Enhanced Tribological Properties of Electrodeposited Fe-W Alloy Coatings through Carburization.

Carburization is a promising surface-hardening approach to maximize the tribological and mechanical properties of metals and alloys by making thin-layer surface carbides. The current study investigates the effect of carburizing on the electrodeposited Fe-W alloy coating. This process involeves the thermal decomposition of ethanol in an argon (Ar) atmosphere at varying temperatures. The amorphous electrodeposits of Fe-W alloy coating formed at optimized current density (500 A/cm2) are transformed to the uniform W-rich reinforced bimetallic carbide (Fe3W3C) layers at a carburizing temperature of 850 °C. The sample Fe-50WC (850 °C) shows enhanced hardness and highest wear resistance with a lowest specific wear rate (10-7 mm3/Nm) as compared to the as-electrodeposited Fe-W alloy and other Fe-W, Co-W, and hard chromium coatings reported in the literature. The present strategy can be applied to develop alternative, low cost, and environmentally friendly W-based composite coatings to replace the toxic chromium coatings.

Fused Aromatic Network Structures as a Platform for Efficient Electrocatalysis.

Fused aromatic network (FAN) structures are a category of ordered porous polymers that permit the specific fusion of building blocks into extended porous network structures with designed skeletons and pores. One significant feature of FANs is that their structures can be tailorable with fused aromatic rings without rotatable single-bond connectivity. As a result, the geometry and space orientation of the building blocks are easily incorporated to guide the topological expansion of the architectural periodicity. The variety of building units and fused linkages make FANs a promising materials platform for constitutional outline and functional design. The stably confined spaces of FAN architectures can be extended for the exchange of photons, ions, electrons, holes, and guest molecules, and exhibit customized chemical, electrochemical and optical properties. Herein, the main progress and advances in the field of 2D and 3D FANs and their utilization as a platform to develop efficient electrocatalysts for energy conversion and storage applications are summarized.

Encapsulating Iridium Nanoparticles Inside a 3D Cage-Like Organic Network as an Efficient and Durable Catalyst for the Hydrogen Evolution Reaction.

Developing efficient and durable electrocatalysts is key to optimizing the electrocatalytic hydrogen evolution reaction (HER), currently one of the cleanest and most sustainable routes for producing hydrogen. Here, a unique and efficient approach to fabricate and embed uniformly dispersed Ir nanoparticles in a 3D cage-like organic network (CON) structure is reported. These uniformly trapped Ir nanoparticles within the 3D CON (Ir@CON) effectively catalyze the HER process. The Ir@CON electrocatalyst exhibits high turnover frequencies of 0.66 and 0.20 H2 s-1 at 25 mV and small overpotentials of 13.6 and 13.5 mV while generating a current density of 10 mA cm-2 in 0.5 m H2 SO4 and 1.0 m KOH aqueous solutions, respectively, as compared to commercial Pt/C (18 and 23 mV) and Ir/C (20.7 and 28.3 mV). More importantly, the catalyst shows superior stability in both acidic and alkaline media. These results highlight a potentially powerful approach for the design and synthesis of efficient and durable electrocatalysts for HER.

Efficient Hydrogen Evolution Reaction Catalysis in Alkaline Media by All-in-One MoS2 with Multifunctional Active Sites.

MoS2 becomes an efficient and durable nonprecious-metal electrocatalyst for the hydrogen evolution reaction (HER) when it contains multifunctional active sites for water splitting derived from 1T-phase, defects, S vacancies, exposed Mo edges with expanded interlayer spacings. In contrast to previously reported MoS2 -based catalysts targeting only a single or few of these characteristics, the all-in-one MoS2 catalyst prepared herein features all of the above active site types. During synthesis, the intercalation of in situ generated NH3 molecules into MoS2 sheets affords ammoniated MoS2 (A-MoS2 ) that predominantly comprises 1T-MoS2 and exhibits an expanded interlayer spacing. The subsequent reduction of A-MoS2 results in the removal of intercalated NH3 and H2 S to form an all-in-one MoS2 with multifunctional active sites mentioned above (R-MoS2 ) that exhibits electrocatalytic HER performance in alkaline media superior to those of all previously reported MoS2 -based electrocatalysts. In particular, a hybrid MoS2 /nickel foam catalyst outperforms commercial Pt/C in the practically meaningful high-current region (>25 mA cm-2 ), demonstrating that R-MoS2 -based materials can potentially replace Pt catalysts in practical alkaline HER systems.