Liquid nitrogen quenching inducing lattice tensile strain to endow nitrogen/fluorine co-doping Fe3O4 nanocubes assembled on porous carbon with optimizing hydrogen evolution reaction

Strain trailing band engineering and phonon transport of high ZT ZrCoBi half-Heusler alloy: a mechanistic understanding from first principles

Enhancing the thermoelectric (TE) performance of materials requires simultaneous optimization of the power factor (PF) and reduction of thermal conductivity (κ), a challenging task due to their interdependent nature. This work demonstrates a concurrent enhancement of PF and reduction of κ in p-type half-Heusler compound, ZrCoBi. Using ab initio electronic structure calculations, we investigate the impact of isotropic tensile and compressive strains on the TE properties of materials. Our analysis encompasses electronic structure, mechanical properties, lattice dynamics, Seebeck coefficient, electrical and thermal conductivity, PF, and the figure of merit (ZT). The results reveal a unique strain-dependent behavior in the electronic properties of ZrCoBi, including a spurious band convergence effect, as identified through first-principles calculations incorporating spin-orbit coupling (SOC). Furthermore, the analysis shows that tensile strain effectively tunes the band gap, significantly altering the electronic structure and improving PF. At the same time, tensile strain induces significant changes in lattice dynamics, reducing lattice thermal conductivity (κL). These combined effects result in a fourfold increase in ZT at high temperatures. This study also provides a comprehensive framework for leveraging isotropic strain to achieve high-performance thermoelectric materials and guides the experimental exploration of enhanced ZT compounds.

Liquid nitrogen quenching for efficient Bifunctional electrocatalysts in water Splitting: Achieving four key objectives in one step

Herein, a novel liquid nitrogen quenching treatment is proposed to achieve multifaceted modulation involving morphological modulation, lattice tensile strain modulation, metal active centre coordination reconstruction and grain boundary construction within a series of intermetallic compounds modified on a carbon substrate (CoFe-550/C, CoNi-550/C and FeNi3-550/C, where 550 refers to liquid nitrogen quenching temperature and C refers to the carbon substrate). Noteworthily, the optimising intermediate absorption/desorption process is achieved by multifaceted modulation. Consequently, CoFe-550/C, CoNi-550/C and FeNi3-550/C demonstrate considerable overpotential for hydrogen evolution reaction (59.5, 74.5 and 94.5 mV at - 10 mA cm-2) and oxygen evolution reaction (312.5, 365.5 and 333.5 mV at 10 mA cm-2) in an alkaline electrolyte and overpotentials for hydrogen evolution reaction (66.5, 81.5 and 106.5 mV at - 10 mA cm-2) in simulated seawater with 1.0 M KOH + 0.5 M NaCl (89.5, 97.5 and 115.5 mV in 0.5 M NaCl), respectively. In addition, the CoFe-, CoNi- and FeNi3-based electrolysers exhibit prominent overall water-splitting activity in an alkaline environment (1.59, 1.77 and 1.69 V, respectively) at 10 mA cm-2. Overall, the proposed liquid nitrogen quenching strategy opens up new possibilities for obtaining highly active electrocatalysts for the new generation of green energy conversion systems.

Strain Engineering for Electrocatalytic Overall Water Splitting

Strain engineering is a novel method that can achieve superior performance for different applications. The lattice strain can affect the performance of electrochemical catalysts by changing the binding energy between the surface-active sites and intermediates and can be affected by the thickness, surface defects and composition of the materials. In this review, we summarized the basic principle, characterization method, introduction strategy and application direction of lattice strain. The reactions on hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) are focused. Finally, the present challenges are summarized, and suggestions for the future development of lattice strain in electrocatalytic overall water splitting are put forward.

Iron-Cobalt Nanoparticles Embedded in B,N-Doped Chitosan-Derived Porous Carbon Aerogel for Overall Water Splitting

Given their intriguing properties, porous carbons have surfaced as promising electrocatalysts for various energy conversion reactions. This study presents a unique approach where iron-cobalt (FeCo) is confined in a boron, nitrogen-doped chitosan-derived porous carbon aerogel (BNPC-FeCo) to serve as an electrocatalyst for the hydrogen evolution and oxygen evolution reactions (HER and OER). The BNPC-FeCo-900 electrocatalyst demonstrates excellent catalyst activity, with very low overpotentials of 186 and 320 mV at 10 mA cm-2, low Tafel slopes of 82 and 55 mV dec-1, and low charge transfer resistance of 2.68 and 9.25 Ω for HER and OER, respectively. Density functional theory (DFT) calculations further reveal that the cooperation between the boron, nitrogen codoped porous carbon, and the FeCo nanoparticles reduces intermediates' energy barriers, significantly enhancing the HER and OER performance. In conclusion, this work offers significant and informative perspectives into the potential of porous carbon materials as dual-purpose electrocatalysts for water splitting.

Evolution of Grain Boundaries Promoted Hydrogen Production for Industrial-Grade Current Density

The development of efficient and durable high-current-density hydrogen production electrocatalysts is crucial for the large-scale production of green hydrogen and the early realization of hydrogen economic blueprint. Herein, the evolution of grain boundaries through Cu-mediated NiMo bimetallic oxides (MCu-BNiMo), which leading to the high efficiency of electrocatalyst for hydrogen evolution process (HER) in industrial-grade current density, is successfully driven. The optimal MCu0.10-BNiMo demonstrates ultrahigh current density (>2 A cm-2) at a smaller overpotential in 1 m KOH (572 mV), than that of BNiMo, which does not have lattice strain. Experimental and theoretical calculations reveal that MCu0.10-BNiMo with optimal lattice strain generated more electrophilic Mo sites with partial oxidation owing to accelerated charge transfer from Cu to Mo, which lowers the energy barriers for H* adsorption. These synergistic effects lead to the enhanced HER performance of MCu0.10-BNiMo. More importantly, industrial application of MCu0.10-BNiMo operated in alkaline electrolytic cell is also determined, with its current density reached 0.5 A cm-2 at 2.12 V and 0.1 A cm-2 at 1.79 V, which is nearly five-fold that of the state-of-the-art HER electrocatalyst Pt/C. The strategy provides valuable insights for achieving industrial-scale hydrogen production through a highly efficient HER electrocatalyst.