RESUMEN

Hematite (α-Fe2O3) has become a research hotspot in the field of photoelectrochemical water splitting (PEC-WS), but the low photogenerated carrier separation efficiency limits further application. The electronic structure regulation, such as element doping and organic functional groups with different electrical properties, is applied to alleviate the problems of poor electrical conductivity, interface defects, and band mismatch. Herein, α-Fe2O3 photoanodes are modified to regulate their electric structures and improve photogenerated carrier transport by the bimetallic metal-organic frameworks (MOFs), which are constructed with Fe/Ni and terephthalate (BDC) with 2-substitution of different organic functional groups (─H, ─Br, ─NO2 and ─NH2). The α-Fe2O3 photoanode loaded with FeNi-NH2BDC MOF catalyst exhibits the optimal photocurrent density (2 mA cm-2) at 1.23 VRHE, which is 2.33 times that of the pure α-Fe2O3 photoanode. The detailed PEC analyses demonstrate that the bimetallic synergistic effect between Fe and Ni can improve the conductivity and inhibit the photogenerated carrier recombination of α-Fe2O3 photoanodes. The ─NH2 group as an electron-donor group can effectively regulate the electron distribution and band structure of α-Fe2O3 photoanodes to prolong the lifetime of photogenerated holes, which facilitates photogenerated carrier transport and further enhances the PEC-WS performance of α-Fe2O3 photoanode.

RESUMEN

Constructing dual-site catalysts consisting of atomically dispersed metal single atoms and metal atomic clusters (MACs) is a promising approach to further boost the catalytic activity for oxygen reduction reaction (ORR). Herein, a porous CoSA-AC@SNC featuring the coexistence of Co single-atom sites (CoN4) and S-coordinated Co atomic clusters (SCo6) in S, N co-doped carbon substrate is successfully synthesized by using porphyrinic metal-organic framework (Co-TPyP MOF) as the precursor. The introduction of the sulfur source creates abundant microstructural defects to anchor Co metal clusters, thus modulating the electronic structure of its surrounding carbon substrate. The synergistic effect between the two types of active sites and structural advantages, in turn, results in high ORR performance of CoSA-AC@SNC with half-wave potential (E1/2) of 0.86 V and Tafel slope of 50.17 mV dec-1. Density functional theory (DFT) calculations also support the synergistic effect between CoN4 and SCo6 by detailing the catalytic mechanism for the improved ORR performance. The as-fabricated Zn-air battery (ZAB) using CoSA-AC@SNC demonstrates impressive peak power density of 174.1 mW cm-2 and charge/discharge durability for 148 h. This work provides a facile synthesis route for dual-site catalysts and can be extended to the development of other efficient atomically dispersed metal-based electrocatalysts.

RESUMEN

Doping transition metal oxide spinels with metal ions represents a significant strategy for optimizing the electronic structure of electrocatalysts. Herein, a bimetallic Fe and Ru doping strategy to fine-tune the crystal structure of CoV2O4 spinel for highly enhanced oxygen evolution reaction (OER) is presented performance. The incorporation of Fe and Ru is observed at octahedral sites within the CoV2O4 structure, effectively modulating the electronic configuration of Co. Density functional theory calculations have confirmed that Fe acts as a novel reactive site, replacing V. Additionally, the synergistic effect of Fe, Co, and Ru effectively optimizes the Gibbs free energy of the intermediate species, reduces the reaction energy barrier, and accelerates the kinetics toward OER. As expected, the best-performing CoVFe0.5Ru0.5O4 displays a low overpotential of 240 mV (@10 mA cm-2) and a remarkably low Tafel slope of 38.9 mV dec-1, surpassing that of commercial RuO2. Moreover, it demonstrates outstanding long-term durability lasting for 72 h. This study provides valuable insights for the design of highly active polymetallic spinel electrocatalysts for energy conversion applications.

RESUMEN

Development of non-noble metal-based electrocatalysts to enhance the performance of zinc-air batteries (ZABs) is of great significance, but it remains a formidable challenge due to their poor stability and activity. Herein, a bifunctional CuNi-TiOx/NCNFS electrocatalyst, featuring with electron-rich copper-nickel (CuNi) alloy nanoparticles anchored on titanium oxide/N-doped carbon nanofibers (TiOx/NCNFS), is constructed by a dual-substrate loading strategy. The introduction of TiOx has led to a significant increase in the stability of the dual-substrate. The strong electronic interaction between CuNi and TiOx strengthens the anchoring of active metal sites, thus accelerating the electron transfer. Theoretical calculations unclose that NCNFS can regulate the charge distribution of TiOx, inducing the charge transfer from NCNFS â†’ TiOx â†’ CuNi, thereby reducing the d-band center of Cu and Ni, which is beneficial to the desorption of intermediate oxide species of the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). Therefore, CuNi-TiOx/NCNFS delivers a remarkable bifunctional performance with a low OER overpotential of 258 mV at 10 mA cm-2 and an ORR half-wave potential of 0.85  V. When assembled into ZABs, CuNi-TiOx/NCNFS shows a low potential gap of 0.64 V, a higher power density of 149.6 mW cm-2 at 330 mA cm-2, and an outstanding stability for 250 h at 5mA cm-2. This study provides a novel approach by constructing dual-substrate to tune the electronic structure of active metal sites for efficient rechargeable ZABs.

RESUMEN

Spinel oxides have emerged as a promising candidate in the realm of nanozymes with variable oxidation states, while their limited active sites and low conductivity hinder further application. In this work, we synthesize a series of metal-doped NiCo2O4 nanospheres decorated with Pd, which are deployed as highly efficient nanozymes for the detection of cancer biomarkers. Through meticulous modulation of the molar ratio between NiCo2O4 and Pd, we orchestrated precise control over the oxygen vacancies and electronic structure within the nanozymes, a key factor in amplifying the catalytic prowess. Leveraging the superior H2O2 reduction catalytic properties of Fe-NiCo2O4@Pd, we have successfully implemented its application in the electrochemical detection of biomarkers, achieving unparalleled analytical performance, much higher than that of Pd/C and other reported nanozymes. This research paves the way for innovative electron modification strategies in the design of high-performance nanozymes, presenting a formidable tool for clinical diagnostic analyses.

Asunto(s)

Cobalto , Peróxido de Hidrógeno , Óxidos , Paladio , Catálisis , Paladio/química , Cobalto/química , Óxidos/química , Peróxido de Hidrógeno/química , Oxidación-Reducción , Níquel/química , Humanos , Técnicas Electroquímicas

RESUMEN

Bimetallic alloy nanoparticles have garnered substantial attention for diverse catalytic applications owing to their abundant active sites and tunable electronic structures, whereas the synthesis of ultrafine alloy nanoparticles with atomic-level homogeneity for bulk-state immiscible couples remains a formidable challenge. Herein, we present the synthesis of RuxCo1-x solid-solution alloy nanoparticles (ca. 2 nm) across the entire composition range, for highly efficient, durable, and selective CO2 hydrogenation to CH4 under mild conditions. Notably, Ru0.88Co0.12/TiO2 and Ru0.74Co0.26/TiO2 catalysts, with 12 and 26 atom % of Ru being substituted by Co, exhibit enhanced catalytic activity compared with the monometallic Ru/TiO2 counterparts both in dark and under light irradiation. The comprehensive experimental investigations and density functional theory calculations unveil that the electronic state of Ru is subtly modulated owing to the intimate interaction between Ru and Co in the alloy nanoparticles, and this effect results in the decline in the CO2 conversion energy barrier, thus ultimately culminating in an elevated catalytic performance relative to monometallic Ru and Co catalysts. In the photopromoted thermocatalytic process, the photoinduced charge carriers and localized photothermal effect play a pivotal role in facilitating the chemical reaction process, which accounts for the further boosted CO2 methanation performance.

RESUMEN

The electrocatalytic performance of single-site catalysts (SSCs) is closely correlated with the electronic structure of metal atoms. Herein we construct a series of Pt SSCs on heteroatom-doped hierarchical carbon nanocages, which exhibit increasing hydrogen evolution reaction (HER) activities along S-doped, P-doped, undoped and N-doped supports. Theoretical simulation indicates a multi-H-atom adsorption process on Pt SSCs due to the low coordination, and a reasonable descriptor is figured out to evaluate the HER activities. Relative to C-coordinated Pt, N-coordinated Pt has higher reactivity due to the electron transfer of N-to-Pt, which enriches the density of states of Pt 5d orbital near the Fermi level and facilitates the capturing of protons, just the opposite to the situations for P- and S-coordinated ones. The stable N-coordinated Pt originates from the kinetic stability throughout the multi-H-atom adsorption process. This finding provides a significant guidance for rational design of advanced Pt SSCs on carbon-based supports.

RESUMEN

Transition metal phosphides (TMPs) have been widely studied for water decomposition for their monocatalytic property for anodic or cathodic reactions. However, their bifunctional catalytic activity still remains a major challenge. Herein, hexagonal nickel-cobalt bimetallic phosphide nanoneedles with 1-3 µm length and 15-30 nm diameter supported on NF (NixCo2-xP NDs/NF) with adjusted electron structure have been successfully prepared. The overall alkaline water electrolyzer composed of the optimal anode (Ni0.67Co1.33P NDs/NF) and cathode (Ni1.01Co0.99P NDs/NF) provide 100 mA cm-2 at 1.62 V. Gibbs Free Energy for reaction paths proves that the active site in the hydrogen evolution reaction (HER) is Ni and the oxygen evolution reaction (OER) is Co in NixCo2-xP, respectively. In the HER process, Co-doping can result in an apparent accumulation of charge around Ni active sites in favor of promoting HER activity of Ni sites, and ΔGH* of 0.19 eV is achieved. In the OER process, the abundant electron transfer around Co-active sites results in the excellent ability to adsorb and desorb *O and *OOH intermediates and an effectively reduced ∆GRDS of 0.37 eV. This research explains the regulation of electronic structure change on the active sites of bimetallic materials and provides an effective way to design a stable and effective electrocatalytic decomposition of alkaline water.

RESUMEN

Lithium metal batteries are deemed as an optimal candidate for the next generation of durable energy storage devices. However, the growth of lithium dendrite and significant volume expansion pose as obstacles that impede the application of lithium metal batteries. In this work, a functional copper current collector was designed by coating it with Co-doped ZnO (Co/ZnO) to enhance the lithiophilicity through local electric fields and built-in magnetic fields induced by the ferromagnetic material. The incorporation of Co not only induces a local electric field and thus accelerating electron transfer, but also imparts the ferromagnetic behavior to ZnO, resulting in an internal magnetic field to regulate the dynamic trajectory. Profiting from the above advantages, the symmetric cells have excellent cycle stability in 1 mA cm-2 and 1 mAh cm-2 , maintaining ultra-low voltage for over 2000 h. This study provides a realizable pathway for next-generation current collector of copper modification.

RESUMEN

Cobalt spinel oxides, which consist of tetrahedral site (AO4) and octahedral site (BO6), are a potential group of transition metal oxides (TMO) for electrocatalytic nitrate reduction reactions to ammonia (NRA). Identifying the true active site in spinel oxides is crucial to designing advanced catalysts. This work reveals that the CoO6 site is the dominant site for NRA through the site substitution strategy. The suitable electronic configuration of Co at the octahedral site leads to a stronger interaction between the Co d-orbital and the O p-orbital in O-containing intermediates, resulting in a high-efficiency nitrate-to-ammonia reduction. Furthermore, the substitution of metallic elements at the AO4 site can affect the charge density at the BO6 site via the structure of A-O-B. Thereafter, Ni and Cu are introduced to replace the tetrahedral site in spinel oxides and optimize the electronic structure of CoO6. As a result, NiCo2O4 exhibits the best activity for NRA with an outstanding yield of NH3 (15.49 mg cm-2 h-1) and FE (99.89%). This study introduces a novel paradigm for identifying the active site and proposes an approach for constructing high-efficiency electrocatalysts for NRA.

RESUMEN

Transition metal sulfides (TMS) have been considered as a promising group of electrode materials for supercapacitors as a result of their strong redox activity, but high volumetric strain of the materials during electrochemical reactions causes rapid structural collapse and severe capacity loss. Herein, we have synthesized phosphorus-doped (P-doped) Ni2S3/Co3S4/ZnS battery-type nanowire/nanosheet arrays as an advanced cathode for supercapacitor through a two-step process of hydrothermal and annealing treatments. The material has a one-dimensional nanowire/two-dimensional nanosheet-like coexisting microscopic morphology, which facilitates the exposure of abundant active centers and promotes the transport and migration of ions in the electrolyte, while the doping of P significantly enhances the conductivity of the electrode material. Simultaneously, the element phosphorus with similar atomic radii and electronegativity to sulfur may act as electron donors to regulate the electron distribution, thus providing more effective electrochemically active sites. In gratitude to the synergistic effect of microstructure optimization and electronic structure regulation induced by the doing of P, the P-Ni2S3/Co3S4/ZnS nanoarrays provide a superior capacity of 2716 F g-1 at 1 A/g, while the assembled P-Ni2S3/Co3S4/ZnS//AC asymmetric supercapacitor exhibits a high energy density of 48.2 Wh kg-1 at a power density of 800 W kg-1 with the capacity retention of 89 % after 9000 cycles. This work reveals a possible method for developing high-performance transition metal sulfide-based battery-like electrode materials for supercapacitors through microstructure optimization and electronic structure regulation.

RESUMEN

Catalytically inactive Zn2+ is incorporated into cobalt hydroxide to synthesize hierarchical ZnCo-layered double hydroxide nanosheet networks supported on carbon fiber (ZnCo-LDH/CF). The incorporation of Zn2+ is revealed to endow ZnCo-LDH/CF with significantly superior performance in the aspects of the activity and selectivity for methanol electrooxidation to formic acid and the boosting effect for cathodic hydrogen production compared with the counterpart without Zn2+. Density functional theory (DFT) calculation reveals that the incorporation of nonactive Zn2+ can increase the density of states near the Fermi level of LDH (i.e., elevate electrical conductivity to form favorable charge transportation during electrocatalysis) and promote the adsorption and subsequent cleavage of methanol, thus leading to the enhanced methanol electrooxidation performance.

RESUMEN

Unreasonable accumulation of coal gangue in mining area has become the major source of global pollution. Probing the high-valued utilization of coal gangue has become a key approach to address the problem. Herein, a promising catalyst of MoO2 @coal gangue with amorphous/crystalline heterostructure derived from mine solid waste, which acts as an efficient cathode for Li-O2 batteries is first reported. Impressively, the as-prepared catalyst exhibits a favorable initial discharge capacity of 9748 mAh g-1 and promising long-term cyclic stability over 2200 h. Experimental results coupled with density functional theory (DFT) analysis reveal that the synergistic interaction between high-activity MoO2 and stable SiO2 , unique amorphous/crystalline heterostructure and the modified interfacial adsorption of LiO2 intermediate are critical factors in promoting the electrochemical performance. This work provides a new insight to design marked electrocatalysts by mine solid waste for Li-O2 batteries.

RESUMEN

Layered double hydroxides (LDHs) are promising electrocatalytic materials for the oxygen evolution reaction (OER) due to their tunable composition and low cost. Here, we construct ultrathin Al-incorporated Co LDH nanosheets on carbon cloth (CC) by a facile hydrothermal strategy. Compared to Co LDH/CC, the optimized Co2Al1 LDH/CC displays significantly improved OER performance, characterized by low overpotentials of only 171 and 200 mV to reach current densities of 10 mA cm-2 in alkaline and neutral media, respectively, as well as good stability over an extended period. The introduced Al3+ and CC support play a synergistic role in steering the morphology of Co2Al1 LDH/CC while also increasing the electrochemical active sites. X-ray absorption fine spectra (XAFS) analyses uncover the critical role of Al in regulating the coordination environment of Co atoms, with evidence affording highly active Co oxidation states. Moreover, density functional theory (DFT) calculations confirmed that the Al3+ incorporated into Co LDH/CC can efficaciously modulate the electronic density of states of the d-band center of Co atoms, optimize the Gibbs free energies of intermediates toward OER, and thus accelerate the O2 evolution rate.

RESUMEN

To develop a non-precious highly efficient cocatalyst to replace Pt on graphitic carbon nitride (g-C3 N4 ) for solar H2 production is great significant, but still remains a huge challenge. The emerging single-atom catalyst presents a promising strategy for developing highly efficient non-precious cocatalyst owing to its unique adjustability of local coordination environment and electronic structure. Herein, this work presents a facile approach to achieve single Ni sites (Ni1 -N2 S) with unique local coordination structure featuring one Ni atom coordinated with two nitrogen atoms and one sulfur atom, confirmed by high-angle annular dark-field scanning transmission electron microscopy, X-ray absorption spectroscopy, and density functional theory calculation. Thanks to the unique electron structure of Ni1 -N2 S sites, the 1095 µmol g-1 h-1 of high H2 evolution rate with 4.1% of apparent quantum yield at 420 nm are achieved. This work paves a pathway for designing a highly efficient non-precious transition metal cocatalyst for photocatalytic H2 evolution.

RESUMEN

Nitrous oxide (N2O) has gained increasing attention as an important noncarbon dioxide greenhouse gas, and catalytic decomposition is an effective method of reducing its emissions. Here, Co3O4 was synthesized by the sol-gel method and single-atom Pr was confined in its matrix to improve the N2O decomposition performance. It was observed that the reaction rate varied in a volcano-like pattern with the amount of doped Pr. A N2O decomposition reaction rate 5-7.5 times greater than that of pure Co3O4 is achieved on the catalyst with a Pr/Co molar ratio of 0.06:1, and further Pr doping reduced the activity due to PrOx cluster formation. Combined with X-ray photoelectron spectroscopy, X-ray absorption fine structure, density functional theory and in situ near-ambient pressure X-ray photoelectron spectroscopy, it was demonstrated that the single-atom doped Pr in Co3O4 generates the "Pr 4f-O 2p-Co 3d" network, which redistributes the electrons in Co3O4 lattice and increases the t2g electrons at the tetracoordinated Co2+ sites. This coupling between the Pr 4f orbit and Co2+ 3d orbit triggers the formation of a 4f-3d electronic ladder, which accelerates the electron transfer from Co2+ to the 3π* antibonding orbital of N2O, thus contributing to the N-O bond cleavage. Moreover, the energy barrier for each elementary reaction in the decomposition process of N2O is reduced, especially for O2 desorption. Our work provides a theoretical grounding and reference for designing atomically modified catalysts for N2O decomposition.

RESUMEN

Urea electrooxidation with favorable thermodynamic potential is highly anticipated but suffering from sluggish kinetics. Deciphering the activity origin and achieving rational structure design are pivotal for developing highly efficient electrocatalyst for urea oxidation reaction (UOR). Herein, nitrogen penetrated nickel nanoparticles confined in carbon nanotubes (Ni-NCNT) is successfully achieved to drive UOR. Active origin of Ni-NCNT is decoded to be the in-situ generated Ni2+δO(OH)ads according to comprehensive analysis. The electrophilic Ni2+δ and protophilic OHads could targeted capture O and H atoms from urea, respectively, achieving molecule activation and accelerating the subsequent proton coupled electron transfer reactions. Nitrogen penetration is identified to promote prior formation of Ni2+δO(OH)ads and push up the d band center of Ni-NCNT, enhancing urea adsorption and subsequent molecule cleavage reactions. As a result, Ni-NCNT exhibits superior UOR performance. This work supplies valuable insights for the rational design and construction of efficient nickel-based catalyst for driving UOR.

RESUMEN

Electronic structure of single-atom catalysts (SACs) is critical for bifunctional oxygen electrocatalysis by adjusting the binding energy in oxygen-containing intermediates. However, the regulation of electronic structure has always been a challenge to improve catalytic reactivity. Herein, by introducing a heterogenous metal, the electronic structure through a direct bonding interaction to the active center atom is effectively adjusted. Partial charge transfer between the two atoms optimizes the binding energy of intermediates and reducing the energy barrier of the catalytic reaction. Theoretical calculations confirm these effects and the uniform distribution of 3d orbitals, leading to the improvement of bifunctional oxygen electrocatalytic reactivity. Benefiting from these attributes, the as-constructed bifunctional catalyst enables outstanding electrocatalytic performances in both oxygen reduction and hydrogen oxidation in various energy storage systems. The generality and expandability of this strategy is demonstrated by further successful development of other dual-metal catalysts systems with various active metals.

RESUMEN

Developing highly efficient bifunctional catalysts for the oxygen reduction and oxygen evolution reaction (ORR/OER) can open possibilities for future zinc air batteries (ZABs). Herein, cost-effective and highly conductive few-layer ferric and nickel chloride co-intercalated graphite intercalation compounds (FeCl3 -NiCl2 -GIC) are designed as bifunctional oxygen catalysts for ZAB. The optimized few-layer FeCl3 -NiCl2 -GIC catalyst exhibits a small overpotential of 276 mV at 10 mA cm-2 for the OER and achieves a high onset potential of 0.89 V for the ORR. The theoretical analysis demonstrates the electron-rich state on the carbon layers of FeCl3 -NiCl2 -GIC during the catalytic process favors the kinetics of electron transfer and lowers the absorption energy barriers for intermediates. Impressively, the ZAB assembled with few-layer FeCl3 -NiCl2 -GIC catalyst displays a 160 h cycling stability and a high energy efficiency of 72.6%. This work also suggests the possibility of utilizing layer electronic structure regulation on graphite intercalation compounds as effective bifunctional catalysts for ZABs.

RESUMEN

Aluminum-air batteries (AABs) are deemed as a potential clean energy storage device. However, exploiting high-efficiency and stable oxygen reduction reaction (ORR) electrocatalysts in AABs is still a challenge. Iron phthalocyanine (FePc) shows a great prospect in ORR but still far from Pt-based catalysts. Here, the hybrid electrocatalysts of monolayer FePc and hollow N,S-doped carbon spheres (HNSCs) are innovatively constructed through π-π stacking to achieve high dispersion. The resulting FePc@HNSC catalyst exhibits an outstanding ORR activity, outperforming that of pristine FePc and even most Fe-based catalysts reported to date. Moreover, the AAB using FePc@HNSC catalyst not only demonstrates a superior power density than the battery with Pt/C, but also displays stable discharge voltages and excellent durability. Furthermore, the theoretical calculations confirm that the charge distribution and d-band center of the Fe atom in FePc are efficiently optimized by hybrid configuration via the introduction of N,S-doped carbon substrate. The design leads to an enriched electron density around Fe active sites and significant reduction of energy barrier for OH* formation, which are favorable for the improvement of electrocatalytic ORR performance. This work provides a chance to expand the application of metallic macrocyclic compound electrocatalysts in various energy technologies.