Metal Oxide Heterostructures Research Articles

High-Entropy Prussian Blue Analogue Derived Heterostructure Nanoparticles as Bifunctional Oxygen Conversion Electrocatalysts for the Rechargeable Zinc-Air Battery.

In response to energy challenges, rechargeable zinc-air batteries (RZABs) serve as an ideal platform for energy storage with a high energy density and safety. Nevertheless, addressing the sluggish oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in RZAB requires highly active and robust electrocatalysts. High-entropy Prussian blue analogues (HEPBAs), formed by mixing diverse metals within a single lattice, exhibit enhanced stability due to their increased mixing entropy, which lowers the Gibbs free energy. HEPBAs innately enable sacrificial templating, an effective way to synthesize complex structures. Impressively, in this study, we successfully transform HEPBAs into exquisite multiphase (multimetallic alloy, metal carbide, and metal oxide) heterostructure nanoparticles through a controlled synthesis process. The elusive multiphase heterostructure nanoparticles manifested two active sites for selective ORR and OER. By integrating CNT into HEPBA-derived nanoparticles (HEPBA/CNT-800), the HEPBA/CNT-800 demonstrates superior activity toward both ORR (E1/2 = 0.77 V) in a 0.1 M KOH solution and the OER (η = 330 mV at 50 mA cm-2) in a 1 M KOH solution. The RZAB with a HEPBA/CNT-based air electrode demonstrated an open-circuit voltage of 1.39 V and provided a significant energy density of 71 mW cm-2. Moreover, the charge and discharge cycles lasting up to 40 h at a current density of 5 mA cm-2 demonstrate its excellent stability. This work provides an alternative avenue for the rational design of HEPBA's derivative for a sustainable rechargeable metal-air battery platform.

Machine Learning Accelerated Identification of Bifunctional Active Sites in Metal-Organic Framework Derived Metal Oxide Heterostructures for High-Performance Zinc-Air Batteries

The demand for electrochemical energy storage (ESS) systems and their market size has drastically increased in many applications ranging from portable devices through electric vehicles to large-scale grid systems over the past decades. Yet, a more advanced ESS is required due to the safety issues and limited energy density of currently commercialized lithium-ion batteries (LIBs) for wide and matured applications. As a solution to this challenge, zinc-air batteries (ZABs) have gained tremendous attention due to their high energy density, low cost, environmental friendliness, and much lower fire risk characteristics. ZABs utilize oxygen from the atmosphere at their cathode during discharge, where the atmospheric oxygen is reduced to hydroxide via an oxygen reduction reaction (ORR). On the other hand, hydroxide is released as oxygen via oxygen evolution reaction (OER) during charge. The fact that oxygen is drawn directly from the air enables high gravimetric and volumetric energy densities of ZABs compared to those of commercial LIBs. However, the sluggish kinetics of the four-electron transfer steps in ORR and the mass transport of oxygen in OER remain major challenges for the practical application of ZABs. Meanwhile, precious metal-based catalysts such as Pt/C and RuO2 are known to have good catalytic activity towards ORR and OER. However, the integration of different catalysts into the same cathode is very difficult. Additionally, the high cost and natural scarcity of novel metals limit their usage for practical applications.We synthesized a bifunctional CoO/Mn3O4 heterostructure (CMH) OER/ORR electrocatalyst which was derived from metal-organic framework (MOF) for excellent activities in ZABs. The CMH cathode exhibited high ORR and OER performances, as demonstrated by the higher ORR current density than that of the Pt/C catalyst as well as the low OER overpotential exceeding those of the RuO2 catalyst. Remarkably, atomic structures of the CMH were elucidated using global optimization of genetic algorithm integrated with the machine learning force field. By adopting first-principles electronic structure calculations, we further revealed the charge transfer and active sites for both reactions in the identified heterojunction. Furthermore, assembling CMH cathode and Zn metal anode into a ZAB full-cell configuration achieves a ~5.5-fold higher energy density of 879 Wh kg-1 exceeding those of commercial lithium-ion batteries (LIBs), a high-discharge outstanding power density that is 1.39 times higher than novel metal catalysts, and robust cycle stability with negligible voltage decay which is far superior to that of benchmark Pt/C+RuO2 electrocatalysts.

Bursting and transforming MOF into n-type ZnO and p-type NiO based heterostructure for supercapacitive energy storage

Metal-organic frameworks (MOFs) have been considered as great contender and promising electrode materials for supercapacitors. However, their low capacity, aggregation, and poor porosity have necessitated the exploration of new approaches to enhance the performance of these active materials. In this study, sphere-like MOF were in-situ grown and it subsequently burst, transformed into a desired metal oxide heterostructure comprising n-type ZnO and p-type NiO (ZnO/NiO-350). The resulting optimized flower-like structure, composed of interlaced nanoflakes derived from MOFs, greatly improved the active sites, porosity, and functionality of the electrode materials. The ZnO/NiO-350 electrode exhibited superior electrochemical activities for supercapacitors, compared to the parent MOF, bare n-type, and p-type counterparts. The specific capacitance can reach to 543 ​F ​g−1 at a current density of 1 ​A ​g−1. Theoretical modeling and simulations were employed to gain insights into the atomic-scale properties of the materials. Furthermore, an assembled hybrid device using active carbon and ZnO/NiO-350 as electrodes demonstrated excellent energy density of 44 ​Wh kg−1 at a power density of 1.6 Kw kg−1. After 5000 cycles at 10 ​A ​g−1, the cycling stability remained excellent 80 % of the initial capacitance. Overall, such evaluation of unique electrode with superior properties may be useful for the next generation supercapacitor electrode.

Origin of the synergistic effects of bimetallic nanoparticles coupled with a metal oxide heterostructure for accelerating catalytic performance

AbstractPrecisely tuning bicomponent intimacy during reactions by traditional methods remains a formidable challenge in the fabrication of highly active and stable catalysts because of the difficulty in constructing well‐defined catalytic systems and the occurrence of agglomeration during assembly. To overcome these limitations, a PtRuPNiO@TiOx catalyst on a Ti plate was prepared by ultrasound‐assisted low‐voltage plasma electrolysis. This method involves the oxidation of pure Ti metal and co‐reduction of strong metals at 3000°C, followed by sonochemical ultrasonication under ambient conditions in an aqueous solution. The intimacy of the bimetals in PtRuPNiO@TiOx is tuned, and the metal nanoparticles are uniformly distributed on the porous titania coating via strong metal‒support interactions by leveraging the instantaneous high‐energy input from the plasma discharge and ultrasonic irradiation. The intimacy of PtRuPNiO@TiOx increases the electron density on the Pt surface. Consequently, the paired sites exhibit a high hydrogen evolution reaction activity (an overpotential of 220 mV at a current density of 10 mA cm−2 and Tafel slope of 186 mV dec−1), excellent activity in the hydrogenation of 4‐nitrophenol with a robust stability for up to 20 cycles, and the ability to contrast stated catalysts without ultrasonication and plasma electrolysis. This study facilitates industrially important reactions through synergistic chemical interactions.

Hierarchical NiGa2O4@C@CeO2 microstructure for sensitive and selective triethylamine gas sensing

Metal oxide heterostructures have been demonstrated excellent candidates acting as novel gas sensors with outstanding sensitivity and selectivity. In this work, a hierarchical NiGa2O4@C@CeO2 heterostructure with corn-like NiGa2O4 microcrystals covered by a thin carbon layer and then anchored with numerous amounts of external CeO2 nanoparticles was prepared through the combination of hydrothermal and a subsequent calcination method. The NiGa2O4@C@CeO2 composite demonstrates an excellent selective triethylamine (TEA) detection performance with a response of 11.1 towards 20 ppm TEA and a fast response/recovery time of 81 s/38 s. It also shows terrific selectivity for TEA when mixed with else interfering substances, along with prolonged reusability for at least 15 days. The enhanced TEA sensing performance can be ascribed to the significant improvement of conductivity and effective carrier transfer at the interface. This work provides a feasible method to fabricate metal oxide sensors with improved gas sensing performance.

Highly Sensitive Diethylamine Detection at Room Temperature Using g-C3N4 Nanosheets Decorated with CuO Hollow Polyhedral Structures.

Chemiresistive-based metal oxide semiconductor (MOS) gas sensors are widely used in gas sensing due to their advantageous properties. Graphitic carbon nitride (g-C3N4) and metal oxide heterostructure materials can improve charge transport properties, selectivity, and sensitivity in MOS gas sensor materials. Herein, for the first time, CuO hollow polyhedral structures (HPSs) were synthesized via a hydrothermal technique and annealed at different temperatures, with the 400 °C annealed (CuO-400 HPSs) demonstrating remarkable sensing capabilities for diethylamine (DEA) gas at room temperature (RT). The x-g-C3N4 nanosheets were decorated with CuO HPSs in varying amounts (x = 0.8, 1.8, 2.1, and 3.1 wt %) and then annealed at 400 °C for x-g-C3N4-CuO-400 hollow polyhedral heterostructures (HPHSs). Indeed, among the synthesized samples, the 1.8%-g-C3N4-CuO-400 HPHSs have a higher sensitivity to DEA (resistance change in gas (Rg) and air (Ra); Rg/Ra= 65 @ 20 ppm), a low detection limit (Rg/Ra= 6 @ 500 ppb), wide dynamic response (Rg/Ra= 190 @ 80 ppm), strong stability (30 days), and 21.6 times higher sensitivity than pure CuO at RT toward 20 ppm of DEA. The exceptional gas-sensing behavior can be attributed to various factors, including controlled annealing conditions that result in the formation of well-defined structures and greater porosity, efficient charge transfer properties resulting from an optimized ratio of g-C3N4 to CuO in HPHSs, an abundance of defects, unsaturated Cu sites, and synergistic effects. The study presents a universal strategy for generating sensitive and selective g-C3N4-based composite materials for low-temperature gas sensors.

BiVO4-Based Heterojunction Photocathode for High-Performance Photoelectrochemical Hydrogen Peroxide Production.

Photoelectrochemical (PEC) cells provide a promising solution for the synthesis of hydrogen peroxide (H2O2). Herein, an integrated photocathode of p-type BiVO4 (p-BVO) array with tetragonal zircon structure coupled with different metal oxide (MOx, M = Sn, Ti, Ni, and Zn) heterostructure and NiNC cocatalyst (p-BVO/MOx/NiNC) was synthesized for the PEC oxygen reduction reaction (ORR) in production of H2O2. The p-BVO/SnO2/NiNC array achieves the production rate 65.46 μmol L-1 h-1 of H2O2 with a Faraday efficiency (FE) of 76.12%. Combined with the H2O2 generation of water oxidation from the n-type Mo-doped BiVO4 (n-Mo:BVO) photoanode, the unbiased photoelectrochemical cell composed of a p-BVO/SnO2/NiNC photocathode and n-Mo:BVO photoanode achieves a total FE of 97.67% for H2O2 generation. The large area BiVO4-based tandem cell of 3 × 3 cm2 can reach a total H2O2 production yield of 338.84 μmol L-1. This work paves the way for the rational design and fabrication of artificial photosynthetic cells for the production of liquid solar fuel.

Effect of fabrication processes on BaTiO3 capacitor properties

There is an increasing desire to utilize complex functional electronic materials such as ferroelectrics in next-generation microelectronics. As new materials are considered or introduced in this capacity, an understanding of how we can process these materials into those devices must be developed. Here, the effect of different fabrication processes on the ferroelectric and related properties of prototypical metal oxide (SrRuO3)/ferroelectric (BaTiO3)/metal oxide (SrRuO3) heterostructures is explored. Two different types of etching processes are studied, namely, wet etching of the top SrRuO3 using a NaIO4 solution and dry etching using an Ar+-ion beam (i.e., ion milling). Polarization-electric-field hysteresis loops for capacitors produced using both methods are compared. For the ion-milling process, it is found that the Ar+ beam can introduce defects into the SrRuO3/BaTiO3/SrRuO3 devices and that the milling depth strongly influences the defect level and can induce a voltage imprint on the function. Realizing that such processing approaches may be necessary, work is performed to ameliorate the imprint of the hysteresis loops via ex situ “healing” of the process-induced defects by annealing the ferroelectric material in a barium-and-oxygen-rich environment via a chemical-vapor-deposition-style process. This work provides a pathway for the nanoscale fabrication of these candidate materials for next-generation memory and logic applications.

Engineering metal oxide heterostructures derived from MOFs/MXene hybrids as efficient acetone sensor

Acetone, one of the most used solvents in industry and the laboratory, can anesthetize the central nervous system of humans and cause damage to the kidneys, pancreas, and liver. For the purpose of monitoring the leakage and concentration of acetone, α-/γ-Fe2O3/TiO2-X (α-/γ-Fe2O3-X) materials were successfully manufactured by in-situ solvothermal and calcination processes. Here, MIL-100-derived porous α-/γ-Fe2O3 and TiO2 nanoparticles are uniformly grown on the self-sacrificial template of exfoliated Ti3C2Tx nanosheets (ex-Ti3C2Tx) that simultaneously serve as the Ti source. The heterostructure between TiO2 and Fe2O3 therein is conducive to carrier transfer and sharp resistance change. And bulk resistance-controlled γ-Fe2O3 is able to raise the response to gas. Besides, the porous structure of α-/γ-Fe2O3-X could create plenty of oxygen vacancies and surface functional groups, which facilitate diffusion and contact interaction between acetone and active sites. Accordingly, the α-/γ-Fe2O3-X endow exceptional response (R = 105.5) towards 100 ppm acetone at 240 ℃, fast response/recovery time, outstanding selectivity and stability. To further substantiate this promotion mechanism, density functional theory (DFT) calculations were carried out for investigating the adsorption behavior of α-/γ-Fe2O3-X for acetone.

Construction of SnO2/SnS2 n-n heterojunction anchored on rGO for synergistically enhanced low temperature formaldehyde sensing performance

Creating metal oxide heterostructures is a promising way to enhance sensing performance by modulating their electronic properties. Herein, SnO2/SnS2 n-n heterojunction anchored on rGO (3.84 % of SnS2) was constructed using a hydrothermal route and fabricated as sensors for detecting formaldehyde (HCHO). The response value of the SnO2/SnS2/rGO sensor is 8.91 to 10 ppm HCHO (100 °C), which is about 2.6 and 1.8 times higher than that of the SnO2 and SnO2/SnS2 sensor (200 °C), respectively. The SnO2/SnS2/rGO sensor is also sensitive to ppb level HCHO (1.33 to 100 ppb), exhibits fast response/recovery speed, good reproducibility and long-term stability, and remarkable selectivity. The significant enhancement performance of the SnO2/SnS2/rGO sensor could be ascribed to the synergistic effect of the n-n heterojunction between SnO2 and SnS2, as well as the presence of rGO, which acts as a charge carrier facilitator and enhances the specific surface area boost the high sensing properties. This work provides a practical approach to synthesizing hybrid materials with adjustable micro-morphology, and a promising strategy for designing HCHO sensors with high sensing performance.

Synergistic atom co-sharing and S-scheme heterojunction: constructing Cu/CuO/Cu2O with ultrathin graphene-like carbon derived from basil seeds for enhanced photo-oxidation of benzyl alcohols to aldehydes.

This study is centered on the oxidative transformation of alcohols into their respective aldehyde compounds, employing an S-scheme heterostructure featuring CuO/Cu2O on graphene-like carbon (GLC) derived from a basil seed hydrogel. Experimental characterization and theoretical calculations highlight that the implementation of S-scheme heterostructures achieves not only enhanced charge-separation efficiency, facilitated by the interfacial built-in electric field, Cu co-sharing at the CuO/Cu2O interface, and electron carrier activity of the GLC support, but also maintains a strong driving force for photocatalytic organic conversion. The resulting nanocomposites play a crucial role in transferring and reducing the recombination of photoexcited charge carriers, preserving the oxidizability of CuO holes and the reducibility of Cu2O electrons. Through meticulous adjustment of precursor amounts, the CuO-Cu2O/GLC heterojunction exhibited the highest photocurrent at 6.83 mA cm-2, demonstrating optimal performance in the photocatalytic selective oxidation of benzyl alcohol with an average conversion rate of 95.0%. Furthermore, the stability of CuO-Cu2O/GLC was thoroughly investigated, revealing sustained high conversion even after five repeated experiments, underscoring its potential for practical applications. The study also proposes a plausible mechanism for the transformation of benzyl alcohol into benzaldehyde through capture experiments of active species. Importantly, this research introduces a straightforward in situ hydrothermal growth protocol for efficiently constructing metal oxide heterostructures wrapped in an rGO support. It provides valuable insights into designing new synthetic strategies for preparing efficient photocatalysts and hints at the development of novel, efficient, and practical photocatalytic systems.

Modulated transport and magnetic behavior in antiferromagnetic NdNiO3/SrIrO3 bilayers

Antiferromagnetic spintronics is intrigued due to its unique properties that could break through the restrictions in ferromagnets. A 3d/5d transition metal oxide heterostructure is a good platform in antiferromagnetic spintronics research since the strong spin–orbit coupling in 5d oxides may bring about delicate interaction with the correlation energy and motivate unconventional phenomena. Here, the transport and magnetic characters of bilayers composed of antiferromagnetic 3d perovskite NdNiO3 and 5d perovskite SrIrO3 were investigated. The decreased metal–insulator transition and Néel temperature associated with suppressed negative magnetoresistance, emerged spin-glass like phenomenon, and the humped nonlinear Hall effect were observed in NdNiO3/SrIrO3 bilayers, which were absent in NdNiO3 and SrIrO3 pure films. It suggests the important role of interfacial interaction between NdNiO3 and SrIrO3 in modulating heterostructure transport and magnetic behavior and also manifests that complex magnetic structures might be realized in NdNiO3/SrIrO3 bilayers.

(Invited) Role of Heterojunctions in Metal Oxide Heterostructures for Energy and Environmental Applications

Heterostructures made from metal oxide semiconductors are fundamental for the development of high-performance gas sensors and electrocatalysts, for examples. Here, I will introduce hierarchical heterostructures composed of p-, n-type and insulating metal oxide shells.Precisely controlled films of alternating metal oxides can be uniformly deposited onto the inner and outer walls of the CNTs and onto mesoporous substrates by atomic layer deposition. The morphological, microstructural and electrical characteristics of the heterostructures were thoroughly investigated. Electrical resistance measurements highlighted the large influence of the metal oxides thickness and charge carriers types, suggesting that the conductivity of the electrodes are dominated by Schottky barrier junctions across the heterojunctions.The behavior of the heterostructured electrodes in sensors and in electrocatalysis applications was investigated for low concentrations of volatile organic compounds and pollutants, and the oxygen evolution reaction in acidic media, respectively. For examples, the gas sensing response of the heterostructures showed a strong dependence on the thickness of the metal oxide shell layers and the type of heterostructures formed. On the other hand, the electrocatalytic performances are strongly related to the surface catalyst/stabilization layer and the electrical conductivity of the heterostructured electrode.On the basis of the morphological, microstructural and electrical characterization, and electrode performances, the mechanisms which account for the performances of our heterostructured electrodes will be correlated and discussed.

Metal-Oxide Heterojunction: From Material Process to Neuromorphic Applications.

As technologies like the Internet, artificial intelligence, and big data evolve at a rapid pace, computer architecture is transitioning from compute-intensive to memory-intensive. However, traditional von Neumann architectures encounter bottlenecks in addressing modern computational challenges. The emulation of the behaviors of a synapse at the device level by ionic/electronic devices has shown promising potential in future neural-inspired and compact artificial intelligence systems. To address these issues, this review thoroughly investigates the recent progress in metal-oxide heterostructures for neuromorphic applications. These heterostructures not only offer low power consumption and high stability but also possess optimized electrical characteristics via interface engineering. The paper first outlines various synthesis methods for metal oxides and then summarizes the neuromorphic devices using these materials and their heterostructures. More importantly, we review the emerging multifunctional applications, including neuromorphic vision, touch, and pain systems. Finally, we summarize the future prospects of neuromorphic devices with metal-oxide heterostructures and list the current challenges while offering potential solutions. This review provides insights into the design and construction of metal-oxide devices and their applications for neuromorphic systems.

Plasma-Induced 2D Electron Transport at Hetero-Phase Titanium Oxide Interface.

Interfaces of metal oxide heterojunctions display a variety of intriguing physical properties that enable novel applications in spintronics, quantum information, neuromorphic computing, and high-temperature superconductivity. One such LaAlO3 /SrTiO3 (LAO/STO) heterojunction hosts a 2D electron liquid (2DEL) presenting remarkable 2D superconductivity and magnetism. However, these remarkable properties emerge only at very low temperatures, while the heterostructure fabrication is challenging even at the laboratory scale, thus impeding practical applications. Here, a novel plasma-enabled fabrication concept is presented to develop the TiO2 /Ti3 O4 hetero-phase bilayer with a 2DEL that exhibits features of a weakly localized Fermi liquid even at room temperature. The hetero-phase bilayer is fabricated by applying a rapid plasma-induced phase transition that transforms a specific portion of anatase TiO2 thin film into vacancy-prone Ti3 O4 in seconds. The underlying mechanism relies on the screening effect of the achieved high-density electron liquid that suppresses the electron-phonon interactions. The achieved "adiabatic" electron transport in the hetero-phase bilayer offers strong potential for low-loss electric or plasmonic circuits and hot electron harvesting and utilization. These findings open new horizons for fabricating diverse multifunctional metal oxide heterostructures as an innovative platform for emerging clean energy, integrated photonics, spintronics, and quantum information technologies.

Epitaxial growth of Co3O4/In2O3 p-n heterostructure with rich oxygen vacancies for ultrahigh triethylamine sensing

Although metal oxides based gas sensors have been researched extensively in previous works, there are enormous challenges on improving the deficiencies in poor selectivity, sensitivity, humidity resistance and so on. Hence, we developed an epitaxial growth method to prepare dendritic Co3O4/In2O3-(1−3) heterostructures of distinct Co/In mass ratios through perfect lattice matching between the two crystal domains at the interface, along with introducing large amounts of oxygen vacancies. As a result, the Co3O4/In2O3-2 heterostructure based gas sensor showed enhanced sensing properties towards triethylamine (TEA, 100 ppm) with a high response value of Ra/Rg = 576.1 at an optimal working temperature of 200 °C, which is 93 times higher than that of pristine In2O3. Moreover, the Co3O4/In2O3-2 sensor exhibited excellent gas selectivity, quick recovery time, repeatable cycling, long-term stability, as well as outstanding humidity resistance. The improved TEA gas sensing performance can be attributed to the integration of interfacial synergies in Co3O4/In2O3 p-n heterostructure and generation of rich oxygen vacancies, exposing more active sites to facilitate the adsorption/desorption of gas molecules. This work provides a feasible pathway to regulate TEA sensing performance of metal oxide semiconductor (MOS) gas sensors by capitalizing on self-sacrificial template strategy and reconstruction of novel metal oxide heterostructure.

Atomic layer deposition of SnO2 on In2O3 enables ultrasensitive NO2 detection at room temperature and DFT mechanism research

The unique electronic and chemical properties of metal oxide heterostructures are critical to the development of room temperature (RT) sensors. In this work, we report the design of In2O3/SnO2 heterostructures based on atomic layer deposition (ALD), which regulates the energy band structure of the material and promotes the electron transfer, thus enhancing the adsorption of target gases. The sensor based on In2O3/SnO2 demonstrates outstanding sensing performance at RT with an extreme response of 2900 to 10 ppm NO2, which to our knowledge outperforms the reported metal oxide sensors, as well as a detection limit of 61 ppb. Density functional theory (DFT) calculations show that the charge transfer (0.494 e) and interaction energy (2.19 eV) between In2O3/SnO2 and NO2 are significantly enhanced. This work highlights the critical function of heterostructured materials in enhancing the sensing capabilities of semiconductors, providing some hints for the design of ultrasensitive NO2 sensors.

Synergistic Active Phases of Transition Metal Oxide Heterostructures for Highly Efficient Ammonia Electrosynthesis

AbstractElectrochemically converting waste nitrate (NO3−) into ammonia (NH3) is a green route for both wastewater treatment and high‐value‐added ammonia generation. However, the NO3−‐to‐NH3 reaction involves multistep electron transfer and complex intermediates, making it a grand challenge to drive efficient NO3− electroreduction with high NH3 selectivity. Herein, an in‐operando electrochemically synthesized Cu2O/NiO heterostructure electrocatalyst is proven for efficient NH3 electrosynthesis. In situ Raman spectroscopy reveals that the obtained Cu2O/NiO, induced by the electrochemistry‐driven phase conversion, is the real active phase. This electronically coupled phase can modulate the interfacial charge distribution, dramatically lower the overpotential in the rate‐determining step and thus requiring lower energy input to proceed with the NH3 electrosynthesis. The orbital hybridization calculations further identify that Cu2O is beneficial for NO3− adsorption, and NiO could promote the desorption of NH3, forming an excellent tandem electrocatalyst. Such a tandem system leads to NH3 Faradaic efficiency of 95.6%, a super‐high NH3 selectivity of 88.5% at −0.2 V versus RHE, surpassing most of the NH3 electrosynthesis catalysts at an ultralow reaction voltage.

Modifying charge transfer between rhodium and ceria for boosted hydrogen oxidation reaction in alkaline electrolyte

Sluggish kinetics of hydrogen oxidation reaction (HOR) in alkaline solution has restricted the rapid development of hydrogen economy. Constructing catalyst with metal-oxide heterostructures can enhance HOR performance; however, little studies concentrate on charge transfer between them, and the corresponding effects on reactions remain unclear. Herein, we report charge-transfer-adjustable CeO2/Rh interfaces uniformly dispersed on multiwalled carbon nanotube (CNT), which exhibit excellent alkaline HOR performance. Results confirm that the charge transfer from Rh to CeO2 could be conveniently tuned via thermal treatment. Consequently, the adsorption free energies of H* in Rh sites and OH* adsorption strength in CeO2 could be adjusted, as corroborated by density functional theory study. The optimized CeO2/Rh interfaces exhibit an exchange current density and a mass-specific kinetic current of 0.53 mA cmPGM−2 and 830 A gPGM−1 at an overpotential of 50 mV, respectively, which surpasses most of the advanced noble-metal-based electrocatalysts. This work provides a new insight of harnessing charge transfer of heterostructure to enhance catalytic activities.

Engineering sensitive gas sensor based on MOF-derived hollow metal-oxide semiconductor heterostructures

Metal-organic frameworks (MOFs) derived hollow heterostructured metal oxide semiconductors (MOSs) are a class of functional porous materials exhibiting distinctive physiochemical properties. Owing to the unique advantages, including large specific surface, high intrinsic catalytic performance, abundant channels for facilitating electron transfer and mass transport, and strong synergistic effect between different components, MOF-derived hollow MOSs heterostructures can work as promising candidates for gas sensing, which have thus attracted increasing attention. Aiming to provide a deep understanding on the design strategy and MOSs heterostructure, this review presents a comprehensive overview on the advantages and applications of MOF-derived hollow MOSs heterostructures when they used n for the detection of toxic gases. In addition, a deep discussion about the perspective and challenge of this interesting field is also well organized, hoping to provide guidance for the future design and development of more accurate gas sensors.