Recent advances in transition metal nitrides for hydrogen electrocatalysis in alkaline media: From catalyst design to application

Core-shell Ru@Co2P synergistic catalyst as polysulfides adsorption-catalytic conversion mediator with enhanced redox kinetics in lithium-sulfur batteries

Lithium-sulfur batteries (LSBs) have emerged as the research hotspot due to their compelling merits, including high specific capacity (1675 mAh g-1), theoretical energy density (2600 Wh kg-1), environmental friendliness, and economic advantages. However, challenges still exist for further application due to their inherent issues such as the natural insulation, shuttle effect, and volume expansion of sulfur cathode during the continuous cycle processes. These factors obstruct the lithium ions (Li+) transfer process and sulfur utilization, resulting in significant impedance and inducing inferior battery performance. Herein, the core-shell nanocube anchoring ruthenium atoms and dicobalt phosphate (Ru@Co2P@NC) were fabricated as the effective catalyst and inhibited barrier for LSBs. On the one hand, the core-shell structure offers numerous channels to expedite Li+ diffusion. On the other hand, ruthenium (Ru) and dicobalt phosphate (Co2P) active sites facilitate the chemical capture of lithium polysulfides (LiPSs), accelerating sluggish kinetics. Ru@Co2P@NC modified cells not only exhibited a high initial specific capacity (1609.35 mAh g-1) at 0.5C and enduring stability with high specific capacity retention of 906.60 mAh g-1 at 0.5C after 400 cycles but also possessed low capacity attenuation rate of 0.07 % per cycle after 600 cycles (1C, Sulfur loading: 1.2 mg). Interestingly, the modified cells demonstrated a high specific capacity and long-cycle stability with high sulfur loading (from 1.984 to 3.137 mg), which provides a promising research approach for high-performance LSBs.

Microscopic Insight into the Polarization-Dependent Oxygen Evolution Reaction on the Surface of Intrinsic Ferroelectric Semiconductor β-CuGaO2

Ferroelectric semiconductors hold great promise in the field of photocatalysis due to their spontaneous polarization that can suppress the recombination of photogenerated charges, but the mechanism of the effect of ferroelectric polarization and the intensity of polarization on surface catalytic reactions have never been approached. Here, we have comparatively investigated the oxygen evolution reaction (OER) catalytic process on surfaces in polarized and unpolarized orientations of the intrinsic ferroelectric semiconductor β-CuGaO2 by first-principles calculations. Furthermore, semiquantitative effects of different polarization intensities on the OER on the surfaces are subsequently carried out. First, it is confirmed that the [011]-polarized surface with fully exposed Cu-O atoms is the easiest surface to form and the most attractive for water molecules, exhibiting the lowest OER free energy barrier of 1.71 eV. Second, the calculated results indicate that [011] surfaces with higher polarization intensity are capable of enhancing the photogenerated hole potential (U) due to the accumulation of microscopic polarization in the polar unit of the bulk phase within the [011] slab. The intrinsic mechanism behind the enhancement of the OER by ferroelectric polarization is attributed to the modulation effect of polarization intensity on the 3d orbit of Cu+. This work elucidates the effects of ferroelectric polarization orientations as well as polarization intensity for the water OER, and provides theoretical guidance for the intrinsic ferroelectric polarization to promote surface OER.

Ultrafine nickel-rhodium nanoparticles anchored on two-dimensional vanadium carbide for high performance hydrous hydrazine decomposition at mild conditions

The development of heterogeneous supported nanocatalysts with a high kinetics combined with low cost is off importance but remains still challenged for hydrazine hydrate served as a promising hydrogen storage material. Herein, by virtue of surficial functional groups, ultrafine NiRh NPs were monodispersed on the two-dimensional V2C surface via a conventional wet chemical co-reduction. The optimized NiRh/V2C system demonstrates an excellent catalytic performance toward selectively catalyzing dehydrogenation of hydrazine hydrate, affording 100% H2 selectivity with the turnover frequency (TOF) value of 987.5 h-1 at 323 K. Such an enhancement is mainly attributed to synergistic effect of nanosystem, which will optimize local surface energy and promote electron transfer in NiRh/V2C system, thereby improving the kinetic selectivity of catalytic hydrazine hydrate decomposition. This work has provided a facile strategy for developing nanocatalysts with high kinetics that could enable huge industrial applications in the future.

Universal Copolymerization of Crosslinked Polyether Electrolytes for All-Solid-State Lithium-Metal Batteries

Solid polymer electrolytes (SPEs) are pivotal in advancing the practical implementation of all-solid-state batteries. Poly(1,3-dioxane) (PDOL)-based electrolytes have attracted significant attention due to the pseudo-high conductivity achieved through sophisticated in situ polymerization methods; however, such PDOL-based electrolytes present challenges of crystallization over time and monomers residual during processing. In this study, integrating LiTFSI and LiDFOB as a universal copolymerization strategy for developing high-performance PDOL electrolytes with a wide range of epoxy crosslinkers is proposed. It is discovered that this approach leverages the protective effects of TFSI anions on the boron active center and catalyzes polymer chain growth via crosslinking. The homogenously crosslinked (benzene-centered) PDOL electrolyte exhibits remarkable thermo-mechanical stability (up to 100 °C), high ion migration number (tLi+ = 0.42), a wide electrochemical window (≈5.0 V vs Li+/Li), and high ionic conductivity (4.5×10-4 S cm-1). Notably, the crosslinked PDOL electrolyte is in the all-solid-state with minimal monomer/oligomer residual, exhibiting no crystallization during relaxation, delivering a robust performance in all-solid-state lithium metal batteries.

Interfacial Electronic Modulation of Mo5N6/Ni3S2 Heterojunction Array Boosts Electrocatalytic Alkaline Overall Water Splitting

Bifunctional electrocatalysts with excellent activity and durability are highly desirable for alkaline overall water splitting, yet remain a significant challenge. In this contribution, palm-like Mo5N6/Ni3S2 heterojunction arrays anchored in conductive Ni foam (denoted as Mo5N6-Ni3S2 HNPs/NF) are developed. Benefiting from the optimized electronic structure configuration, hierarchical branched structure and abundant heterogeneous interfaces, the as-synthesized Mo5N6-Ni3S2 HNPs/NF electrode exhibits remarkably stable bifunctional electrocatalytic activity in 1 m KOH solution. It only requires ultralow overpotentials of 59 and 190 mV to deliver a current density of 10 mA cm-2 for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in 1 m KOH solution, respectively. Importantly, the overall water splitting electrolyzer assembled by Mo5N6-Ni3S2 HNPs/NF exhibits an exceptionally low cell voltage (1.48 V@10 mA cm-2) and outstanding durability, surpassing most of the reported Ni-based bifunctional materials. Density functional theory (DFT) further confirms the heterostructure can optimize the Gibbs free energies of H and O-containing intermediates (OH, O, OOH) during HER and OER processes, thereby accelerating the catalytic kinetics of electrochemical water splitting. The findings provide a new design strategy toward low-cost and excellent catalysts for overall water splitting.

Nitrided Rhodium Nanoclusters with Optimized Water Bonding and Splitting Effects for pH-Universal H2-Production

The nitridation of noble metals-based catalysts to further enhance their hydrogen evolution reaction (HER) kinetics in neutral and alkaline conditions would be an effective strategy for developing high-performance wide pH HER catalysts. Herein, a facile molten urea method is employed to construct the nitrided Rh nanoclusters (RhxN) supported on N-doped carbon (RhxN-NC). The uniformly distributed RhxN clusters exhibited optimized water bonding and splitting effects, therefore resulting in excellent pH-universal HER performance. The optimized RhxN-NC catalyst only requires 8, 12, and 109 mV overpotentials to reach the current density of 10 mA cm-2 in 0.5 M H2SO4, 1.0 M KOH, and 1.0 M PBS electrolytes, respectively. The spectroscopic characterizations and theoretical calculation further confirm the vital role of Rh-N moieties in RhxN clusters in improving the transfer of electrons and facilitating the generation of H2. This work not only provides a suitable nitridation method for noble metal species in mild conditions but also makes a breakthrough in synthesizing noble metal nitrides-based electrocatalysts to achieve an exceptional wide-pH HER performance and other catalysis.

A defect-enriched PdMo bimetallene for ethanol oxidation reaction and 4-nitrophenol reduction

A defect-enriched PdMo bimetallene (d-PdMo) was prepared by a one-pot wet chemical reaction followed by post-treatment of oxidative etching. The introduction of defects can tailor the electronic structure of PdMo bimetallene and the prepared d-PdMo bimetallene exhibited excellent performance in the ethanol oxidation reaction (EOR) and 4-nitrophenol (4-NP) reduction reaction.

Laser-induced immobilization of an amorphous iron-phosphate/Fe3O4 composite on nickel foam for efficient water oxidation

A laser-induced immobilization strategy is applied to prepare an amorphous iron-phosphate/Fe3O4 (L-FePO) composite on a nickel foam (NF) support. By laser-irradiating an iron hydrogen phosphate (FeHP) precursor, a melting and oxidation process leads to the generation of L-FePO with hierarchical pores and an amorphous structure. L-FePO shows exceptional electrocatalytic performance for the OER in an alkaline electrolyte, demonstrating an overpotential of 256 mV at 100 mA cm-2, a Tafel slope of 71 mV dec-1, and good stability over 100 h. The active Fe3O4, partially dissolved phosphate, and newly formed FeOOH species provide abundant active sites, contributing to the excellent OER performance.

Interface Catalysts of Ni3Fe1 Layered Double Hydroxide and Titanium Carbide for High-Performance Water Oxidation in Alkaline and Natural Conditions

The electrocatalytic oxygen evolution reaction (OER) is important for many renewable energy technologies. Developing cost-effective electrocatalysts with high performance remains a great challenge. Here, we successfully demonstrate our novel interface catalyst comprised of Ni₃Fe₁-based layered double hydroxides (Ni₃Fe₁-LDH) vertically immobilized on a two-dimensional MXene (Ti₃C₂T_x) surface. The Ni₃Fe₁-LDH/Ti₃C₂T_x yielded an anodic OER current of 100 mA cm^-2 at 0.28 V versus reversible hydrogen electrode (RHE), nearly 74 times lower than that of the pristine Ni₃Fe₁-LDH. Furthermore, the Ni₃Fe₁-LDH/Ti₃C₂T_x catalyst requires an overpotential of only 0.31 V versus RHE to deliver an industrial-level current density as high as 1000 mA cm^-2. Such excellent OER activity was attributed to the synergistic interface effect between Ni₃Fe₁-LDH and Ti₃C₂T_x. Density functional theory (DFT) results further reveal that the Ti₃C₂T_x support can efficiently accelerate the electron extraction from Ni₃Fe₁-LDH and tailor the electronic structure of catalytic sites, resulting in enhanced OER performance.