Plasma‐Triggered Synergy of Exfoliation, Phase Transformation, and Surface Engineering in Cobalt Diselenide for Enhanced Water Oxidation

Recent Advances and Future Perspectives of Metal-Based Electrocatalysts for Overall Electrochemical Water Splitting

Recently, the growing demand for a renewable and sustainable fuel alternative is contingent on fuel cell technologies. Even though it is regarded as an environmentally sustainable method of generating fuel for immediate concerns, it must be enhanced to make it extraordinarily affordable, and environmentally sustainable. Hydrogen (H₂ ) synthesis by electrochemical water splitting (ECWS) is considered one of the foremost potential prospective methods for renewable energy output and H₂ society implementation. Existing massive H₂ output is mostly reliant on the steaming reformation of carbon fuels that yield CO₂ together with H₂ and is a finite resource. ECWS is a viable, efficient, and contamination-free method for H₂ evolution. Consequently, developing reliable and cost-effective technology for ECWS was a top priority for scientists around the globe. Utilizing renewable technologies to decrease total fuel utilization is crucial for H₂ evolution. Capturing and transforming the fuel from the ambient through various renewable solutions for water splitting (WS) could effectively reduce the need for additional electricity. ECWS is among the foremost potential prospective methods for renewable energy output and the achievement of a H₂ -based economy. For the overall water splitting (OWS), several transition-metal-based polyfunctional metal catalysts for both cathode and anode have been synthesized. Furthermore, the essential to the widespread adoption of such technology is the development of reduced-price, super functional electrocatalysts to substitute those, depending on metals. Many metal-premised electrocatalysts for both the anode and cathode have been designed for the WS process. The attributes of H₂ and oxygen (O₂ ) dynamics interactions on the electrodes of water electrolysis cells and the fundamental techniques for evaluating the achievement of electrocatalysts are outlined in this paper. Special emphasis is paid to their fabrication, electrocatalytic performance, durability, and measures for enhancing their efficiency. In addition, prospective ideas on metal-based WS electrocatalysts based on existing problems are presented. It is anticipated that this review will offer a straight direction toward the engineering and construction of novel polyfunctional electrocatalysts encompassing superior efficiency in a suitable WS technique.

Crystal facet and phase engineering for advanced water splitting

This review covers the principles and recent advances in facet and phase engineering of catalysts for photocatalytic, photoelectrochemical, and electrochemical water splitting. It suggests the basis of catalyst design for advanced water splitting.

Defect-Rich High-Entropy Oxide Nanosheets for Efficient 5-Hydroxymethylfurfural Electrooxidation

High-entropy oxides (HEOs), a new concept of entropy stabilization, exhibit unique structures and fascinating properties, and are thus important class of materials with significant technological potential. However, the conventional high-temperature synthesis techniques tend to afford micron-scale HEOs with low surface area, and the catalytic activity of available HEOs is still far from satisfactory because of their limited exposed active sites and poor intrinsic activity. Here we report a low-temperature plasma strategy for preparing defect-rich HEOs nanosheets with high surface area, and for the first time employ them for 5-hydroxymethylfurfural (HMF) electrooxidation. Owing to the nanosheets structure, abundant oxygen vacancies, and high surface area, the quinary (FeCrCoNiCu)₃ O₄ nanosheets deliver improved activity for HMF oxidation with lower onset potential and faster kinetics, outperforming that of HEOs prepared by high-temperature method. Our method opens new opportunities for synthesizing nanostructured HEOs with great potential applications.

Nitrogen-Doped Cobalt Diselenide with Cubic Phase Maintained for Enhanced Alkaline Hydrogen Evolution

The introduction of heteroatoms is one of the most important ways to modulate the intrinsic electronic structure of electrocatalysts to improve their catalytic activity. However, for transition metal chalcogenides with highly symmetric crystal structure (HS-TMC), the introduction of heteroatoms, especially those with large atomic radius, often induces large lattice distortion and vacancy defects, which may lead to structural phase transition of doped materials or structural phase reconstruction during the catalytic reaction. Such unpredictable situations will make it difficult to explore the connection between the intrinsic electronic structure of doped catalysts and catalytic activity. Herein, taking thermodynamically stable cubic CoSe₂ phase as an example, we demonstrate that nitrogen incorporation can effectively regulate the intrinsic electronic structure of HS-TMC with structural phase stability and thus promote its electrocatalytic activity for the hydrogen evolution activity (HER). In contrast, the introduction of phosphorus can lead to structural phase transition from cubic CoSe₂ to orthorhombic phase, and the structural phase of phosphorus-doped CoSe₂ is unstable for HER.

Grain boundary engineering of Co3O4 nanomeshes for efficient electrochemical oxygen evolution

The development of high-efficiency and stable electrocatalysts is significant for energy conversion and storage. The oxygen evolution reaction (OER), a pivotal half reaction, is seriously limited in its practical applications due to its sluggish kinetics and thus an excellent electrocatalyst for OER is urgently required. In this paper, we design a novel Co₃O₄ nanomesh (Co₃O₄ NMs) with high density grain boundaries (GBs), which functions as a highly efficient and steady OER electrocatalyst. The optimal Co₃O₄ NMs-500 can achieve a low overpotential of 295 mV at a current density of 10 mA cm^-2, and a small Tafel slope of 31 mV dec^-1, which exceeds the commercial Ir/C, as well as the majority of other catalysts reported in the literature. The Co₃O₄ NMs-500 also exhibit promising durability, with a negligible decline in activity after 18 h of operation. Detailed studies indicate that the presence of GBs leads to more exposed active sites and the enhanced adsorption of intermediate species on Co₃O₄ NMs-500, thereby improving the OER's catalytic activity. This work not only relates to the activity-GBs relationship, but also opens up a unique perspective for the design of the next generation of electrocatalysts.

Amorphization activated ruthenium-tellurium nanorods for efficient water splitting

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 RuO_xH_y 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.

Elctrochemical water splitting is of vital significance for energy conversion and storage. Here the authors show an electrocatalyst based on amorphous ruthenium-tellurium porous nanorods which exhibit significantly improved OER performance than its crystalline counterparts

A Co-Doped Nanorod-like RuO2 Electrocatalyst with Abundant Oxygen Vacancies for Acidic Water Oxidation

Active and highly stable electrocatalysts for oxygen evolution reaction (OER) in acidic media are currently in high demand as a cleaner alternative to the combustion of fossil fuels. Herein, we report a Co-doped nanorod-like RuO₂ electrocatalyst with an abundance of oxygen vacancies achieved through the facile, one-step annealing of a Ru-exchanged ZIF-67 derivative. The compound exhibits ultra-high OER performance in acidic media, with a low overpotential of 169 mV at 10 mA cm⁻² while maintaining excellent activity, even when exposed to a 50-h galvanostatic stability test at a constant current of 10 mA cm⁻². The dramatic enhancement in OER performance is mainly attributed to the abundance of oxygen vacancies and modulated electronic structure of the Co-doped RuO₂ that rely on a vacancy-related lattice oxygen oxidation mechanism (LOM) rather than adsorbate evolution reaction mechanism (AEM), as revealed and supported by experimental characterizations as well as density functional theory (DFT) calculations.

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A Co-doped RuO₂ electrocatalyst with an abundance of oxygen vacancies was synthesized

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The compound exhibits ultra-high OER performance in acidic media

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The oxygen vacancies contribute to the high OER performance

Defective NiFe2 O4 Nanoparticles for Efficient Urea Electro-oxidation

Urea is an important organic pollutants in sewage and needs to be removed for environmental protection. Here, we report defective NiFe₂ O₄ (NFO) nanoparticles with excellent performance for urea electro-oxidation. The results show that defects can be effectively implanted at the surface of NFO nanoparticles by a facile and versatile lithium reduction method without affecting its main crystal structure and grain size. The defective NFO-5Li nanoparticles displayed a significantly improved urea electro-oxidation performance compared with NFO-Pristine nanoparticles. Particularly, the NFO-Pristine and NFO-5Li show a potential of 1.398 and 1.361 V at the current density of 10 mA cm^-2 and Tafel slope of 37.3 and 31.4 mV dec^-1 , respectively. In addition, the NFO-5Li nanoparticles also revealed outstanding electrocatalytic stability. The superior performance can be attributed to the designed tunable surface defect engineering. Furthermore, the defect engineering strategy as well as the defective NFO nanoparticles hold great potential for applications in other materials and areas.