The rational design and development of highly efficient oxygen evolution reaction (OER) electrocatalysts is vital for the application of renewable energy devices. Recently, the strategy of defect engineering draws much attention due to its positive effect on regulating the electronic structure, and thus, promoting the electrocatalytic performance of various materials. In this review, the main focus is on the cation vacancy defects of transition metal‐based electrocatalysts; the latest progress in cation vacancy defect engineering for the electrocatalytic OER is summarized. The different effects of cation vacancy defects on OER are well discussed together with the reaction mechanism, mainly including improving the conductivity, optimizing the adsorption of key intermediates, guiding the surface reconstruction to form active species, and enhancing the long‐term stability. Then, methods to construct cation vacancy defects on different electrocatalysts and the characterization of cation vacancies are systematically introduced. Finally, the remaining challenges and future prospects of cation vacancy defect engineering for promoting OER performance are further proposed.

Cation Defect Engineering of Transition Metal Electrocatalysts for Oxygen Evolution Reaction

Two-dimensional (2D) oxides have unique electrical, optical, magnetic, and catalytic properties, which are promising for a wide range of applications in different fields. However, it is difficult to fabricate most oxides as 2D materials unless they have a layered structure. Here, we present a facile strategy for the synthesis of ultrathin oxide nanosheets using a self-formed sacrificial template of carbon layers by taking advantage of the Maillard reaction and violent redox reaction between glucose and ammonium nitrate. To date, 36 large-area ultrathin oxides (with thickness ranging from ~1.5 to ~4 nm) have been fabricated using this method, including rare-earth oxides, transition metal oxides, III-main group oxides, II-main group oxides, complex perovskite oxides, and high-entropy oxides. In particular, the as-obtained perovskite oxides exhibit great electrocatalytic activity for oxygen evolution reaction in an alkaline solution. This facile, universal, and scalable strategy provides opportunities to study the properties and applications of atomically thin oxide nanomaterials.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9122325

Puffing ultrathin oxides with nonlayered structures

One core reaction involved in many electrochemical energy conversion systems is the oxygen evolution reaction (OER), which usually dominates the overall polarization loss due to its sluggish kinetics. Activating O2...

In Situ Surface Reconstruction of a Ni-based Perovskite Hydroxide Catalyst for an Efficient Oxygen Evolution Reaction

Hydrogen is considered a promising clean energy vector with the features of high energy capacity and zero-carbon emission. Water splitting is an environment-friendly and effective route for producing high-purity hydrogen, which contains two important half-cell reactions, namely, the anodic oxygen evolution reaction (OER) and the cathodic hydrogen evolution reaction (HER). At the heart of water splitting is high-performance electrocatalysts that efficiently improve the rate and selectivity of key chemical reactions. Recently, perovskite oxides have emerged as promising candidates for efficient water splitting electrocatalysts owing to their low cost, high electrochemical stability, and compositional and structural flexibility allowing for the achievement of high intrinsic electrocatalytic activity. In this review, we summarize the present research progress in the design, development, and application of perovskite oxides for electrocatalytic water splitting. The emphasis is on the innovative synthesis strategies and a deeper understanding of structure–activity relationships through a combination of systematic characterization and theoretical research. Finally, the main challenges and prospects for the further development of more efficient electrocatalysts based on perovskite oxides are proposed. It is expected to give guidance for the development of novel non-noble metal catalysts in electrochemical water splitting. 

/pdf/recent-advances-in-perovskite-catalysts-for-efficient-1bgxggxc.pdf

Recent Advances in Perovskite Catalysts for Efficient Overall Water Splitting

Electrocatalytic water splitting: Mechanism and electrocatalyst design

The design of high-performance and cost-effective electrocatalysts for water splitting is of prime importance for efficient and sustainable hydrogen production. In this work, a surface defect engineering method is developed for optimizing the electrocatalytic activity of perovskite oxides for water electrolysis. A typical ferrite-based perovskite oxide material La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) is used and regulated by selective acid etching. The optimal parameters for the surface treatment are identified. An efficient bifunctional perovskite oxide, denoted LSCF-30, is prepared by selectively corroding the A-site Sr element in the surface region, which is found to not only increase the exposure and decrease the coordination of B-site metals but also effectively modulate the electronic structure of these metals. The crystal lattice of the perovskite bulk is kept constant during surface engineering, which ensures the structural stability of the perovskite catalyst. The findings demonstrate an effective strategy of surface defect engineering in enhancing the performance of perovskite oxide electrocatalysts for water splitting.

Surface Defect Engineering on Perovskite Oxides as Efficient Bifunctional Electrocatalysts for Water Splitting.

Ammonia has been increasingly recognised as an effective hydrogen carrier to produce clean hydrogen free of COx emissions. This study reports the development of Ni‐based catalysts to efficiently crack ammonia into hydrogen and nitrogen. A series of catalysts with different Ni loadings supported on Na‐ZSM‐5 zeolite nanocrystals were prepared with the assistance of 1,10‐phenanthroline ligand. The coordination of Ni and the ligand led to the formation of uniform Ni nanoparticles with a mean size of ∼2.3 nm. These small Ni nanoparticles of the catalyst enabled a high activity in ammonia decomposition evaluated using a fixed‐bed reactor. Using the zeolite support in its pristine sodium form provided the catalyst with desired basicity. This promotes a strong metal‐support interaction, leading the catalyst to have high stability. The catalyst with 5 wt% Ni loading exhibited a high TOF of 3.51 s−1 with no performance degradation at 650 °C for 50 h.

Xiang Zhang

Papers

Surface Defect Engineering on Perovskite Oxides as Efficient Bifunctional Electrocatalysts for Water Splitting.

Na-ZSM-5 Zeolite Nanocrystals Supported Nickel Nanoparticles for Efficient Hydrogen Production from Ammonia Decomposition