Alkaline water splitting is an attractive method for sustainable hydrogen production. Owing to the sluggish kinetics of alkaline water reduction and oxidation, it is crucial to understand the mechanism of the hydrogen evolution reaction/oxygen evolution reaction (HER/OER) and construct efficient electrocatalysts based on the structure–activity relationship. This review describes the fundamentals of the alkaline HER and OER, the design of noble and nonnoble HER electrocatalysts with low energy barriers, OER electrocatalysts based on binding energy, electronic structure, lattice oxygen, and surface reconstruction as well as the recent developments of bifunctional HER/OER electrocatalysts. Future perspectives towards alkaline water splitting electrocatalysts are also proposed.

Recent progress made in the mechanism comprehension and design of electrocatalysts for alkaline water splitting

Non‐Noble‐Metal‐Based Electrocatalysts toward the Oxygen Evolution Reaction

Pursuing active and durable water splitting electrocatalysts is of vital significance for solving the sluggish kinetics of the oxygen evolution reaction (OER) process in energy supply. Herein, theoretical calculations identify that the local distortion-strain effect in amorphous RuTe2 system abnormally sensitizes the Te-pπ coupling capability and enhances the electron-transfer of Ru-sites, in which the excellent inter-orbital p-d transfers determine strong electronic activities for boosting OER performance. Thus, a robust electrocatalyst based on amorphous RuTe2 porous nanorods (PNRs) is successfully fabricated. In the acidic water splitting, a-RuTe2 PNRs exhibit a superior performance, which only require a cell voltage of 1.52 V to reach a current density of 10 mA cm-2. Detailed investigations show that the high density of defects combine with oxygen atoms to form RuOxHy species, which are conducive to the OER. This work offers valuable insights for constructing robust electrocatalysts based on theoretical calculations guided by rational design and amorphous materials.

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Amorphization activated ruthenium-tellurium nanorods for efficient water splitting.

High-entropy perovskite fluorides (HEPFs) have great potential in electrocatalysis that has not been realized because of the limitation of a high-temperature synthetic route and the limited understanding of high-entropy materials. The use of HEPFs in effective oxygen evolution catalysis and a feasible synthesis route for HEPFs in a boiled solution by combining a hydrothermal method with mechanochemistry are first reported here. These HEPFs consisting of cost-effective elements dramatically gave excellent catalytic activity for the oxygen evolution reaction in an alkaline media.

High-Entropy Perovskite Fluorides: A New Platform for Oxygen Evolution Catalysis

As star material, perovskites have been widely used in the fields of optics, photovoltaics, electronics, magnetics, catalysis, sensing, etc. However, some inherent shortcomings, such as low efficiency (power conversion efficiency, external quantum efficiency, etc.) and poor stability (against water, oxygen, ultraviolet light, etc.), limit their practical applications. Downsizing the materials into nanostructures and incorporating rare earth (RE) ions are effective means to improve their properties and broaden their applications. This review will systematically summarize the key points in the design, synthesis, property improvements and application expansion of RE-containing (including both RE-based and RE-doped) halide and oxide perovskite nanomaterials (PNMs). The critical factors of incorporating RE elements into different perovskite structures and the rational design of functional materials will be discussed in detail. The advantages and disadvantages of different synthesis methods for PNMs will be reviewed. This paper will also summarize some practical experiences in selecting suitable RE elements and designing multi-functional materials according to the mechanisms and principles of REs promoting the properties of perovskites. At the end of this review, we will provide an outlook on the opportunities and challenges of RE-containing PNMs in various fields.

Rare-earth-containing perovskite nanomaterials: design, synthesis, properties and applications

Perovskite-based electrocatalysts are one of the most promising materials for oxygen evolution reaction (OER), but their activity and durability are still far from desirable. Herein, we demonstrate that the double perovskite LaFex Ni1-x O3 (LFNO) nanorods (NRs) can be adopted as highly active and stable OER electrocatalysts. The optimized LFNO-II NRs with Ni/Fe ratio of 8:2 achieve a low overpotential of 302 mV at 10 mA cm-2 and a small Tafel slope of 50 mV dec-1 , outperforming those of the commercial Ir/C. The LFNO-II NRs also show high OER stability with slight current decrease after 20 h. The enhanced activity is explained by the improved surface area, tailored electronic structure as well as strong hybridization between O and Ni.

Double Perovskite LaFe x Ni 1-x O 3 Nanorods Enable Efficient Oxygen Evolution Electrocatalysis

The selective hydrogenation of α,β-unsaturated aldehydes to value-added α,β-unsaturated alcohols is a significant process in chemical industry, while the design of a catalyst with desirable activity, selectivity, and stability is challenging. Herein, we construct a sesame cake-like Pt3Co nanoparticles (NPs)@Co(OH)2 nanosheets (NSs) architecture with strongly coupled Pt3Co–Co(OH)2 interaction for efficient selective hydrogenation catalysis. The intimate interaction accompanied by highly dispersive ultrasmall Pt3Co NPs largely promotes the selective hydrogenation of α,β-unsaturated aldehydes with cinnamaldehyde (CAL) conversion of 99.6% and selectivity of 91.3% to cinnamyl alcohol (COL) under mild conditions and high stability after 10 successive cycles. Significantly, the performance of Pt3Co NPs@Co(OH)2 can also be expanded to the selective hydrogenation of other α,β-unsaturated aldehydes. X-ray photoelectron spectroscopy (XPS) and attenuated total reflectance infrared (ATR-IR) spectra demonstrate that th...

A Strongly Coupled Ultrasmall Pt3Co Nanoparticle-Ultrathin Co(OH)2 Nanosheet Architecture Enhances Selective Hydrogenation of α,β-Unsaturated Aldehydes

Yueming Tan

Papers

Double Perovskite LaFe x Ni 1-x O 3 Nanorods Enable Efficient Oxygen Evolution Electrocatalysis

A Strongly Coupled Ultrasmall Pt3Co Nanoparticle-Ultrathin Co(OH)2 Nanosheet Architecture Enhances Selective Hydrogenation of α,β-Unsaturated Aldehydes