Dodecahedral W@WC Composite as Efficient Catalyst for Hydrogen Evolution and Nitrobenzene Reduction Reactions

Bio-Inspired Superhydrophilic Self-Assembled Coronavirus-Like Pt-WC/CNT for Hydrogen Evolution Reaction

This study presents a novel approach to enhance the catalytic activity of composite materials by promoting active surface exposure and improving hydrogen transfer performance. Through a self-assembly route involving tailored gas-solid and galvanic replacement reactions, Pt-WC/CNT catalysts with superhydrophilicity and coronavirus-like structure are synthesized. These unique structural features contribute to a remarkable enhancement in the electrocatalytic performance of the hydrogen evolution reaction (HER). Notably, the Pt-WC/CNT catalyst exhibits an outstanding intrinsic activity and efficient bubble transfer properties, leading to a high turnover frequency of 34.97 H2·s-1 at an overpotential of 100 mV. This value is 4.8 times higher than that achieved by commercial Pt/C catalysts (7.30 H2·s-1), establishing Pt-WC/CNT as one of the most active catalysts reported to date. Moreover, the combination of gas-solid and galvanic replacement reactions in the synthesis process offers a scalable route for the production of Pt-loading controllable composite catalysts, thus challenging the dominance of commercial Pt/C catalysts.

Mott-Schottky Effect in Core-Shell W@Wx C Heterostructure: Boosting Both Electronic/Ionic Kinetics for Lithium Storage

The dynamics rate of traditional metal carbides (TMCs) is relatively slow, severely limiting its fast-charging capacity for lithium-ion batteries (LIBs). Herein, the core-shell W@Wx C heterostructure is developed to form Mott-Schottky heterostructure, thereby simultaneously accelerating the electronic and ionic transport kinetics during the charging/discharging process. The W nanoparticles are partially reduced into Wx C to form a particular core-shell structure with abundant heterogeneous interfaces. Benefiting from the Mott-Schottky effect, the electrons at the metal/semiconductor heterointerface can migrate spontaneously to realize an equal work function on both sides. In addition, the independent nanoparticle as well as the unique core-shell structure facilitate the ionic diffusion kinetics. As expected, the W@Wx C electrode exhibits excellent electrochemical stability for LIBs, whose capacity can be maintained at 173.8 mA h g-1 after 1600 cycles at a high current density of 5 A g-1 . When assembled into a full cell, it can achieve an energy density of 360.2 Wh kg-1 . This work presents a new avenue to promote the electronic and ionic kinetics for LIBs anodes by constructing the unique Mott-Schottky heterostructure.

Liquid-Metal-Assisted Synthesis of Single-Crystalline TiC Nanocubes with Exposed {100} Facets for Enhanced Electrocatalytic Activity in the Hydrogen Evolution Reaction

Although TiC nanostructures show promise as non-noble-metal-based electrocatalysts, improved synthesis methods are required. Herein, single-crystalline TiC nanocubes with exposed {100} facets are grown by combusting TiO₂  + kMg + C reactive mixtures (k = 4-6.5 mol) in argon. During the synthesis, the temperature increases to 1200-1550 °C and excess Mg (2-4.5 mol) forms a liquid pool. The obtained TiC nanocubes have edge lengths of 50-300 nm and surface areas of 12.2-30.05 m² g^-1 . Insights into the TiC nanocube formation mechanism are obtained using density functional theory modeling of the surface energies of TiC nanocrystals and shape visualization using the Wulff construction method. During TiC nucleation and growth within the Mg melt, liquid Mg likely acts as a capping agent for {111} facets, thus promoting the formation of {100} facets. The TiC nanocubes show high electrocatalytic activity for the hydrogen evolution reaction, with a lower overpotential (0.298 V at 10 mA cm^-2 ) than other TiC nanostructures (0.400-0.815 V).

CoW Bimetallic Carbide Nanocatalysts: Computational Exploration, Confined Disassembly-Assembly Synthesis and Alkaline/Seawater Hydrogen Evolution

Earth-abundant tungsten carbide exhibits potential hydrogen evolution reaction (HER) catalytic activity owing to its Pt-like d-band electronic structure, which, unfortunately, suffers from the relatively strong tungsten-hydrogen binding, deteriorating its HER performance. Herein, a catalyst design concept of incorporating late transition metal into early transition metal carbide is proposed for regulating the metal-H bonding strength and largely enhancing the HER performance, which is employed to synthesize CoW bi-metallic carbide Co₆ W₆ C by a "disassembly-assembly" approach in a confined environment. Such synthesized Co₆ W₆ C nanocatalyst features the optimal Gibbs free energy of *H intermediate and dissociation barrier energy of H₂ O molecules as well by taking advantage of the electron complementary effect between Co and W species, which endows the electrocatalyst with excellent HER performance in both alkaline and seawater/alkaline electrolytes featuring especially low overpotentials, elevated current densities, and much-enhanced operation durability in comparison to commercial Pt/C catalyst. Moreover, a proof-of-concept Mg/seawater battery equipped with Co₆ W₆ C-2-600 as cathode offers a peak power density of 9.1 mW cm^-2 and an open-circuit voltage of ≈1.71 V, concurrently realizing hydrogen production and electricity output.

Robust Porous WC-Based Self-Supported Ceramic Electrodes for High Current Density Hydrogen Evolution Reaction

Developing an economical, durable, and efficient electrode that performs well at high current densities and is capable of satisfying large-scale electrochemical hydrogen production is highly demanded. A self-supported electrocatalytic "Pt-like" WC porous electrode with open finger-like holes is produced through industrial processes, and a tightly bonded nitrogen-doped WC/W (WC-N/W) heterostructure is formed in situ on the WC grains. The obtained WC-N/W electrode manifests excellent durability and stability under multi-step current density in the range of 30-1000 mA cm-2 for more than 220 h in both acidic and alkaline media. Although WC is three orders of magnitude cheaper than Pt, the produced electrode demonstrates comparable hydrogen evolution reaction performance to the Pt electrode at high current density. Density functional theory calculations attribute its superior performance to the electrode structure and the modulated electronic structure at the WC-N/W interface.

Trace Amount of NiP2 Cooperative CoMoP Nanosheets Inducing Efficient Hydrogen Evolution

As a very attractive clean energy, hydrogen has a high energy density and great potential to achieve zero pollution emission. Therefore, the preparation of hydrogen evolution electrocatalysts with excellent performance is an urgent task to ameliorate the global energy shortage and environmental pollution. Here, a trace amount of NiP₂ coupled with CoMoP nanosheets (NCMP) was synthesized by the one-step hydrothermal method and low-temperature phosphidation. Studies have found that although the dosage of NiP₂ is very low, its appearance has been efficient to improve the hydrogen evolution reaction (HER) performance of CoMoP, which may be induced by the synergistic effect of the two different components NiP₂ and CoMoP. To find the superior catalyst, the effect of Ni content on the catalyst performance is also studied, and it is found that when the dosage of Ni is 0.02 mM, NCMP-2 (2 means 0.02 mM) displays the most outstanding overpotential (10 mA cm^-2) of 46 mV.

Dual Metal-Loaded Porous Carbon Materials Derived from Silk Fibroin as Bifunctional Electrocatalysts for Hydrogen Evolution Reaction and Oxygen Evolution Reaction

Developing electrocatalysts with high efficiency and long-term stability for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is significant to massively generate hydrogen energy by water splitting. In this work, cobalt and tungsten dual metal-loaded N-doped porous carbon electrocatalysts derived from silk fibroin were successfully prepared through facile carbonization and chemical activation by KCl and applied as efficient electrocatalysts for HER and OER. After chemical activation, the resulting catalysts present a unique hierarchical porous structure with micro-, meso-, and macropores, which is able to expose more implantation sites for catalytic active metals and will in turn promote the efficient diffusion of the electrolyte. The catalyst under the optimized condition (CoW@ACSF) has a specific area of 326.01 m² g^-1. The overpotential at a current density of 10 mA cm ^-2 of CoW@ACSF is 138.42 ± 10.39 mV toward HER and 492.05 ± 19.04 mV toward OER. Furthermore, the overpotential only increases 101.2 mV toward HER and 66.00 mV toward OER after the long-term stability test of chronopotentiometric test over 10 h, which confirms the excellent stability of the CoW@ACSF, owing to its unique carbon shell structure. This work gives an insight into the design and engineering of silk fibroin-derived carbon materials for electrocatalysis toward HER and OER.

W Clusters In Situ Assisted Synthesis of Layered Carbon Nanotube Arrays on Graphene Achieving High-Rate Performance

W atoms/clusters are employed to in situ assist the development of layered vertically aligned carbon nanotube arrays (VACNTs) through hot-filament-assisted chemical vapor deposition (HFCVD) with liquid binary Fe₃O₄/AlO_x catalysts. The hot W filament was utilized to in situ evaporate atomic W and form W clusters on Fe catalysts, which have a strong impact on the growth of layered VACNT arrays. The migration and Ostwald ripening of Fe catalysts are found to be suppressed immediately with more W clusters deposition during CNT growth. Through controlling the deposition of W clusters, the electrochemical energy storage performance of as-prepared layered VACNT arrays is also tunable as electrodes of ion-based supercapacitors. The layered VACNT arrays can achieve a high capacity of 83.1 mF cm^-2 and possess desirable rate performance due to the suitable hot filament condition (55 W for 90 s). This work provides a new perspective to in-depth understand the behavior of W filament during HFCVD and the significant role of the in situ generated W clusters on the growth of CNTs by maintaining the catalytic activity and structure of catalysts.

Core-shell nanostructured electrocatalysts for water splitting

As the cornerstone of the hydrogen economy, water electrolysis consisting of the hydrogen and oxygen evolution reactions (HER and OER) greatly needs cost-efficient electrocatalysts that can decrease the dynamic overpotential and save on energy consumption. Over past years, observable progress has been made by constructing core-shell structures free from or with few noble-metals. They afford particular merits, e.g., a highly-exposed active surface, modulated electronic configurations, strain effects, interfacial synergy, or reinforced stability, to promote the kinetics and electrocatalytic performance of the HER, OER and overall water splitting. So far, a large variety of inorganics (carbon and transition-metal related components) have been introduced into core-shell electrocatalysts. Herein, representative efforts and progress are summarized with a clear classification of core and shell components, to access comprehensive insights into electrochemical processes that proceed on surfaces or interfaces. Finally, a perspective on the future development of core-shell electrocatalysts is offered. The overall aim is to shed some light on the exploration of emerging materials for energy conversion and storage.

W2C nanodot-decorated CNT networks as a highly efficient and stable electrocatalyst for hydrogen evolution in acidic and alkaline media

Although tungsten carbide (W2C) has long been reported as an excellent platinum-like catalyst, it is still a challenge to synthesize W2C as an electrocatalyst for a highly efficient hydrogen evolution reaction (HER) due to its high onset overpotential, inevitable aggregation, and lack of a scalable and controllable synthesis method. Herein, we synthesized W2C nanodot-decorated CNT networks (W2C@CNT-S) via a facile and scalable spray drying method followed by a carbonization process. It is demonstrated that this unique nanoarchitecture, constructed by ultrafine W2C nanodots homogeneously decorated on a three-dimensional and conductive CNT skeleton, leads to the exposure of abundant catalytic sites and promotes highly efficient electron transfer and ion diffusion during the HER process. As a result, in acidic and alkaline media, the optimized W2C@CNT-S hybrid exhibited excellent HER performance with very low onset overpotentials of only 60 and 40 mV (vs. RHE) and very small Tafel slopes of 57.4 and 56.2 mV dec-1, and only needed 176 and 148 mV (vs. RHE) to obtain a current density of 10 mA cm-2, respectively; it also showed outstanding long-term durability even after a 30-hour test in both acidic and alkaline media. This study presents an overview of a low-cost and scalable spray-drying strategy to synthesize a high-performance carbide-based electrocatalyst for hydrogen evolution.

Flowerlike NiCo2S4 Hollow Sub-Microspheres with Mesoporous Nanoshells Support Pd Nanoparticles for Enhanced Hydrogen Evolution Reaction Electrocatalysis in Both Acidic and Alkaline Conditions

Flowerlike NiCo₂S₄ hollow sub-microspheres are synthesized through Cu₂O templates to support Pd nanoparticles as high-efficiency catalysts for the hydrogen evolution reaction (HER). The diameter and shell size of NiCo₂S₄ hollow sub-microspheres are about 400 and 16 nm, respectively. In addition, the surface of the shells is constructed by petallike nanosheets. About 3 nm Pd particles uniformly incorporate with the flowerlike NiCo₂S₄ hollow sub-microsphere to form the NiCo₂S₄/Pd heterostructure. The NiCo₂S₄/Pd catalysts exhibit significantly lower overpotential of only 87 and 83 mV at 10 mA/cm² for the HER in both acidic and alkaline conditions, respectively, relative to NiCo₂S₄ (247, 226 mV) and Pd (175, 385 mV) catalysts. Besides, the NiCo₂S₄/Pd catalysts also exhibit excellent stability of HER in these two conditions. The superior HER performance of NiCo₂S₄/Pd might be resulted from the unique architecture of metal nanoparticles anchored on the bimetallic sulfide flowerlike hollow sub-microspheres, which could provide high surface area, lots of active sites, strong synergetic effect, and stable structure.