Two-electron oxygen reduction reaction (2e-ORR) provides an environmentally friendly direction for the on-site production of hydrogen peroxide (H₂O₂). Central to this technology is the exploitation of efficient, economical, and safe 2e-ORR electrocatalysts. This overview starts with the fundamental chemistry of ORR to highlight the decisive role of adsorbing intermediates on the reaction pathway and activity, followed by a comprehensive survey of the tuning strategies to favor 2e-ORR on traditional precious metals. The latest achievements in designing efficient and selective precious-metal-based single-atom catalysts (SACs) and metal-nitrogen-carbon (M-N_x/C) catalysts, from the aspects of material synthesis, theoretical calculations, and mass transport promotion, are systematically summarized. Brief introductions on the evaluation metrics for 2e-ORR catalysts and the primary reactor designs for cathodic H₂O₂ synthesis are also included. We conclude this review with an outlook on the challenges and direction of efforts to advance electrocatalytic 2e-ORR into realistic H₂O₂ production.

The layered metal oxides are reviewed as the hopeful cathode materials for high-performance sodium-ion batteries (SIBs) due to their large theoretical capacity, favorable two-dimensional (2D) ion diffusion channel, and simple manipuility. However, their cycling stability, rate capability, and thermal stability are still significantly concerned and highlighted before further practical application. The chemical, mechanical and electrochemical stability of the cathode–electrolyte interfaces upon cycling is of great significance. Herein, the unique structural and electrochemical properties of the layered oxide cathode materials for SIB are reviewed. The mechanism of bulk/surface degradation induced by oxygen evolution, phase transition, microcrack, and electrolyte decomposition is thoroughly understood. Furthermore, the interfacial engineering to construct stable interface through various effective methods is fully discussed. The future outlook and challenges for interfacial engineering in this filed are also summarized. This review should shed light on the rational design and construct of robust interface for applications of superior layered oxide cathodes in SIB and may suggest future research directions.

Deep eutectic solvents (DESs) have been reported as a type of solvent for the controllable synthesis of metal nanostructures. Interestingly, flower-like palladium (Pd) nanoparticles composed of staggered nanosheets and nanospheres are spontaneously transformed into three-dimensional (3D) network nanostructures in choline chloride-urea DESs using ascorbic acid as a reducing agent. Systematic studies have been carried out to explore the formation mechanism, in which DESs itself acts as a solvent and soft template for the formation of 3D flower-like network nanostructures (FNNs). The amounts of hexadecyl trimethyl ammonium bromide and sodium hydroxide also play a crucial role in the anisotropic growth and generation of Pd-FNNs. The low electrocatalytic performance of Pd is one of the major challenges hindering the commercial application of fuel cells. Whereas, the 3D Pd-FNNs with lower surface energy and abundant grain boundaries exhibited the enhanced electrocatalytic activity and stability toward formic acid oxidation, by which the mass activity and specific activity were 2.7 and 1.4 times higher than those of commercial Pd black catalyst, respectively. Therefore, the current strategy provides a feasible route for the synthesis of unique Pd-based nanostructures.

Highly active, stable, and cut-price (photo-)electrocatalysts are desired to overwhelm high energy barriers for anodic oxygen evolution reaction processes. Herein, a heterostructure of cobalt-iron oxide/black phosphorus nanosheets is in-situ synthesized via a facile and novel three-electrode electrolysis method. Bulky black phosphorus is exfoliated into its nanosheets at the cathode while the CoFe oxide is derived directly from the metal wire anode during the electrolysis process. This heterostructure exhibits excellent electrocatalytic oxygen evolution reaction (OER) performance, and the overpotential at 10 mA·cm⁻² is 51 mV lower than that of the commercial RuO₂ catalyst. Its superior OER performance stems from the favorable adsorption behavior and an enlarged electrochemical active surface area of the catalyst. To reveal the origin of excellent OER performance from the point of adsorption strength of OH*, methanol oxidation reaction (MOR) test is applied under the identified OER operating conditions. Further introduction of light illumination enhances the OER activity of this heterostructure. The overpotential drops down to 280 mV, benefiting from pronounced photochemical response of black phosphorus nanosheets and iron oxide inside the heterostructure. This work develops a new electrochemical method to construct high performance and light-sensitive heterostructures from black phosphorus nanosheets for the OER.