FeCoCuMnRuB Nanobox with Dual Driving of High-Entropy and Electron-Trap Effects as the Efficient Electrocatalyst for Water Oxidation

Nonmetallic High-Entropy-Engineered Nanocarbons for Advanced ORR Electrocatalysis

High-entropy materials are poised to revolutionize materials science and industrial applications due to their design flexibility, peculiar performance, and broad applicability. In this study, we present a proof-of-concept high-entropy engineered nanocarbon (HENC) co-doped with five nonmetal elements (B, F, P, S, and N), synthesized via in situ polymerization modification of ZIF-8 followed by pyrolysis. The HENC exhibits outstanding performance as a nonmetal electrocatalyst for the oxygen reduction reaction (ORR), with activity on par with benchmark Pt/C electrocatalysts and superior cyclic stability. Simulations and all-site calculations reveal that the synergistic effects of abundant heteroatoms and increased system entropy facilitate the formation of *O2 species, with N, P, and S acting as the key active elements, while co-doping with B and F further enhances stability. Notably, HENCs have been validated as cathode catalysts in zinc-air batteries, achieving an impressive peak power density of 604 mW cm-2 and demonstrating long-term stability over a 16-day period, outpacing the commercial Pt/C catalyst (542 mW cm-2). This work not only enriches the concept of high entropy and advances the understanding of high-entropy materials but also opens a new avenue for the development of high-performance low-cost catalysts.

Non-precious metal high-entropy alloys for CO2 electroreduction

Non-precious metal high-entropy alloys (HEAs) with the merits of low cost for effective CO2 reduction reaction (CO2RR) are still in their infancy. In this work, we prepared the non-precious CuCoAlFeNi HEA using a solvothermal method. The prepared CuCoAlFeNi HEA showed a homogeneous element distribution in the solid solution structure. Compared to the C1 product (HCOOH) yielded by Cu nanoparticles in an H-type cell, the CuCoAlFeNi HEA presented a Faraday efficiency of 36.56% towards the C2 product (CH3CH2OH). In situ Raman measurements revealed the CO2RR intermediates and the corresponding reaction pathway. In addition, the CuCoAlFeNi HEA catalyst exhibited superior electrochemically catalytic stability and reusability. This work demonstrates the selectivity towards C2 products, stability, and reusability of CuCoAlFeNi HEA, presenting the potential application of non-precious metal HEAs in CO2RR.

In situ evolved high-valence Co active sites enable highly efficient and stable chlorine evolution reaction

The chlor-alkali process is crucial in the modern chemical industry, yet it is highly energy-intensive, consuming about 4 % of global electricity due to the significant overpotential and low selectivity of existing chlorine evolution reaction (CER) electrocatalysts. Although advanced electrocatalysts have reduced the energy demands of the chlor-alkali process, they typically incorporate precious metals. Here, we introduce a novel precious metal-free electrocatalyst, (CoZn)3V2O8@C, with a hollow nanocube structure that exhibits outstanding CER performance. It features an overpotential of just 69 mV, a selectivity exceeding 90 %, and a high durability of 250 h at a current density of 10 mA/cm2, surpassing commercial dimensionally stable anodes (DSA) and some precious metal-based electrocatalysts. Comparative experiments and physical characterizations reveal that during the CER, high-valence Co evolves in situ due to the formation of adjacent Zn vacancies from the partial dissolution of Zn in (CoZn)3V2O8@C. Density functional theory further confirms that Zn vacancies can modify the electronic structure of the adjacent Co, enhancing the adsorption and activation of chloride ions, reducing the energy barrier of the reaction, and thereby improving the catalytic performance of CER.

A(CoFe)(S2)2/CoFe heterostructure constructed in S, N co-doped carbon nanotubes as an efficient oxygen electrocatalyst for zinc-air battery

Transition metal alloys can exhibit synergistic intermetallic effects to obtain high activities for oxygen reduction/evolution reactions (ORR/OER). However, due to the insufficient stability of active sites in alkaline electrolytes, conventional alloy catalysts still do not meet practical needs. Herein, by using polypyrrole tubes and cobalt-iron (CoFe) Prussian blue analogs as precursors, CoFe sulfides is in-situ formed on CoFe alloys to construct (CoFe)(S2)2/CoFe heterostructure in sulfur (S) and nitrogen (N) co-doped carbon nanotubes (CoFe@NCNTs-nS) via a low-temperature sulfidation strategy. The as-marked CoFe@NCNTs-12.5S exhibits a comparable ORR activity (half-wave potential of 0.901 V) to Pt/C (0.903 V) and a superior OER activity (overpotential of 272 mV at 10 mA cm-2) to RuO2 (299 mV). CoFe@NCNTs-12.5S also exhibits ultralow charge transfer resistances (ORR-6.36 Ω and OER-0.21 Ω) and an excellent potential difference of 0.617 V. The sulfidation-induced (CoFe)(S2)2/CoFe heterojunctions can accelerate interfacial charge transfer process. Tubular structure not only disperses the (CoFe)(S2)2/CoFe heterostructure, but also reduces the corrosion of active-sites to enhance catalysis stability. Zinc-air battery with CoFe@NCNTs-12.5S achieves a high specific capacity (718.1 mAh g-1), maintaining a voltage gap of 0.957 V after 400 h. This work reveals the potential of interface engineering for boosting ORR/OER activities of alloys via in-situ heterogenization.

Spiral-Concave Prussian Blue Crystals with Rich Steps: Growth Mechanism and Coordination Regulation

Investigating the formation and transformation mechanisms of spiral-concave crystals holds significant potential for advancing innovative material design and comprehension. We examined the kinetics-controlled nucleation and growth mechanisms of Prussian Blue crystals with spiral concave structures, and constructed a detailed crystal growth phase diagram. The spiral-concave hexacyanoferrate (SC-HCF) crystals, characterized by high-density surface steps and a low stress-strain architecture, exhibit enhanced activity due to their facile interaction with reactants. Notably, the coordination environment of SC-HCF can be precisely modulated by the introduction of diverse metals. Utilizing X-ray absorption fine structure spectroscopy and in situ ultraviolet-visible spectroscopy, we elucidated the formation mechanism of SC-HCF to Co-HCF facilitated by oriented adsorption-ion exchange (OA-IE) process. Both experimental data, and density functional theory confirm that Co-HCF possesses an optimized energy band structure, capable of adjusting the local electronic environment and enhancing the performance of the oxygen evolution reaction. This work not only elucidates the formation mechanism and coordination regulation for rich steps HCF, but also offers a novel perspective for constructing nanocrystals with intricate spiral-concave structures.

Edge-Rich 3D Structuring of Metal Chalcogenide/Graphene with Vertical Nanosheets for Efficient Photocatalytic Hydrogen Production

Constructing pertinent nanoarchitecture with abundant exposed active sites is a valid strategy for boosting photocatalytic hydrogen generation. However, the controllable approach of an ideal architecture comprising vertically standing transition metal chalcogenides (TMDs) nanosheets on a 3D graphene network remains challenging despite the potential for efficient photocatalytic hydrogen production. In this study, we fabricated edge-rich 3D structuring photocatalysts involving vertically grown TMDs nanosheets on a 3D porous graphene framework (referred to as 3D Gr). 2D TMDs (MoS2 and WS2)/3D Gr heterostructures were produced by location-specific photon-pen writing and metal-organic chemical vapor deposition for maximum edge site exposure enabling efficient photocatalytic reactivity. Vertically aligned 2D Mo(W)S2/3D Gr heterostructures exhibited distinctly boosted hydrogen production because of the 3D Gr caused by synergetic impacts associated with the large specific surface area and improved density of exposed active sites in vertically standing Mo(W)S2. The heterostructure involving graphene and TMDs corroborates an optimum charge transport pathway to rapidly separate the photogenerated electron-hole pairs, allowing more electrons to contribute to the photocatalytic hydrogen generation reaction. Consequently, the size-tailored heterostructure showed a superior hydrogen generation rate of 6.51 mmol g-1 h-1 for MoS2/3D graphene and 7.26 mmol g-1 h-1 for WS2/3D graphene, respectively, which were 3.59 and 3.76 times greater than that of MoS2 and WS2 samples. This study offers a promising path for the potential of 3D structuring of vertical TMDs/graphene heterostructure with edge-rich nanosheets for photocatalytic applications.

Explosive Leidenfrost-Droplet-Mediated Synthesis of Monodispersed High-Entropy-Alloy Nanoparticles for Electrocatalysis

High-entropy-alloy nanoparticles (HEA NPs) exhibit promising potential in various catalytic applications, yet a robust synthesis strategy has been elusive. Here, we introduce a straightforward and universal method, involving the microexplosion of Leidenfrost droplets housing carbon black and metal salt precursors, to fabricate PtRhPdIrRu HEA NPs with a size of ∼2.3 nm. The accumulated pressure within the Leidenfrost droplet triggers an intense explosion within milliseconds, propelling the carbon support and metal salt rapidly into the hot solvent through explosive force. The exceptionally quick temperature rise ensures the coreduction of metal salts, and the dilute local concentration of metal ions limits the final size of the HEA NPs. Additionally, the explosion process can be fine-tuned by selecting different solvents, enabling the harvesting of diverse HEA NPs with superior electrocatalytic activity for alcohol electrooxidation and hydrogen electrocatalysis compared to commercial Pt (Pd) unitary catalysts.

Sublayer-Sulfur-Vacancy-Induced Charge Redistribution of FeCuS Nanoflower Awakening Alkaline Hydrogen Evolution

Advancing the progress of sustainable and green energy technologies requires the improvement of valid electrocatalysts for the hydrogen evolution reaction (HER). Reconfiguring charge distribution through heteroatom doping-induced vacancy serves as an effective approach to implement high performance for HER catalysts. Here, we successfully fabricated Fe-doped CuS (FeCuS) with the sublayer sulfur vacancy to judge its HER performance and dissect the activity origins. Density functional theory calculation further elucidates that the primary factor contributing to the heightened HER activity is that the sublayer sulfur vacancies awaken the charge redistribution. In addition to effectively decreasing the energy barrier associated with the Volmer step, it modulates the adsorption/desorption capacity of H*. As a result, its intrinsic activity for the HER has significantly increased. Concretely, the obtained FeCuS displays an excellent catalytic performance, whose Tafel slope is only 59 mV dec-1 and the overpotential (at 10 mA cm-2) is as low as 71 mV in an alkaline environment, surpassing the majority of previously documented catalysts in scientific literature. This work shows that the construction of sublayer sulfur vacancies by Fe doping can achieve the charge redistribution and precise tuning of electronic structure; thereby, the inert CuS can be transformed into highly efficient electrocatalysts.