shell layer was controlled through thermal treatment at various temperatures. The crystallinity of hollow CeO2 was enhanced by increasing the calcination temperature, but both porosity and surface area decreased, showing an opposite trend to that of crystallinity. The crystallinity of hollow CeO2 significantly influenced both the characteristics and the catalytic performance of the corresponding hollow CuO-CeO2 (H-Cu-CeO2) catalysts. The degree of oxygen vacancy significantly decreased with the calcination temperature. H-Cu-CeO2 (HT), which presented the lowest CeO2 crystallinity, not only had a high degree of oxygen vacancy but also showed well-dispersed CuO species, while H-Cu-CeO2 (800), with well-developed crystallinity, showed low CuO dispersion. The H-Cu-CeO2 (HT) catalyst exhibited significantly enhanced catalytic activity and stability. In this study, we systemically analyzed the characteristics and catalyst performance of hollow CeO2 samples and the corresponding hollow CuO-CeO2 catalysts.

Highly improved acetone oxidation performance over mesostructured CuxCe1−xO2 hollow nanospheres

Mesostructured CuxCe1−xO2 hollow nanospheres with porous shells and controllable Cu/Ce molar ratios exhibit highly improved catalytic acetone oxidation performance.

Recent Advances on the Rational Design of Non-Precious Metal Oxide Catalysts Exemplified by CuOx/CeO2 Binary System: Implications of Size, Shape and Electronic Effects on Intrinsic Reactivity and Metal-Support Interactions

Catalysis is an indispensable part of our society, massively involved in numerous energy and environmental applications. Although, noble metals (NMs)-based catalysts are routinely employed in catalysis, their limited resources and high cost hinder the widespread practical application. In this regard, the development of NMs-free metal oxides (MOs) with improved catalytic activity, selectivity and durability is currently one of the main research pillars in the area of heterogeneous catalysis. The present review, involving our recent efforts in the field, aims to provide the latest advances—mainly in the last 10 years—on the rational design of MOs, i.e., the general optimization framework followed to fine-tune non-precious metal oxide sites and their surrounding environment by means of appropriate synthetic and promotional/modification routes, exemplified by CuOx/CeO2 binary system. The fine-tuning of size, shape and electronic/chemical state (e.g., through advanced synthetic routes, special pretreatment protocols, alkali promotion, chemical/structural modification by reduced graphene oxide (rGO)) can exert a profound influence not only to the reactivity of metal sites in its own right, but also to metal-support interfacial activity, offering highly active and stable materials for real-life energy and environmental applications. The main implications of size-, shape- and electronic/chemical-adjustment on the catalytic performance of CuOx/CeO2 binary system during some of the most relevant applications in heterogeneous catalysis, such as CO oxidation, N2O decomposition, preferential oxidation of CO (CO-PROX), water gas shift reaction (WGSR), and CO2 hydrogenation to value-added products, are thoroughly discussed. It is clearly revealed that the rational design and tailoring of NMs-free metal oxides can lead to extremely active composites, with comparable or even superior reactivity than that of NMs-based catalysts. The obtained conclusions could provide rationales and design principles towards the development of cost-effective, highly active NMs-free MOs, paving also the way for the decrease of noble metals content in NMs-based catalysts.

Engineering CuOx–ZrO2–CeO2 nanocatalysts with abundant surface Cu species and oxygen vacancies toward high catalytic performance in CO oxidation and 4-nitrophenol reduction

CuO_x–ZrO₂–CeO₂ nanocrystalline catalysts were designed and synthesized by a solvent-free synthetic strategy, and exhibited excellent catalytic performance owing to the increased oxygen vacancies and better dispersed active metal species.

Investigation of the re-dispersion of matrix Cu species in CuxCe1−xO2 nanorod catalysts and its effect on the catalytic performance in CO-PROX

The CO-PROX catalytic performance is sensitive to the re-dispersion state of matrix copper species, which separate out as highly dispersed CuO_x under thermal treatment.

Triple-shelled CuO/CeO2 hollow nanospheres derived from metal–organic frameworks as highly efficient catalysts for CO oxidation

Through a metal–organic framework engaged strategy, triple-shelled CuO/CeO₂-8% hollow nanospheres are fabricated as superior nanocatalysts for CO oxidation with excellent catalytic activity and cyclic stability.