Polymetal-Chelated Fabrication of Bimetallic Nanophosphides as Electrocatalysts for Zinc-Air Batteries.

Bimetallic phosphides are considered as promising electrocatalysts for zinc-air batteries toward oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). To address the semi-conductor inherent low electronic conductivity and catalytic activity, a polymetal-chelated strategy is employed to in situ fabricate bimetallic nanophosphides within carbon matrix anchoring by chemical bonding. The employment of biomolecule polydopamine (PDA) efficiently anchors various transition metal ions due to its strong chelating capability via inherent functional groups. Furthermore, the chelation of multi-metal ion is proved to promote the formation of graphitic nitrogen. The bimetallic FexCoyP phosphides nanoparticles are intimately encapsulated in carbon matrix through in situ carbonization and phosphatization processes. When utilized in Zinc-air batteries, Fe0.20Co0.80P anchored within N, P co-doped sub-microsphere (Fe0.20Co0.80P /PNC) exhibit a maximum power density of 167 mW cm-2 and cycle life up to 270 cycles, with a round-trip voltage of 0.955 V. The mechanisms for catalytic activity passivation are ascribed to the etching of nitrogen and oxidation of phosphorus in carbon matrix, as well as the oxidation of the surface phosphide on the sub-microspheres. This study presents a promising candidate for advancing the further development of energy conversation catalysis.

Ambient Electrochemical Ammonia Synthesis: From Theoretical Guidance to Catalyst Design.

Ammonia, a vital component in the synthesis of fertilizers, plastics, and explosives, is traditionally produced via the energy-intensive and environmentally detrimental Haber-Bosch process. Given its considerable energy consumption and significant greenhouse gas emissions, there is a growing shift toward electrocatalytic ammonia synthesis as an eco-friendly alternative. However, developing efficient electrocatalysts capable of achieving high selectivity, Faraday efficiency, and yield under ambient conditions remains a significant challenge. This review delves into the decades-long research into electrocatalytic ammonia synthesis, highlighting the evolution of fundamental principles, theoretical descriptors, and reaction mechanisms. An in-depth analysis of the nitrogen reduction reaction (NRR) and nitrate reduction reaction (NitRR) is provided, with a focus on their electrocatalysts. Additionally, the theories behind electrocatalyst design for ammonia synthesis are examined, including the Gibbs free energy approach, Sabatier principle, d-band center theory, and orbital spin states. The review culminates in a comprehensive overview of the current challenges and prospective future directions in electrocatalyst development for NRR and NitRR, paving the way for more sustainable methods of ammonia production.

Formulating Multiphase Medium Anti-wetting States in an Air-Water-Oil System: Engineering Defects for Interface Chemical Evolutions.

Studies which regulate macroscopic wetting states on determined surfaces in multiphase media are of far-reaching significance but are still in the preliminary stage. Herein, inspired by the wettability subassembly of fish scales, Namib desert beetle shell, and lotus leaf upper side, interfaces in the air-water-oil system are programmed by defect engineering to tailor the anti-wetting evolution from double to triple liquid repellency states. By controlling the visible light irradiation and plasma treatment, surface oxygen vacancies on CuxO@TiO2 nanowires (NWs) can be healed or reconstructed. The original membrane or the membrane after plasma treatment possesses abundant surface oxygen vacancies, and the homogeneous hydrophilic membrane shows only double anti-wetting states in the water-oil system. By the unsaturated visible light irradiation time, the surface oxygen vacancy partially healed, the heterogeneous hydrophilic-hydrophobic components occupied the membrane surface, and the anti-wetting state finally changed from double to triple in the air-water-oil system. After the illumination time reaches saturation, it promotes the healing of all surface oxygen vacancies, and the membrane surface only contains uniform hydrophobic components and only maintains double anti-wetting state in the air-oil system. The mechanism of the triple anti-wetting state on a heterogeneous surface is expounded by establishing a wetting model. The wetting state and the adhesion state of the CuxO@TiO2 NW membrane show regional specificity by controlling the illumination time and region. The underwater oil droplets exhibit the "non-adhesive" and "adhesive" state in a region with unsaturated irradiation time or in an unirradiated region, respectively. Underwater oil droplet manipulation can be accomplished easily based on switchable wettability and adhesion. Current studies reveal that defect engineering can be extended to anti-wetting evolution in the air-water-oil system. Constructing an anti-wetting interface by heterogeneous components provides reference for designing the novel anti-wetting interface.

Optimizing the Void Size of Yolk-Shell Bi@Void@C Nanospheres for High-Power-Density Sodium-Ion Batteries.

Bismuth (Bi) has been demonstrated as a promising anode for Na-ion batteries (NIBs) because it has high gravimetry (386 mA h g-1) and volumetric capacity (3800 mA h cm-3). However, Bi suffers from large volume expansion during sodiation, leading to poor electrochemical performance. The construction of a nanostructure with sufficient void space to accommodate the volume change has been proven effective for achieving prolonged cycling stability. However the excessive void space will definitely decrease the volumetric energy density of the battery. Herein, we design optimized Bi@Void@C nanospheres (Bi@Void@C-2) with yolk-shell structure that exhibit the best cycling performance and enhanced volumetric energy density. The optimized void space not only could buffer the volume change of the Bi nanosphere but also could keep the high volumetric energy density of the battery. The Bi@Void@C-2 shows an excellent rate capacity of 173 mA h g-1 at ultrahigh current density of 100 A g-1 and long-cycle life (198 mA h g-1 at 20 A g-1 over 10 000 cycles). The origin of the superior performance is achieved through in-depth fundamental studies during battery operation using in situ X-ray diffraction (XRD) and in situ transmission electron microscope (TEM), complemented by theoretical calculations and ex situ TEM observation. Our rational design provides insights for anode materials with large volume variation, especially for conversion type and alloying type mechanism materials for batteries (i.e., Li-ion batteries, Na-ion batteries).