ZIF-67-Derived (NiCo)S2@NC Nanosheet Arrays Hybrid for Efficient Overall Water Splitting

Unique sandwich-cookie-like nanosheet array heterojunction bifunctional electrocatalyst towards efficient overall water/seawater splitting

Construction of multi-component heterostructures is an effective strategy for electrocatalysts to improve both the hydrogen evolution reaction (HER) at the cathode and the oxygen evolution reaction (OER) activity at the anode. Herein, an efficient bifunctional electrocatalyst towards overall water/seawater splitting (OW/SS) is reported with strategy of heterostructure construction (ruthenium/nickel phosphorus) on nickel hydroxide (Ni(OH)2). With the unique hydrolysis layer (Ni(OH)2), the processes of H2O hydrolysis and the adsorption/desorption of H*/O-containing intermediates (OH, O, OOH) were greatly boosted by Ru and P sites, which acted as the catalytic active centers of OER and HER, respectively. In addition, the electronic structure reconfiguration was realized through the strong interaction between multi-interfaces. For alkaline HER at the current density of 10 mA cm-2, the overpotential of Ru-P-Ni(OH)2/NF (denoted as RNPOH/NF) was 98 mV, whereas just 230 mV of overpotential was essential to stimulate alkaline OER at the current density of 20 mA cm-2. Specifically, as a bifunctional electrocatalyst towards overall water splitting, RNPOH/NF deserves cell voltages of 1.7/1.92 V and 1.75/1.94 V, respectively, to activate current densities of 50/100 mA cm-2 in alkaline water/seawater systems, together with a good durability of 12 h. This work contributes insights to the development of bifunctional electrocatalysts for overall water/seawater splitting.

Synthesis and Electrocatalytic Applications of Layer-Structured Metal Chalcogenides Composites

Featured with the attractive properties such as large surface area, unique atomic layer thickness, excellent electronic conductivity, and superior catalytic activity, layered metal chalcogenides (LMCs) have received considerable research attention in electrocatalytic applications. In this review, the approaches developed to synthesize LMCs-based electrocatalysts are summarized. Recent progress in LMCs-based composites for electrochemical energy conversion applications including oxygen reduction reaction, carbon dioxide reduction reaction, oxygen evolution reaction, hydrogen evolution reaction, overall water splitting, and nitrogen reduction reaction is reviewed, and the potential opportunities and practical obstacles for the development of LMCs-based composites as high-performing active substances for electrocatalytic applications are also discussed. This review may provide an inspiring guidance for developing high-performance LMCs for electrochemical energy conversion applications.

Integrated Heterogeneous Engineering with the Vacancy Defect of Porous CoPv-MoxPv Nanosheets for an Accelerated Hydrogen Evolution Reaction

Electrochemical water splitting is a possible way of realizing sustainable and clean hydrogen production but is challenging, because a highly active and durable electrocatalyst is essential. In this work, we integrated heterogeneous engineering and vacancy defect strategies to design and fabricate a heterostructure electrocatalyst (CoPv-MoxPv/CNT) with abundant phosphorus vacancies attached to carbon nanotubes (CNTs). The vacancy defects enabled the optimization of the electronic structure; thereby, the electron-rich low-valent metal sites enhanced the ability of nonmetallic P to capture proton H. Meanwhile, the heterogeneous interface between bimetallic phosphides and CNTs realized rapid electron transfer. In addition, the Co, Mo, and P active species in the electrocatalytic process exposed increased amounts of active sites featuring porous nanosheet structures, which facilitated the adsorption of reaction intermediates and thus enhanced the hydrogen evolution reaction performance. In particular, the optimized CoPv-MoxPv/CNT catalyst possesses an overpotential of 138 mV at a current density of 10 mA cm-2 and long-term stability for 24 h. This work offers insights and possibilities for the engineering and exploration of transition metal-based electrocatalysts through combining multiple synergistic strategies.

Metal-Organic Framework (MOF)-Based Clean Energy Conversion: Recent Advances in Unlocking its Underlying Mechanisms

Carbon neutrality is an important goal for humanity . As an eco-friendly technology, electrocatalytic clean energy conversion technology has emerged in the 21st century. Currently, metal-organic framework (MOF)-based electrocatalysis, including oxygen reduction reaction (ORR), oxygen evolution reaction (OER), hydrogen evolution reaction (HER), hydrogen oxidation reaction (HOR), carbon dioxide reduction reaction (CO2RR), nitrogen reduction reaction (NRR), are the mainstream energy catalytic reactions, which are driven by electrocatalysis. In this paper, the current advanced characterizations for the analyses of MOF-based electrocatalytic energy reactions have been described in details, such as density function theory (DFT), machine learning, operando/in situ characterization, which provide in-depth analyses of the reaction mechanisms related to the above reactions reported in the past years. The practical applications that have been developed for some of the responses that are of application values, such as fuel cells, metal-air batteries, and water splitting have also been demonstrated. This paper aims to maximize the potential of MOF-based electrocatalysts in the field of energy catalysis, and to shed light on the development of current intense energy situations.

Benzene-fused porphyrin(2.1.2.1) array: synthesis, structure, and electrocatalytic hydrogen evolution

The development of efficient molecular catalysts for the electrocatalytic hydrogen evolution reaction (HER) is very necessary and important for fuel cells. In this work, we report a new benzene-fused porphyrin(2.1.2.1) array, BPD, with a unique S-shaped molecular conformation. The electrochemistry of BPD displays multielectron donating and accepting properties owing to the two porphyrin(2.1.2.1) blocks and degenerate molecular orbitals. The electrocatalytic HER activity of BPD is remarkably higher-that is, BPD exhibited lower overpotential, faster HER kinetics, faster charge transfer kinetics, and extended catalytic stability-than that of the porphyrin(2.1.2.1) copper complex monomer.

Synergistic Interfacial Engineering of Heterostructured Cobalt Phosphide Spheres/Cobalt Hydroxide Nanosheets for Overall Water Splitting

Recently, transition metal phosphides (TMPs) have been widely explored for the hydrogen evolution reaction (HER) due to their advantaged activity. Nevertheless, the OER performance of TMPs in an alkaline medium is still unsatisfactory. Therefore, interfacial engineering of TMPs to enhance the OER performance is highly desirable. Herein, a Co(OH)2 nanosheet coupled with a CoP sphere supported on nickel foam (NF) is developed by a simple two-step electrodeposition. The large surface area derived from stacked nanosheets and the electronic regulation induced by heterostructure can significantly enhance charge/mass transfer and expose more active sites, thus accelerating the kinetics of the reaction. In addition, the strong electronic interaction between CoP and Co(OH)2 is conducive to the generation of a high valence cobalt center; thus, the electrocatalytic performances toward HER and OER are remarkably improved. Impressively, the optimized CoP/Co(OH)2@NF heterostructure obtains an excellent HER and OER performance with low overpotentials of 76 and 266 mV at 10 mA cm-2, respectively, superior to the commercial Pt/C and RuO2. Moreover, the optimized CoP/Co(OH)2@NF can afford the lowest cell voltage of 1.58 V to achieve 10 mA cm-2 for alkaline overall water splitting and shows outstanding long-term stability.

Antibacterial and antibiofilm activities of ZIF-67

Currently, antibiotic-resistant bacteria represent a serious threat to public health worldwide. Biofilm formation potentiates both virulence and antibiotic resistance of bacteria. Therefore, the discovery of new antibacterial and antibiofilm compounds is an issue of paramount importance to combat and prevent hard-to-treat bacterial infections. Zeolitic-imidazolate-frameworks (ZIFs) are metallo-organic compounds known to have various interesting chemical and biological applications, including antibacterial properties. In this study, we synthesized ZIF-67 nanoparticles, formed by imidazolate anions and cobalt cations, and found that they inhibit the growth of Acinetobacter baumannii, Pseudomonas aeruginosa, and Staphylococcus aureus. Sub-inhibitory concentrations of ZIF-67 were also able to significantly reduce the biomass of pre-established biofilms of these pathogenic bacteria. On the other hand, the ZIF-67 nanoparticles had null or low cytotoxicity in mammalian cells at those concentrations showing antibacterial or antibiofilm activities. Thus, our results reveal the potential of ZIF-67 nanoparticles to be used against pathogenic bacteria.

Engineering multilayer catalytic interfaces with N, S co-regulation for high performance water splitting

The rational design of hierarchical nano-heterojunction electrocatalysts with efficient and durable water splitting performance is a hot research topic in the field of sustainable energy conversion. Herein, chemical vapor deposition methods are exploited to dope N and S elements in a core-shell structured Co₃O₄@NiMoO₄ with a layered structure (N, S-Co₃O₄@NiMoO₄/NF₄₀₀). The close contact between Co₃O₄ nanowires and N, S co-doped NiMoO₄ cubic arrays facilitates electron transfer. The electronic structure of Ni, Co and Mo atoms could be optimized to enhance their electrical conductivity by modulation of N and S atoms. At current densities of 10 and 200 mA cm^-2, N, S-Co₃O₄@NiMoO₄/NF₄₀₀ has an overpotential of 200, 300 and 71 160 mV for the oxygen evolution reaction and hydrogen evolution reaction, respectively. Its water splitting voltages are 1.45 V and 2 V at 10 and 200 mA cm^-2. In addition, N, S-Co₃O₄@NiMoO₄/NF₄₀₀ can operate stably for 100 h at a current density of 50 mA cm^-2. This work provides a new approach to designing bifunctional catalysts with hierarchical heterogeneous structures co-regulated by dual elements.

Semicrystalline IrOx with Abundant Boundaries for Overall Water Splitting

Inorganic compounds with different crystalline and amorphous states may show distinct properties in catalytic applications. In this work, we control the crystallization level by fine thermal treatment and synthesize a semicrystalline IrO_x material with the formation of abundant boundaries. Theoretical calculation reveals that the interfacial iridium with a high degree of unsaturation is highly active for the hydrogen evolution reaction compared to individual counterparts based on the optimal binding energy with hydrogen (H*). At the heat treatment temperature of 500 °C, the obtained IrO_x-500 catalyst has dramatically promoted hydrogen evolution kinetics, endowing the iridium catalyst with a bifunctional activity for acidic overall water splitting with a total voltage of only 1.554 V at a current density of 10 mA cm^-2. In light of the remarkable boundary-enhanced catalysis effects, the semicrystalline material should be further developed for other applications.

In situ phosphoselenization induced heterointerface engineering endow NiSe2/Ni2P/FeSe2 hollow nanocages with efficient water oxidation electrocatalysis performance

Exploiting Earth-abundant and highly effective electrocatalysts toward the oxygen evolution reaction (OER) is critical for boosting water splitting efficiency. Herein, we proposed a novel in situ phosphoselenization strategy to fabricate heterostructured NiSe₂/Ni₂P/FeSe₂ (NiFePSe) nanocages with a modified electronic structure and well-defined nanointerfaces. Owing to the strong interfacial coupling and synergistic effect among the three components, the prepared NiFePSe nanocages exhibit superior OER performance with an ultralow overpotential of 242 mV at 10 mA cm^-2 and a small Tafel slope of 55.8 mV dec^-1 along with robust stability in 1 M KOH. Remarkably, the highly open 3D porous architecture, delicate internal voids, and numerous surface defects endow the NiFePSe nanocages with abundant active sites and enhanced electron mobility. In addition, the super-hydrophilic surface is conducive to facilitating mass transfer between the electrolyte and electrode and rapidly releasing the bubbles. This work may lead to new breakthroughs in the tuning of multi-component transition metal catalysts and the designing of highly active and durable materials for water splitting.

Metallocavitins as Advanced Enzyme Mimics and Promising Chemical Catalysts

The supramolecular approach is becoming increasingly dominant in biomimetics and chemical catalysis due to the expansion of the enzyme active center idea, which now includes binding cavities (hydrophobic pockets), channels and canals for transporting substrates and products. For a long time, the mimetic strategy was mainly focused on the first coordination sphere of the metal ion. Understanding that a highly organized cavity-like enzymatic pocket plays a key role in the sophisticated functionality of enzymes and that the activity and selectivity of natural metalloenzymes are due to the effects of the second coordination sphere, created by the protein framework, opens up new perspectives in biomimetic chemistry and catalysis. There are two main goals of mimicking enzymatic catalysis: (1) scientific curiosity to gain insight into the mysterious nature of enzymes, and (2) practical tasks of mankind: to learn from nature and adopt from its many years of evolutionary experience. Understanding the chemistry within the enzyme nanocavity (confinement effect) requires the use of relatively simple model systems. The performance of the transition metal catalyst increases due to its retention in molecular nanocontainers (cavitins). Given the greater potential of chemical synthesis, it is hoped that these promising bioinspired catalysts will achieve catalytic efficiency and selectivity comparable to and even superior to the creations of nature. Now it is obvious that the cavity structure of molecular nanocontainers and the real possibility of modifying their cavities provide unlimited possibilities for simulating the active centers of metalloenzymes. This review will focus on how chemical reactivity is controlled in a well-defined cavitin nanospace. The author also intends to discuss advanced metal–cavitin catalysts related to the study of the main stages of artificial photosynthesis, including energy transfer and storage, water oxidation and proton reduction, as well as highlight the current challenges of activating small molecules, such as H2O, CO2, N2, O2, H2, and CH4.

Pt-Doped Biomass Carbon Decorated with MoS2 Nanosheets as an Electrocatalyst for Hydrogen Evolution

It is necessary to develop an efficient hydrogen evolution catalyst to improve the efficiency of the hydrogen evolution reaction (HER). Herein, a MoS₂ nanosheet is decorated on the Pt-doping biomass yeast cells (MoS₂@Pt/YC) via a simple hydrothermal process. Reducing the noble metal loading without compromising its performance is a challenging task. The smooth surface of YCs is conducive to the growth of MoS₂ nanosheets, and its functional groups provide attachment sites for metal Pt. The Pt/YC is covered with MoS₂ nanosheets, thus improving the exposed active sites for HER. The obtained MoS₂@Pt/YC delivers a competitive overpotential of 118 mV at the benchmark current density of 10 mA cm^-2 and achieves a small Tafel slope of 74 mV dec^-1, indicating the great HER performance of MoS₂@Pt/YC. Moreover, MoS₂@Pt/YC shows robust stability after 24 h of continuous operation toward HER in acidic solution. By introducing transition metal sulfides with high specific surface area, the loading of precious metals can be reduced without compromising properties. This work provides a method to design Pt-doping HER electrocatalysts through a simple method. The facile preparation process for MoS₂@Pt/YC and its outstanding performance allow it to be a promising electrocatalyst for practical HER application.