Electronic structure engineering on Co-based metal-organic frameworks for concurrent electrocatalytic hydrogen generation and formate electrosynthesis.

A facile one-step solvothermal method was developed to synthesize Ir-doped Co-based metal-organic framework (CoIr-MOF) nanoarrays as a bifunctional electrocatalyst for water-glucose co-electrolysis. It was demonstrated that in situ incorporation of a low-content of Ir cations could modulate the electronic structure of Co active centers and thus boost the electrocatalytic performance towards both the hydrogen evolution reaction and glucose-to-formate oxidation reaction.

Yttrium atomically incorporated into Co(OH)F nanowires enables efficient electrochemical reduction of nitrate to ammonia.

A new kind of electrocatalyst consisting of yttrium-doped Co(OH)F (Y-Co(OH)F) nanowires was synthesized by one hydrothermal method for nitrate electroreduction to ammonia. It was demonstrated that the rare earth element Y, as an oxophilic metal, can be approximated as Lewis acid sites enhancing nitrate adsorption on the catalyst surface. Therefore, the Y-Co(OH)F exhibits excellent nitrate reduction performance, reaching an optimal ammonia production rate of 0.2149 mmol h-1 cm-2 and ammonia faradaic efficiency of 91.81%.

Electrochemical Postmodification-Induced Surface Atom Rearrangement over Cu Nanodendrites for Enhanced Electrosynthesis of Ammonia from Nitrate.

Utilizing nitrate from wastewater as a N-source for ammonia synthesis via electrocatalysis is of significance for both environmental protection and ecological nitrogen cycle balance, which requires high-performance electrocatalysts to drive selective nitrate-to-ammonia transformation. In this work, an electrochemical postmodification strategy was developed to regulate the surface structure of presynthesized Cu nanodendrites at the atomic level. A combination of physicochemical characterization and electrochemical study demonstrates that such a treatment could induce surface Cu atom rearrangement and result in increased electrochemically active surface area and high density of surface-active sites, disclosing a high electrocatalytic nitrate-to-ammonia capability, with an optimal NH3 yield rate of 0.2238 mmol h-1 cm-2 and a corresponding Faradaic efficiency of 94.43%. This study may provide a guiding design avenue for atomic arrangement engineering of metallic nanocrystals via electrochemical postmodification for nitrate reduction reaction and other energy conversion electrocatalysis.

Interface Engineering and Boron Modification of Pd-B/Pd Hetero-Metallene Synergistically Accelerate Oxygen Reduction Catalysis.

2D metallene possess high surface area and excellent electron transport capability, thus enabling efficient application in oxygen reduction reaction (ORR). However, the interface regulation and electronic structure optimization of metallene are still great challenges. Herein, Pd-B/Pd hetero-metallene is constructed by interface engineering and B modification strategies for efficient electrocatalytic ORR. The 2D configuration of Pd-B/Pd hetero-metallene exposes a large number of surface atoms and unsaturated defect sites, thus providing abundant catalytic active sites and exhibiting high electron mobility. More importantly, interface engineering and B modification synergistically optimizing the electronic configuration of the metallene system. This work not only provides an effective strategy for the rational regulation of the electronic configuration of metallene, but also offers a reference for the construction of efficient ORR catalysts.

Sustainable Ammonia Electrosynthesis from Nitrate Wastewater Coupled to Electrocatalytic Upcycling of Polyethylene Terephthalate Plastic Waste.

Integrating the nitrate reduction reaction (NO3RR) with polyethylene terephthalate (PET) hydrolysate oxidation to construct the nitrate/PET hydrolysate coelectrolysis system holds a great promise of realizing the simultaneous upcycling of nitrate wastewater and PET plastic waste, which, however, is still an almost untouched research area. Herein, we develop an ultralow content of Ru-incorporated Co-based metal-organic frameworks as a bifunctional precatalyst, which can be in situ reconstructed to Ru-Co(OH)2 at the cathode and Ru-CoOOH at the anode under electrocatalytic environments, and function as real active catalysts for the NO3RR and PET hydrolysate oxidation, respectively. With a two-electrode nitrate/PET hydrolysate coelectrolysis system, the current density of 50 mA cm-2 is achieved at a cell voltage of only 1.53 V, realizing the simultaneous production of ammonia and formate at a lower energy consumption. This study provides a concept for the construction of coelectrolysis systems for upcycling of nitrate wastewater and PET plastic waste.

Yttrium-doped cobalt-based metal-organic frameworks for selective electrooxidation of glycerol coupled with hydrogen production.

A facile strategy was developed for one-step synthesis of yttrium(Y)-doped cobalt-based metal-organic framework (CoY-MOF) nanosheet arrays. It was demonstrated that in situ doping with a low content of Y can tailor the electronic structure of the MOF structures, thereby improving their electrocatalytic performance for both hydrogen evolution and glycerol oxidation reactions.

Electronic Metal-Support Interaction Triggering Interfacial Charge Polarization over CuPd/N-Doped-C Nanohybrids Drives Selectively Electrocatalytic Conversion of Nitrate to Ammonia.

Selective electrocatalytic nitrate-to-ammonia conversion holds significant potential in treatment of nitrate wastewater and simultaneously produces high-value-added ammonia. However, today's development of nitrate-to-ammonia technology remains hindered by the lack of electrocatalysts with high activity and selectivity. In this work, metal-organic framework-derived CuPd bimetallic nanoparticles/nitrogen-doped carbon (CuPd/CN) hybrid nanoarrays for efficient ammonia electrosynthesis from nitrate are designed and synthesized. Systematic characterization reveals that the electronic metal-support interaction between the CuPd nanoparticles and N-doped nanocarbon matrix could trigger interfacial charge polarization over the CuPd/CN composite and make Cu sites electron deficient, which is conducive to the adsorption of nitrate ions. Moreover, the Pd atom sites separate by Cu atoms and could catalyze the dissociation of H2 O molecules to form adsorbed H species, which evolves into hydrogen radicals and behaves as the dominant reactive species in accelerating nitrate-to-ammonia electrocatalysis. These advantages endow the CuPd/CN nanoarrays with high faradaic efficiency (96.16%), selectivity (92.08%) as well as excellent catalytic stability for electroreduction of nitrate to ammonia.

Controllable reconstruction of copper nanowires into nanotubes for efficient electrocatalytic nitrate conversion into ammonia.

The electrochemical reduction of nitrate to ammonia provides a green and delocalized route for ammonia synthesis under ambient conditions, which requires advanced catalysts with high activity and selectivity. In this work, we propose a two-step conversion strategy to construct hierarchical copper nanosheet-based Cu nanotubes using pre-synthesized Cu nanowires as the starting material for the electrocatalytic nitrate reduction reaction (NO3RR). The conversion of Cu nanowires into Cu nanotubes could be realized through chemical oxidation followed by in situ electrochemical reduction, enabling the effective engineering of active sites and thus boosting the electrocatalytic nitrate-to-ammonia capability. Such a controllable reconstruction strategy provides a new avenue for constructing high-performance electrocatalysts for sustainable NH3 synthesis and the elimination of NO3- contamination.

Two-Dimensional Heterojunction Electrocatalyst: Au-Bi2Te3 Nanosheets for Electrochemical Ammonia Synthesis.

The design of Au-based materials with good dispersion and more active sites is critical to enhance the catalytic performance of electrochemical ammonia production. Herein, two-dimensional (2D) heterojunction Au-Bi2Te3 nanosheets (Au-Bi2Te3 NSs) are prepared by Au nanoparticles growing on Bi2Te3 nanosheets. Benefiting from the good dispersion of Au nanoparticles and the synergistic effect of the heterojunction composite, Au-Bi2Te3 NSs demonstrate excellent behavior for an ambient nitrogen reduction reaction (NRR). In a 0.1 M Na2SO4 electrolyte (N2-saturated), Au-Bi2Te3 NSs display a high NH3 yield rate of 32.73 µg h-1 mgcat.-1 and a faradic efficiency of 20.39% at -0.4 V. The proposed synthetic method provides a feasible strategy for designing high-performance heterojunction electrocatalysts for electrochemical ammonia synthesis.

Synergism of Interfaces and Defects: Cu/Oxygen Vacancy-Rich Cu-Mn3O4 Heterostructured Ultrathin Nanosheet Arrays for Selective Nitrate Electroreduction to Ammonia.

Achieving high efficiency in nitrate (NO3-) to ammonia (NH3) electrocatalysis requires the exploration of advanced electrocatalysts with a well-designed composition and architecture. In this work, a facile one-step hydrothermal approach was developed for the construction of novel Cu/oxygen vacancy-rich Cu-Mn3O4 heterostructured ultrathin nanosheet arrays on Cu foam (Cu/Cu-Mn3O4 NSAs/CF). Two-dimensional ultrathin nanosheet arrays could increase the exposure of catalytically active centers, and the heterogeneous nanointerface and oxygen vacancies synergistically improve the nitrate-to-ammonia activity over the active centers. Due to the desirable compositional and structural advantages, the Cu/Cu-Mn3O4 NSAs/CF demonstrated excellent performance for the electrocatalytic nitrate reduction to ammonia with high ammonia selectivity (87.6%) and Faradic efficiency (92.4%).

Cooperativity of Cu and Pd active sites in CuPd aerogels enhances nitrate electroreduction to ammonia.

By rationally choosing Pd as an active metal and Cu as a promoting metal, we developed Cu-rich CuPd bimetallic aerogels as a self-supported electrocatalyst for nitrate electroreduction. The spongy aerogel structure provides abundant catalytically active sites, while the synergistic benefit of the CuPd binary composition increases their reactivity, helping to achieve efficient nitrate-to-ammonia conversion.

Two-Dimensional NiIr@N-Doped Carbon Nanocomposites Supported on Ni Foam for Electrocatalytic Overall Water Splitting.

Electrochemical water splitting can provide a promising avenue for sustainable hydrogen production. Highly efficient electrocatalysts toward the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) are extremely important for the practical application of water splitting technology. Herein, a one-step annealing strategy is reported for the fabrication of a metal-organic framework-derived bifunctional self-supported electrocatalyst, which is composed of two-dimensional N-doped carbon-wrapped Ir-doped Ni nanoparticle composites supported on Ni foam (NiIr@N-C/NF). The resultant NiIr@N-C/NF displays excellent electrocatalytic performance in 1.0 m KOH, with low overpotentials of 32 mV at 10 mA cm-2 for the HER and 329 mV at 50 mA cm-2 for the OER. Particularly, the HER-OER bifunctional NiIr@N-C/NF needs only 1.50 V to yield 10 mA cm-2 for overall water splitting.

Hydrophilic/Aerophobic Hydrogen-Evolving Electrode: NiRu-Based Metal-Organic Framework Nanosheets In Situ Grown on Conductive Substrates.

Electrocatalytic reduction of water via hydrogen evolution reaction (HER) is considered one of the most ideal avenues to produce high-purity hydrogen (H2) in large quantities, which always requires active electrocatalysts to overcome the high energy barrier. It is of significance yet challenging to design and construct effective HER electrocatalysts of an acceptable cost. In this study, a highly efficient metal-organic framework (MOF)-based electrochemical HER system based on NiRu-based binary MOF (Ru-doped Ni2(BDC)2TED MOF, BDC = 1,4-benzenedicarboxylic acid; TED = triethylenediamine) nanosheets grown on conductive substrates (e.g., Ni foam, carbon cloth) is fabricated by a facile solvothermal method. The resultant NiRu-MOF-based composites possess enhanced electron transport ability and water stability, accompanied by increased electrochemically active areas and hydrophilic/aerophobic properties. With these advantages, the optimized NiRu-MOF nanosheet arrays on Ni foam substrate (NiRu-MOF/NF) with a Ru/Ni molar ratio of 6/94 in the MOF structure could exhibit efficient catalytic performance for HER in alkaline conditions, requiring a small overpotential of 51 mV at -10 mA cm-2. This study could provide a feasible way for the design and synthesis of two-dimensional (2D) MOF-based materials with controllable interface properties for energy catalysis and beyond.

Ir-Doped Ni-based metal-organic framework ultrathin nanosheets on Ni foam for enhanced urea electro-oxidation.

Low-Ir-content-doped Ni-based metal-organic framework (Ir-doped Ni2(BDC)2TED MOF, BDC = 1,4-benzenedicarboxylic acid, TED = triethylenediamine) ultrathin nanosheets grown on a nickel foam substrate (NiIr-MOF/NF) were synthesized by a facile solvothermal method. The as-synthesized NiIr-MOF/NF composite electrode could bring about increased electrochemical active area, accelerated electron transport capability as well as improved stability, which facilitate the urea oxidation reaction (UOR) electrocatalysis.

Synergism of Interface and Electronic Effects: Bifunctional N-Doped Ni3 S2 /N-Doped MoS2 Hetero-Nanowires for Efficient Electrocatalytic Overall Water Splitting.

The realization of water electrolysis on the basis of highly active, cost-effective electrocatalysts is significant yet challenging for achieving sustainable hydrogen production from water. Herein, N-doped Ni3 S2 /N-doped MoS2 1D hetero-nanowires supported by Ni foam (N-Ni3 S2 /N-MoS2 /NF) are readily synthesized through a chemical transformation strategy by using NiMoO4 nanowire array growth on Ni foam (NiMoO4 /NF) as the starting material. With the in situ generation of Ni3 S2 /MoS2 heterointerfaces within nanowires and the incorporation of N- anions, an extraordinary hydrophilic nature with abundant, well-exposed active sites and optimal reaction dynamics for both oxidation and reduction of water are obtained. Attributed to these properties, as-converted N-Ni3 S2 /N-MoS2 /NF exhibits highly efficient electrocatalytic activities for both hydrogen and oxygen evolution reactions under alkaline conditions. The superior bifunctional properties of N-Ni3 S2 /N-MoS2 /NF enable it to effectively catalyze the overall water-splitting reaction.