H₂TiO₃ (HTO) emerges as a highly promising lithium-ion sieve (LIS) material for selectively and efficiently extracting lithium from liquid-phase systems. However, the practical use of conventional powdered HTO adsorbents is hindered by difficulties in recovery and titanium leaching, which limits their reusability. Herein, we design a novel HTO/MXene/polysulfone (HTO/MXene/PSF) hybrid membrane, where two-dimensional (2D) MXene nanosheets bridge PSF and HTO via enhanced hydrogen bonding and enable the in-situ self-assembly of HTO into spindle-like nanostructures. As anticipated, the hybrid membrane exhibits selective lithium adsorption, achieving a capacity of 25.80 mg·g⁻¹ from shale gas wastewater (SGW). Moreover, it maintains remarkable cyclic stability with a negligible decrease in adsorption capacity of merely 0.25% after ten consecutive adsorption–desorption cycles. Besides, filtration studies demonstrate that a membrane with a surface area of 12.56 cm² can effectively process 230 mL of SGW. Theoretical calculations reveal that hydrogen bonding and electronic interactions drive the self-assembly of HTO on MXene and further elucidate the adsorption strength and spatial hindrance mechanisms for selective lithium ion adsorption. This study introduces an innovative concept of in-situ self-assembled LIS in a hybrid membrane for lithium recovery from SGW, which is expected to inspire further research on self-assembled sieve-based adsorbents.

Water-soluble nitrite (NO₂⁻) in wastewater from agricultural and industrial activities poses ecological and health risks, and its electroreduction shows promise for ammonia (NH₃) production, but energy losses from the hydrogen evolution reaction (HER) limit its overall efficiency. In this work, we report the use of CoFe-layered double hydroxides on 3D TiO₂ array (TiO₂@CoFe-LDH/TP) as an effective electrocatalyst for NO₂⁻ reduction. By offering superior *H species supply and hydroprocessing capability, this catalyst achieves an NH₃ yield of 1056.4 μmol h⁻¹ cm⁻² with a 97.4% Faradaic efficiency (FE) at −0.6 V and sustains FE above 87% across a range of applied potentials. Additionally, a 60-h simulated wastewater treatment experiment demonstrates its practical application potential.

Fabricating catalysts with efficient water dissociation and robust stability is key to advancing the industrialization of the alkaline hydrogen evolution reaction (HER). Establishing an effective phosphide/oxide interface is a feasible way to improve the HER performance of the catalyst in an alkaline medium, but it remains challenging. Here, we adopt that manganese oxide nanoparticles decorated on nickel-cobalt phosphide nanowire array on nickel foam (MnO_x@NiCoP/NF) via a surface modification strategy that shifts the d-band center downward, promoting the water dissociation and hydrogen intermediate binding. Moreover, MnO_x makes the surface of NiCoP rougher, facilitating bubble release and improving the array stability. Consequently, MnO_x@NiCoP/NF achieves industrial current densities of 500 and 1000 mA·cm⁻² with overpotentials of 171 and 193 mV, respectively, while maintaining stable operation for over 600 h at 1000 mA·cm⁻² in 1 M KOH. Additionally, an anion exchange membrane electrolyzer with the catalyst was fabricated and shows potential for practical applications.

It is of great importance to design and develop electrocatalysts that are both long-lasting and efficient for seawater oxidation. Herein, a three-dimensional porous cauliflower-like Ni₃S₂ foam on Ni foam (Ni₃S₂ foam/NF) is proposed as a high-performance electrocatalyst for the oxygen evolution reaction in alkaline seawater. The as-synthesis Ni₃S₂ foam/NF achieves exceptional efficacy, achieving a current density of 100 mA·cm⁻² at mere overpotential of 369 mV. Notably, its electrocatalytic stability extends up to 1000 h at 500 mA·cm⁻².

Seawater electrolysis, especially in coastlines, is widely considered as a sustainable way of making clean and high-purity H₂ from renewable energy; however, the practical viability is challenged severely by the limited anode durability resulting from side reactions of chlorine species. Herein, we report an effective Cl⁻ blocking barrier of NiFe-layer double hydroxide (NiFe-LDH) to harmful chlorine chemistry during alkaline seawater oxidation (ASO), a pre-formed surface-derived NiFe-phosphate (Pi) outer-layer. Specifically, the PO₄³⁻-enriched outer-layer is capable of physically and electrostatically inhibiting Cl⁻ adsorption, which protects active Ni³⁺ sites during ASO. The NiFe-LDH with the NiFe-Pi outer-layer (NiFe-LDH@NiFe-Pi) exhibits higher current densities (j) and lower overpotentials to afford 1 A·cm⁻² (η₁₀₀₀ of 370 mV versus η₁₀₀₀ of 420 mV) than the NiFe-LDH in 1 M KOH + seawater. Notably, the NiFe-LDH@NiFe-Pi also demonstrates longer-term electrochemical durability than NiFe-LDH, attaining 100-h duration at the j of 1 A·cm⁻². Additionally, the importance of surface-derived PO₄³⁻-enriched outer-layer in protecting the active centers, γ-NiOOH, is explained by ex situ characterizations and in situ electrochemical spectroscopic studies.

Advancing efficient and affordable electrocatalysts to boost the oxygen evolution reaction (OER) is pivotal for sustainable green hydrogen production. Herein, we propose the fabrication of nickel-iron alloy nanoparticles-encapsulated on N-doped vertically aligned graphene array on carbon cloth (NiFe@NVG/CC) as a highly active three-dimensional (3D) catalyst electrode for OER. In 1 M KOH, such NiFe@NVG/CC demonstrates outstanding catalytic performance, necessitating merely overpotential of 245 mV for achieving a current density of 10 mA·cm⁻², a remarkably low Tafel slope of 36.2 mV·dec⁻¹. Furthermore, density functional theory calculations validate that the incorporate of N species into graphene can reinforce the electrocatalytic activity though reducing the reaction energy barrier during the conversion of *O to *OOH intermediates. The outstanding performance and structural benefits of NiFe@NVG/CC offer valuable insights for the development of innovative and efficient electrocatalysts for water oxidation.

Nitrate (NO₃⁻), a nitrogen-containing pollutant, is prevalent in aqueous solutions, contributing to a range of environmental and health-related issues. The electrocatalytic reduction of NO₃⁻ holds promise as a sustainable approach to both eliminating NO₃⁻ and generating valuable ammonia (NH₃). Nevertheless, the reduction reaction of NO₃⁻ (NO₃⁻RR), involving 8-electron transfer process, is intricate, necessitating highly efficient electrocatalysts to facilitate the conversion of NO₃⁻ to NH₃. In this study, Fe-doped Co₃O₄ nanowire strutted three-dimensional (3D) pinewood-derived carbon (Fe-Co₃O₄/PC) is proposed as a high-efficiency NO₃⁻RR electrocatalyst for NH₃ production. Operating within 0.1 M NaOH containing NO₃⁻, Fe-Co₃O₄/PC demonstrates exceptional performance, obtain an impressively large NH₃ yield of 0.55 mmol·h⁻¹·cm⁻² and an exceptionally high Faradaic efficiency of 96.5% at −0.5 V, superior to its Co₃O₄/PC counterpart (0.2 mmol·h⁻¹·cm⁻², 73.3%). Furthermore, the study delves into the reaction mechanism of Fe-Co₃O₄ for NO₃⁻RR through theoretical calculations.

Nitrate (NO₃⁻) removal by photochemical-reduction has received extensive attention. However, the low selectivity of NO₃⁻ reduction to N₂ hinders the application of this technology. In this study, a novel Cu@Fe-Cu-CuFe₂O_4−x photocatalyst was prepared by modifying CuFe₂O₄ with KBH₄ and Cu(II), and used to selectively reduce NO₃⁻ to N₂ with a two-step reduction process. In step (1), with Cu@Fe-Cu-CuFe₂O_4−x/ultraviolet (UV) system, 91.0% NO₃⁻ was reduced to 52.3% NO₂⁻ and 39.4% N₂ within 60 min. The rapid removal of NO₃⁻ was due to the synergistic effect of oxygen vacancies, Fe-Cu corrosion cell, and CuFe₂O₄ photocatalysis. In step (2), H₂C₂O₄ and H₂O₂ were introduced into the effluent of step (1) to promote CO₂·⁻ formation via Fe(II) and Fe(III) catalysis and UV radiation, which boosted the selective reduction of NO₂⁻ to N₂. When H₂C₂O₄ and H₂O₂ dosages were both 4.0 mmol·L⁻¹ and the reaction time was 30 min, the removal efficiency of NO₂⁻ achieved 100% and the selectivity of N₂ was 83.0%. Overall, the two-step reduction process achieved 95.0% NO₃⁻ removal efficiency and 90.1% N₂ selectivity with initial NO₃⁻ concentration of 30 mg·N·L⁻¹. In addition, the denitrification mechanism of the two-step reduction process was tentatively proposed.

Seawater electrolysis is an extremely attractive approach for harvesting clean hydrogen energy, but detrimental chlorine species (i.e., chloride and hypochlorite) cause severe corrosion at the anode. Here, we report our recent finding that benzoate anions-intercalated NiFe-layered double hydroxide nanosheet on carbon cloth (BZ-NiFe-LDH/CC) behaves as a highly efficient and durable monolithic catalyst for alkaline seawater oxidation, affords enlarged interlayer spacing of LDH, inhibits chlorine (electro)chemistry, and alleviates local pH drop of the electrode. It only needs an overpotential of 320 mV to reach a current density of 500 mA·cm^–2 in 1 M KOH. In contrast to the fast activity decay of NiFe-LDH/CC counterpart during long-term electrolysis, BZ-NiFe-LDH/CC achieves stable 100-h electrolysis at an industrial-level current density of 500 mA·cm^–2 in alkaline seawater. Operando Raman spectroscopy studies further identify structural changes of disordered δ (Ni^III-O) during the seawater oxidation process.

Seawater electrolysis is the most promising technology for large scale hydrogen production due to the abundance and low cost of seawater in nature. However, compared with the traditional freshwater electrolysis, the issues of electrode poisoning and corrosion will occur during the seawater electrolysis process, and active and stable electrocatalysts for the hydrogen evolution reaction (HER) are thus highly desired. In this work, N, O-doped carbon foam in-situ derived from commercial melamine foam is proposed as a high-active metal-free HER electrocatalyst for seawater splitting. In acidic seawater, our catalyst shows high hydrogen generation performance with small overpotential of 161 mV at 10 mA·cm⁻², a low Tafel slop of 97.5 mV·dec⁻¹, and outstanding stability.