Dynamic chloride ion adsorption on single iridium atom boosts seawater oxidation catalysis.

Seawater electrolysis offers a renewable, scalable, and economic means for green hydrogen production. However, anode corrosion by Cl- pose great challenges for its commercialization. Herein, different from conventional catalysts designed to repel Cl- adsorption, we develop an atomic Ir catalyst on cobalt iron layered double hydroxide (Ir/CoFe-LDH) to tailor Cl- adsorption and modulate the electronic structure of the Ir active center, thereby establishing a unique Ir-OH/Cl coordination for alkaline seawater electrolysis. Operando characterizations and theoretical calculations unveil the pivotal role of this coordination state to lower OER activation energy by a factor of 1.93. The Ir/CoFe-LDH exhibits a remarkable oxygen evolution reaction activity (202 mV overpotential and TOF = 7.46 O2 s-1) in 6 M NaOH+2.8 M NaCl, superior over Cl--free 6 M NaOH electrolyte (236 mV overpotential and TOF = 1.05 O2 s-1), with 100% catalytic selectivity and stability at high current densities (400-800 mA cm-2) for more than 1,000 h.

Polar Aromatic Two-dimensional Dion-Jacobson Halide Perovskites for Efficient Photocatalytic H2 Evolution.

Polar materials with spontaneous polarization (Ps) have emerged as highly promising photocatalysts for efficient photocatalytic H2 evolution owing to the Ps-enhanced photogenerated carrier separation. However, traditional inorganic polar materials often suffer from limitations such as wide band gaps and poor carrier transport, which hinders their photocatalytic H2 evolution efficiency. Here, we rationally synthesized a series of isostructural two-dimensional (2D) aromatic Dion-Jacobson (DJ) perovskites, namely (2-(2-Aminoethyl)pyridinium)PbI4 (2-APDPI), (3-(2-Aminoethyl)pyridinium)PbI4 (3-APDPI), and (4-(2-Aminoethyl)pyridinium)PbI4 (4-APDPI), where 2-APDPI and 4-APDPI crystalize in polar space groups with piezoelectric constants (d33) of approximately 40 pm V-1 and 3-APDPI adopts a centrosymmetric structure. Strikingly, owing to the Ps-facilitated separation of photogenerated carriers, polar 2-APDPI and 4-APDPI exhibit a 3.9- and 2.8-fold increase, respectively, in photocatalytic H2 evolution compared to the centrosymmetric 3-APDPI. As a pioneering study, this work provides an efficient approach for exploring new polar photocatalysts and highlights their potential in promoting photocatalytic H2 evolution.

Dynamic coordination engineering of 2D PhenPtCl2 nanosheets for superior hydrogen evolution.

Exploring the dynamic structural evolution of electrocatalysts during reactions represents a fundamental objective in the realm of electrocatalytic mechanism research. In pursuit of this objective, we synthesized PhenPtCl2 nanosheets, revealing a N2-Pt-Cl2 coordination structure through various characterization techniques. Remarkably, the electrocatalytic performance of these PhenPtCl2 nanosheets for hydrogen evolution reaction (HER) surpasses that of the commercial Pt/C catalyst across the entire pH range. Furthermore, our discovery of the dynamic coordination changes occurring in the N2-Pt-Cl2 active sites during the electrocatalytic process, as clarified through in situ Raman and X-ray photoelectron spectroscopy, is particularly noteworthy. These changes transition from Phen-Pt-Cl2 to Phen-Pt-Cl and ultimately to Phen-Pt. The Phen-Pt intermediate plays a pivotal role in the electrocatalytic HER, dynamically coordinating with Cl- ions in the electrolyte. Additionally, the unsaturated, two-coordinated Pt within Phen-Pt provides additional space and electrons to enhance both H+ adsorption and H2 evolution. This research illuminates the intricate dynamic coordination evolution and structural adaptability of PhenPtCl2 nanosheets, firmly establishing them as a promising candidate for efficient and tunable electrocatalysts.

Atomic-level polarization in electric fields of defects for electrocatalysis.

The thriving field of atomic defect engineering towards advanced electrocatalysis relies on the critical role of electric field polarization at the atomic scale. While this is proposed theoretically, the spatial configuration, orientation, and correlation with specific catalytic properties of materials are yet to be understood. Here, by targeting monolayer MoS2 rich in atomic defects, we pioneer the direct visualization of electric field polarization of such atomic defects by combining advanced electron microscopy with differential phase contrast technology. It is revealed that the asymmetric charge distribution caused by the polarization facilitates the adsorption of H*, which originally activates the atomic defect sites for catalytic hydrogen evolution reaction (HER). Then, it has been experimentally proven that atomic-level polarization in electric fields can enhance catalytic HER activity. This work bridges the long-existing gap between the atomic defects and advanced electrocatalysis by directly revealing the angstrom-scale electric field polarization and correlating it with the as-tuned catalytic properties of materials; the methodology proposed here could also inspire future studies focusing on catalytic mechanism understanding and structure-property-performance relationship.

Frenkel-defected monolayer MoS2 catalysts for efficient hydrogen evolution.

Defect engineering is an effective strategy to improve the activity of two-dimensional molybdenum disulfide base planes toward electrocatalytic hydrogen evolution reaction. Here, we report a Frenkel-defected monolayer MoS2 catalyst, in which a fraction of Mo atoms in MoS2 spontaneously leave their places in the lattice, creating vacancies and becoming interstitials by lodging in nearby locations. Unique charge distributions are introduced in the MoS2 surface planes, and those interstitial Mo atoms are more conducive to H adsorption, thus greatly promoting the HER activity of monolayer MoS2 base planes. At the current density of 10 mA cm-2, the optimal Frenkel-defected monolayer MoS2 exhibits a lower overpotential (164 mV) than either pristine monolayer MoS2 surface plane (358 mV) or Pt-single-atom doped MoS2 (211 mV). This work provides insights into the structure-property relationship of point-defected MoS2 and highlights the advantages of Frenkel defects in tuning the catalytic performance of MoS2 materials.

Regenerated and rotation-induced cellulose-wrapped oriented CNT fibers for wearable multifunctional sensors.

Recently, wearable multifunctional fibers have attracted widespread attention due to their applications in wearable smart textiles. However, stable application, large-scale production and more functions are still the greatest challenges for functional fiber devices. In this study, wearable multi-functional coaxial fibers with oriented carbon nanotubes (CNTs) were achieved for the first time coaxial wet-spinning with rotating coagulation bath. Specifically, the cellulose solution can be regenerated in the coagulation bath and the CNTs dispersion will be oriented under the rotating force. The synergy between hydrogen bonding and van der Waals interaction enhance the mechanical strength of coaxial fibers. Especially, CNTs can prevent the rotation of the cellulose chain and the bending of the glycosidic twist angle at the atomic scale as indicated by molecular dynamics (MD) simulations. When the fibers are strained, the cellulose sheath will drive the movement of CNTs, causing changes involving the effective contact area and number of conductive paths. Therefore, the high electrical resistance response change enables the as-obtained coaxial fibers to exhibit a great potential in wearable strain sensors. Furthermore, coaxial fibers can be made into electric heaters based on the Joule heating principle. The heating temperature reaches more than 160 °C within 6 s at 10 V, which is of a great value for large area flexible heaters. Besides, the coaxial fibers can further be used as temperature-sensitive devices to accurately perceive the external temperature. Therefore, the scalable synthesis of multifunctional coaxial fibers is significantly expected to provide a platform for the large-scale production of multifunctional wearable intelligent textiles.

Interface Modulating CNTs@PANi Hybrids by Controlled Unzipping of the Walls of CNTs To Achieve Tunable High-Performance Microwave Absorption.

Making full use of the interface modulation-induced interface polarization is an effective strategy to achieve excellent microwave absorption (MA). In this study, we develop an interfacial modulation strategy for achieving this goal in the commonly reported dielectric carbon nanotubes@polyaniline (CNTs@PANi) hybrid microwave absorber by optimizing the CNT nanocore structure. The heterogeneous interfaces from PANi and CNTs can be well regulated by longitudinal unzipping of the walls of CNTs to form 1D CNT- and 3D CNT-bridged graphene nanoribbons and 2D graphene nanoribbons. By controlling the oxidation peeling degree of CNTs, their interface area and defects are enhanced, thus producing more polarization centers to generate interfacial polarization and polarization relaxation, and also introducing more PANi loadings. Furthermore, more interface contact area can be produced between CNTs and PANi. This could induce a strong dielectric resonant and further improve the impedance matching, leading to significant enhancement of MA performance. With filler loading of only 10 wt % and a thinner coating thickness of 2.4 mm, the optimized CNTs@PANi exhibits excellent MA performance with the minimum reflection loss (RLmin) value of -45.7 dB at 12.0 GHz and the effective bandwidth is from 10.2 to 14.8 GHz. Meanwhile, the broadest effective bandwidth reaches 5.6 GHz, covering the range of 12.4-18.0 GHz with a thin thickness of 2.0 mm and its RLmin reaches -29.0 dB at 14.6 GHz. It is believed that the proposed interfacial modulation strategy can provide new opportunities for designing efficient MA absorbers.