Recent advances of H-intercalated Pd-based nanocatalysts for electrocatalytic reactions

The intercalation of H into Pd-based nanocatalysts plays a crucial role in optimizing the catalytic performance by tailoring the structural and electronic properties. We herein present a comprehensive review about the recent progress of interstitial hydrogen atom modified Pd-based nanocatalysts for various energy-related electrocatalytic reactions. Before systematically manifesting the great potential of Pd-based hydrides for electrocatalytic applications, we have briefly illustrated the synthesis strategies and corresponding mechanisms for the Pd-based hydrides. This is followed by a comprehensive discussion about the fundamentals and functions of H intercalation in tailoring their physicochemical and electrochemical properties. Subsequently, we focus on the widespread application of Pd-based hydrides for electrocatalytic reactions, with the emphasis on the role of H intercalation played in determining electrocatalytic performance. Finally, the future direction and perspectives regarding the development of more efficient Pd-based hydrides are also manifested.

Interfacial built-in electric-field for boosting energy conversion electrocatalysis

The formation of a built-in electric field (BIEF) can induce electron-rich and electron-poor counterparts to synergistically modify electronic configurations and optimize the binding strengths with intermediates, thereby leading to outstanding electrocatalytic performance. Herein, a critical review regarding the concept, modulation strategies, and applications of BIEFs is comprehensively summarized, which begins with the fundamental concepts, together with the advantages of BIEF for boosting electrocatalytic reactions. Then, a systematic summary of the advanced strategies for the modulation of BIEF along with the in-detail mechanisms in its formation are also added. Finally, the applications of BIEF in driving electrocatalytic reactions and some cascade systems for illustrating the conclusive role from the induced BIEF are also systematically discussed, followed by perspectives on the future deployment and opportunity of the BIEF design.

Two-dimensional template-directed synthesis of one-dimensional kink-rich Pd3Pb nanowires for efficient oxygen reduction

Developing facile synthetic strategies toward ultrafine one-dimensional (1D) nanowires (NWs) with rich catalytic hot spots is pivotal for exploring effective heterogeneous catalysts. Herein, we demonstrate a two-dimensional (2D) template-directed strategy for synthesizing 1D kink-rich Pd₃Pb NWs with abundant grain boundaries to serve as high-efficiency electrocatalysts toward oxygen reduction reaction (ORR). In this one-pot synthesis, ultrathin Pd nanosheets were initially generated, which then served as self-sacrificial 2D nano-templates. A dynamic equilibrium growth was subsequently established on the 2D Pd nanosheets through the center-selected etching of Pd atoms and edge-preferred co-deposition of Pd/Pb atoms. This was followed by the oriented attachment of the generated Pd/Pb alloy nanograins and fragments. Thus, kink-rich Pd₃Pb NWs with rich grain boundary defects were obtained in high yield, and these NWs were used as electrocatalytic active catalysts. The surface electronic interaction between Pd and Pb atoms effectively decreased the surface d-band center to weaken the binding of oxygen-containing intermediates toward improved ORR kinetics. Specifically, the kink-rich Pd₃Pb NWs/C catalyst delivered outstanding ORR mass activity and specific activity (2.26 A⋅mg_Pd^-1 and 2.59 mA⋅cm^-2, respectively) in an alkaline solution. These values were respectively 13.3 and 10.8 times those of state-of-the-art commercial Pt/C catalyst. This study provides an innovative strategy for fabricating defect-rich low-dimensional nanocatalysts for efficient energy conversion catalysis.

Synthesis of unconventional Pd-Se nanoparticles for phase-dependent ethanol electrooxidation

By tuning the amount of the Se precursors during the synthesis, orthorhombic PdSe₂, cubic Pd₁₇Se₁₅, and monoclinic Pd₇Se₂ nanoparticles are synthesized, which show phase-dependent electrocatalysis for the ethanol oxidation reaction. This work advances the controllable synthesis of transition metal selenides and inspires their applications in electrocatalysis.

Intensifying Hydrogen Spillover for Boosting Electrocatalytic Hydrogen Evolution Reaction

Hydrogen spillover has attracted increasing interests in the field of electrocatalytic hydrogen evolution reaction (HER) in recent years because of their distinct reaction mechanism and beneficial terms for simultaneously weakening the strong hydrogen adsorption on metal and strengthening the weak hydrogen adsorption on support. By taking advantageous merits of efficient hydrogen transfer, hydrogen spillover-based binary catalysts have been widely investigated, which paves a new way for boosting the development of hydrogen production by water electrolysis. In this paper, we summarize the recent progress of this interesting field by focusing on the advanced strategies for intensifying the hydrogen spillover towards HER. In addition, the challenging issues and some perspective insights in the future development of hydrogen spillover-based electrocatalysts are also systematically discussed.

Strategies for Promoting Catalytic Performance of Ru-based Electrocatalysts towards Oxygen/Hydrogen Evolution Reaction

Ru-based materials hold great promise for substituting Pt as potential electrocatalysts toward water electrolysis. Significant progress is made in the fabrication of advanced Ru-based electrocatalysts, but an in-depth understanding of the engineering methods and induced effects is still in their early stage. Herein, we organize a review that focusing on the engineering strategies toward the substantial improvement in electrocatalytic OER and HER performance of Ru-based catalysts, including geometric structure, interface, phase, electronic structure, size, and multicomponent engineering. Subsequently, the induced enhancement in catalytic performance by these engineering strategies are also elucidated. Furthermore, some representative Ru-based electrocatalysts for the electrocatalytic HER and OER applications are also well presented. Finally, the challenges and prospects are also elaborated for the future synthesis of more effective Ru-based catalysts and boost their future application.

Dimension Engineering in Noble-Metal-Based Electrocatalysts for Water Splitting

Dimension engineering plays a critical role in determining the electrocatalytic performance of catalysts towards water electrolysis since it is highly sensitive to the surface and interface properties. Bearing these considerations into mind, intensive efforts have been devoted to the rational dimension design and engineering, and many advanced nanocatalysts with multidimensions have been successfully fabricated. Aiming to provide more guidance for the fabrication of highly efficient noble-metal-based electrocatalysts, this review has focused on the recent progress in dimension engineering of noble-metal-based electrocatalysts towards water splitting, including the advanced engineering strategies, the application of noble-metal-based electrocatalysts with distinctive geometric structure from 0D to 1D, 2D, 3D, and multidimensions. In addition, the perspective insights and challenges of the dimension engineering in the noble-metal-based electrocatalysts is also systematically discussed.

Hollow Heterostructured Nanocatalysts for Boosting Electrocatalytic Water Splitting

The implementation of electrochemical water splitting demands the development and application of electrocatalysts to overcome sluggish reaction kinetics of hydrogen/oxygen evolution reaction (HER/OER). Hollow nanostructures, particularly for hollow heterostructured nanomaterials can provide multiple solutions to accelerate the HER/OER kinetics owing to their advantageous merit. Herein, the recent advances of hollow heterostructured nanocatalysts and their excellent performance for water splitting are systematically summarized. Starting by illustrating the intrinsically advantageous features of hollow heterostructures, achievements in engineering hollow heterostructured electrocatalysts are also highlighted with the focus on structural design, interfacial engineering, composition regulation, and catalytic evaluation. Finally, some perspective insights and future challenges of hollow heterostructured nanocatalysts for electrocatalytic water splitting are also discussed.

Pd-Based Metallenes for Fuel Cell Reactions

Pd-based metallenes, atomically thin layers composed primarily of under-coordinated Pd atoms, have emerged as the newest members in the family of two-dimensional (2D) nanomaterials. Moreover, the unique physiochemical properties, high intrinsic activity associated with metallenes coupled with the ease of applying chemical modifications result in great potential in catalyst engineering for fuel cell reactions. Especially in recent years, interest in Pd-based metallenes is growing, as evidenced by surge in available literatures. Herein, we have reviewed the recent findings achieved in Pd-based metallenes in fuel cells by highlighting the technologies available for deriving metallenes and manifesting the modification strategies for designing them to better suit the application demand. Moreover, we also discuss the perspective insights of Pd-based metallenes for fuel cells regarding the surfactant-free synthesis method, strain engineering, constructing high-entropy alloy, and so on.

Coupling Transition Metal Compound with Single-Atom Site for Water Splitting Electrocatalysis

Single-atom site catalysts (SACs) provide an ideal platform to identify the active centers, explore the catalytic mechanism, and establish the structure-property relationships, and thus have attracted increasing interests for electrocatalytic energy conversion. Substantial endeavors have been devoted to the construction of carbon-supported SACs, and their progress have been comprehensively reviewed. Compared with carbon-supported SACs, transition metal compounds (TMCs)-supported SACs are still in their infancy in the field of electrocatalysis. However, they have also aroused ever-increasing attention for driving electrocatalytic water splitting, and emerged as an indispensable class of SACs in recent years, predominately owing to their inherently structural features, such as rich anchoring sites, surface defects, and lattice vacancy. Herein, in this review, we have systematically summarized the recent advances of a variety of TMC supported SACs toward electrocatalytic water splitting. The advanced characterization techniques and theoretical analyses for identifying and monitoring the atomic structure of SACs are firstly manifested. Subsequently, the anchoring and stabilization mechanisms for TMC supported SACs are also highlighted. Thereafter, the advances of TMC supported SACs for driving water electrolysis are systematically unraveled.

Plasmon-Mediated Oxidase-like Activity on Ag@ZnS Heterostructured Hollow Nanowires for Rapid Visual Detection of Nitrite

Rational design of fast and sensitive determination of nitrite (NO₂^-) from a complicated actual sample overtakes a crucial role in constructing a high-efficiency sensing platform. Herein, a visual NO₂^- sensing platform with outstanding selectivity, sensitivity, and stability based on a surface plasmon resonance (SPR)-enhanced oxidase-like activity has been proposed. Benefiting from the intrinsic photocatalytic activity and limited light penetration of ZnS, the oxidase-like activity based on ZnS decorated on Ag nanowires (Ag@ZnS) is determined. It is demonstrated that the electrons are generated efficiently on the surface of ZnS and then transferred into the hot electrons of Ag with the help of localized SPR excitation, thus greatly oxidating the colorless 3,3',5,5'-tetramethylbenzidine (TMB) to produce dark blue oxidized TMB (oxTMB). When nitrite is added into the reaction system, the oxTMB will selectively react with NO₂^- to generate diazotized oxTMB, leading to a visual color change from dark blue to light green and subsequently to dark yellow. Owing to the specific recognition between nitrite and oxTMB, the recovery of catalytic activity induced an enhanced colorimetric test with a wider linear range for NO₂^- determination, an ultralow detection limit of 0.1 μM, excellent selectivity, and practicability for application in real samples. This plasmon-enhanced oxidase-like activity not only provides a smart approach to realize a colorimetric assay with high sensitivity and simplicity but also modulates oxidase-like activities.

Introducing Te for boosting electrocatalytic reactions

The deployment of robust catalysts for electrochemical reactions is a critical topic for energy conversion techniques. Te-based nanomaterials have attracted increasing attention for their application in electrochemical reactions due to their positive influence on the electrocatalytic performance induced by their distinctive electronic and physicochemical properties. Herein, we have summarized the recent progress on Te-based nanocatalysts for electrocatalytic reactions by primarily focusing on the positive influence of Te on electrocatalysts. Firstly, Te-based nanomaterials can serve as an ideal template for the construction of well-defined nanostructures. Secondly, Te doping can significantly modify the electronic structure of the host catalyst, thereby, leading to the optimization of binding strength with intermediates. Furthermore, the Te etching strategy can also create a high density of surface defects, thereby leading to substantial improvement in the electrocatalytic performance. Additionally, many representative Te-based nanocatalysts for electrocatalytic reactions are also summarized and systematically discussed. Finally, a conclusive and perspective discussion is also provided to provide guidance for the future development of more efficient electrocatalysts.

Mo doping and Se vacancy engineering for boosting electrocatalytic water oxidation by regulating the electronic structure of self-supported Co9Se8@NiSe

Oxygen evolution reactions (OERs) are regarded as the rate-determining step of electrocatalytic overall water splitting, which endow OER electrocatalysts with the advantages of high activity, low cost, good conductivity, and excellent stability. Herein, a facile H₂O₂-assisted etching method is proposed for the fabrication of Mo-doped ultrathin Co₉Se₈@NiSe/NF-X heterojunctions with rich Se vacancies to boost electrocatalytic water oxidation. After step-by-step electronic structure modulation by Mo doping and Se vacancy engineering, the self-standing Mo-Co₉Se₈@NiSe/NF-60 heterojunctions deliver a current density of 50 mA cm^-2 with an overpotential of 343 mV and a cell voltage of only 1.87 V at 50 mA cm^-2 for overall water splitting in 1.0 M KOH. Our study opens up the possibility of realizing step-by-step electronic structure modulation of nonprecious OER electrocatalysts via heteroatom doping and vacancy engineering.

Heterojunction MnO2-nanosheet-decorated Ag nanowires with enhanced oxidase-like activity for the sensitive dual-mode detection of glutathione

The biocatalytic design of nanomaterials with enzyme-like activity is considered a reliable and promising toolkit for the generation of diagnostic agents in complex biological microenvironments. However, the preparation of nanomaterials while maintaining a high catalytic activity in tumor cells (pH 6.0-6.5) poses a prominent challenge. Herein, we constructed a biomimetic enzyme-trigged dual-mode system with colorimetry at 652 nm and photothermal biosensors to detect glutathione based on hollow MnO₂-nanosheet-decorated Ag nanowires (Ag@MnO₂) as an oxidase-like nanozyme. As expected, Ag@MnO₂ catalyzed the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) in the absence of H₂O₂, leading to a blue-colored oxidized TMB (oxTMB) that displayed oxidase-like activity in pH 6.0. Interestingly, the portable dual-mode colorimetry and photothermal method for GSH was developed based on the redox reaction between GSH and oxTMB. This detection method exhibited a wide linear range of 0.1-55 μM for GSH with a low detection limit of 0.08 μM. This work highlights a new insight into nanotechnology by taking advantage of biomimetic design in biological analysis.

Cation-Anion Dual Doping Modifying Electronic Structure of Hollow CoP Nanoboxes for Enhanced Water Oxidation Electrocatalysis

Tuning the electronic state of a nanocatalyst is of vital importance for elevating its catalytic performance toward oxygen evolution reaction (OER). Herein, a cation-anion dual doping strategy has been proposed for modifying the electronic structure of CoP via doping Fe and S atoms. Impressively, Fe doping has been demonstrated to be favorable for improving the carrier density of CoP to produce more hydroxyl radicals (^•OH), while S doping can further modify the electronic structure of CoP to improve the charge-transfer characteristics, thereby synergistically decreasing the energy barrier for the transformation of O* to OOH* and promoting the electrocatalytic OER performance. More importantly, the highly open nanobox structure is also beneficial for the exposure of more accessible catalytically active sites, which can substantially facilitate the electron and mass transport, leading to the superb catalytic OER performance. The successful modulation of OER performance via dual-doping strategy will pose a new strategy for designing more advanced nanocatalysts for energy-related catalysis process.

Biosynthesis-mediated Ni-Fe-Cu LDH-to-sulfides transformation enabling sensitive detection of endogenous hydrogen sulfide with dual-readout signals

Hydrogen sulfide (H₂S) is a vital endogenous gas signal molecule undertaking numerous physiological functions such as biological regulation and cytoprotection. Herein, we developed an electrochemical (EC) and photothermal (PT) dual-readout signals method for H₂S detection based on a novel biosynthesis-mediated Ni-Fe-Cu LDH-to-sulfides transformation strategy. Interestingly, the Cu²⁺-based Ni-Fe LDH (Ni-Fe-Cu LDH) can act as the Cu²⁺ source to react with H₂S, resulting in the in-situ generation of Cu_xS on Ni-Fe-Cu LDH surfaces. Because of the EC signal and intrinsic near-infrared (NIR) PT conversion ability of Cu_xS under 808 nm laser irradiation, the obtained Cu_xS@Ni-Fe-Cu LDH is applied to stimulate EC signal and temperature readout. By this means, a dual-readout signal mode is established for H₂S detection. Under the optimum conditions, this combination of EC and PT methods displays a wide linear range for H₂S to 0.1 μM-90 μM and 50 μM-400 μM, respectively, with a low detection limit of 0.09 μM. In addition, the practicality of Ni-Fe-Cu LDH is verified by determination of endogenous H₂S in living cells. This work not only provides a promising application for H₂S diagnosis but also exhibits the new characteristic of Ni-Fe-Cu LDH nanomaterials as signal transduction tags.

Recent advances in hollow nanomaterials with multiple dimensions for electrocatalytic water splitting

Electrocatalytic water splitting has great research prospects in the production of green hydrogen energy, and electrocatalysts are the prerequisite. As widely employed efficient electrocatalysts, hollow nanostructures have attracted a lot of research attention due to their excellent catalytic activity and structural stability. Moreover, the abundant catalytically active sites and tunable morphology also make hollow nanomaterials promising electrocatalysts for water splitting. Despite these advantages, the industrial applications of these hollow nanocatalysts are impeded by limitations like the lack of effective synthesis methods and unclear formation mechanisms. Therefore, extensive efforts have been devoted to the development of efficient synthesis strategies to boost the development of more efficient hollow electrocatalysts, and great progress has been achieved in recent years. To gain a better understanding of the rapid development of hollow nanocatalysts for water splitting, we herein organize a review to summarize the recent synthetic methods and advantages of hollow materials with different dimensions. The specific advantages of hollow nanomaterials in electrocatalytic water splitting, such as abundant active sites, a stable structure, high mass transfer efficiency, and reduced aggregation of catalytic particles, are also summarized. Finally, the challenges and prospects of hollow nanostructures with multiple dimensions in electrocatalytic water splitting are further explored.

Hierarchical Hollow CoWO4-Co(OH)2 Heterostructured Nanoboxes Enabling Efficient Water Oxidation Electrocatalysis

Rational design and construction of well-defined hollow heterostructured nanomaterials assembled by ultrathin nanosheets overtakes crucial role in developing high-efficiency oxygen evolution reaction (OER) electrocatalysts. Herein, a reliable metal-organic framework-mediated and cation-exchange strategy to tune the geometric structure and multicomponent heterostructures has been proposed for the fabrication of hollow CoWO₄-Co(OH)₂ hierarchical nanoboxes assembled by rich ultrathin nanosheets. Benefiting from the hierarchical hollow nanostructure, the CoWO₄-Co(OH)₂ nanoboxes offer plenty of metal active centers available for reaction intermediates. Moreover, the well-defined nanointerfaces between CoWO₄ and Co(OH)₂ can function as the bridge for boosting the efficient electron transfer from CoWO₄ to Co(OH)₂. As a consequence, the optimized CoWO₄-Co(OH)₂ nanoboxes can exhibit outstanding electrocatalytic performance toward OER by delivering 10 mA cm^-2 with a low overpotential of 280 mV and a small Tafel slope of 70.6 mV dec^-1 as well as outstanding electrochemical stability. More importantly, this CoWO₄-Co(OH)₂ heterostructured nanocatalyst can couple with Pt/C to drive overall water splitting to achieve 10 mA cm^-2 with a voltage of 1.57 V.

Bioinspired silk fibroin materials: From silk building blocks extraction and reconstruction to advanced biomedical applications

Silk fibroin has become a promising biomaterial owing to its remarkable mechanical property, biocompatibility, biodegradability, and sufficient supply. However, it is difficult to directly construct materials with other formats except for yarn, fabric and nonwoven based on natural silk. A promising bioinspired strategy is firstly extracting desired building blocks of silk, then reconstructing them into functional regenerated silk fibroin (RSF) materials with controllable formats and structures. This strategy could give it excellent processability and modifiability, thus well meet the diversified needs in biomedical applications. Recently, to engineer RSF materials with properties similar to or beyond the hierarchical structured natural silk, novel extraction and reconstruction strategies have been developed. In this review, we seek to describe varied building blocks of silk at different levels used in biomedical field and their effective extraction and reconstruction strategies. This review also present recent discoveries and research progresses on how these functional RSF biomaterials used in advanced biomedical applications, especially in the fields of cell-material interactions, soft tissue regeneration, and flexible bioelectronic devices. Finally, potential study and application for future opportunities, and current challenges for these bioinspired strategies and corresponding usage were also comprehensively discussed. In this way, it aims to provide valuable references for the design and modification of novel silk biomaterials, and further promote the high-quality-utilization of silk or other biopolymers.

Electrospun one-dimensional electrocatalysts for boosting electrocatalysis

Electrocatalytic reaction plays a crucial role in determining the energy conversion efficiency in advanced technology. However, it is limited by the sluggish reaction kinetics and high energy barrier. These shortcomings...