Interplay between Molybdenum Dopant and Oxygen Vacancies in a TiO2 Support Enhances the Oxygen Reduction Reaction

Alkaline liquid-derived NaxTi11.5MoVOx/C-40 material with controlled electron transfer rate for sensitive electrochemical detection of dopamine

The neurotransmitter dopamine (DA) is associated with many physiological and pathological processes, so the importance of low detection limits and high sensitivity analysis cannot be overstated, especially for early disease detection. Here, 2 M NaOH aqueous solution is used to precipitate metal ions in an ethanol solution containing carbon black (CB), and then nanocomposite catalysts (NaxTi11.5MoVOx/C-40 (40 denoted as 40 mg CB)) were obtained by calcining the precipitation. When used for DA detection, NaxVOx acts as the main active site for electrochemical oxidation of DA and NaxTi11.5MoOx plays a role in facilitating the binding of DA to the active site and stabilizing the active site. The NaxTi11.5MoVOx/C-40 electrochemical biosensor has a limit of detection (LOD) of 0.003 μM with a linear range of 0.005-51.665 μM for DA. This sensor can be used to sensitively identify the concentration of DA in human blood and urine. Catalysts containing varying amounts of CB exhibit diverse electron transfer rates, and surprisingly, we found that the appropriate electron transfer rate is optimal for the detection of low concentrations of DA. Because the performance of the electrochemical biosensors is affected by both the activity of the catalysts and the accuracy of the electrochemical testing instrumentation. To better explain this phenomenon, we propose the concept of resolution (Rn) and present the formula to derive it, offering a new approach to evaluating the performance of electrochemical biosensors.

Oxygen vacancy induced interaction between Pt and TiO2 to improve the oxygen reduction performance

In proton exchange membrane fuel cells (PEMFCS), a Pt-based catalyst has been plagued by activity and durability, making it difficult to implement in large-scale commercial applications. In this paper, a composite material formed by titanium dioxide and carbon black containing oxygen vacancies (TiO2(OV)-C) was used as a functional support to successfully load Pt nanoparticles (NPS). The introduction of oxygen vacancies induces the formation of a connection between Pt and TiO2, which not only strengthens the fixation of Pt by the composite support but also optimizes the local charge density of Pt. Compared with Pt/C (0.842 V) and Pt/TiO2-C (0.841 V), the half-wave potential (E1/2) of Pt/TiO2(OV)-C (0.862 V) is increased by 20 mV and 21 mV, respectively. After a long-term durability test, the E1/2 of Pt/TiO2(OV)-C is only attenuated by 5 mV. In addition, the mass activity (MA) and specific activity (SA) decreased from 183.4 mA mg-1 and 0.565 mA cm-2 to 144.4 mA mg-1 and 0.483 mA cm-2 at 0.85 V, only decreasing by 21% and 17 %, showing good stability. X-ray photoelectron spectroscopies (XPS) and density functional theory (DFT) calculations show that the interaction between Pt and TiO2 reduces the d-band center of Pt, thereby improving the desorption of intermediates *OH, which in turn promotes the activity of alkaline ORR. This study not only shows that OV plays a key role in the process of inducing interaction, but also deeply studies the influence of this interaction on the active site Pt, which provides more choices for the design of excellent multiphase catalysts.

Synergistic material modification-induced optimization of interfacial charge transfer and surface hydrogen adsorption

Being chemically stable, low cost and made from abundant resources, titanium dioxide (TiO2) possesses the most desired advantages for photocatalytic applications. However, the intrinsic limits of high surface hydrogen adsorption energy, wide band gap, low separation rate and rapid recombination of the photogenerated charge carriers greatly hamper its utilization. To address these issues, the present work combines density functional theory (DFT) calculations with rational modifications of TiO2 with nickel doping and an ultra-thin shield of fluorinated carbon (FNT) for application in the photocatalytic hydrogen evolution reaction (HER). Comprehensive studies imply that the synergistic modifications not only optimize the surface H adsorption, but also facilitate the interfacial charge transfer and simultaneously prevent the photochemical and chemical corrosion of the catalysts. In good agreement with the theoretical predictions, the resulting FNT photocatalysts demonstrate an optimal HER efficiency of 13.0 mmol g-1 h-1, nearly 33-times and over three-times beyond that of the pristine TiO2 (0.4 mmol g-1 h-1) and the Ni-doped TiO2 (4.2 mmol g-1 h-1), respectively. Moreover, the composite also exhibits excellent stability with a well-reproducible HER performance over a 66-hour cyclic HER test of 15 cycles.

Combined effects of Pt nanoparticles and oxygen vacancies to promote photothermal catalytic degradation of toluene

Pt/Mn-TiO₂ photothermal catalysts with abundant oxygen vacancies are prepared by loading Pt onto a composite of MnO_x and TiO₂ using MIL-125 as precursor (abbreviated as Mn-TiO₂) and subsequent hydrogen reduction treatment. Under light irradiation with intensity of 625 mW/cm², the optimal 0.65Pt/Mn-TiO₂ catalyst can achieve toluene conversion of 90.4 % and CO₂ yield of 85.6 %, respectively, and maintain stable activity for at least 30 h in the presence of coke and water. The introduction of Pt nanoparticles improves the utilization of solar spectrum and facilitates the generation of more oxygen vacancies. The comparative experiments of photothermal catalysis and thermal catalysis further verify that light not only acts as a heat source but also enhances catalytic reaction through photocatalysis and photoactivation of lattice oxygen. In the follow-up work, catalytic oxidation under natural sunlight is performed on 0.65Pt/Mn-TiO₂ to reach 75.0 % of toluene conversion, displaying a good practical application potential.

Metal Oxide-Supported Metal Catalysts for Electrocatalytic Oxygen Reduction Reaction: Characterization Methods, Modulation Strategies, and Recent Progress

The sluggish kinetics of the oxygen reduction reaction (ORR) with complex multielectron transfer steps significantly limits the large-scale application of electrochemical energy devices, including metal-air batteries and fuel cells. Recent years witnessed the development of metal oxide-supported metal catalysts (MOSMCs), covering single atoms, clusters, and nanoparticles. As alternatives to conventional carbon-dispersed metal catalysts, MOSMCs are gaining increasing interest due to their unique electronic configuration and potentially high corrosion resistance. By engineering the metal oxide substrate, supported metal, and their interactions, MOSMCs can be facilely modulated. Significant progress has been made in advancing MOSMCs for ORR, and their further development warrants advanced characterization methods to better understand MOSMCs and precise modulation strategies to boost their functionalities. In this regard, a comprehensive review of MOSMCs for ORR is still lacking despite this fast-developing field. To eliminate this gap, advanced characterization methods are introduced for clarifying MOSMCs experimentally and theoretically, discuss critical methods of boosting their intrinsic activities and number of active sites, and systematically overview the status of MOSMCs based on different metal oxide substrates for ORR. By conveying methods, research status, critical challenges, and perspectives, this review will rationally promote the design of MOSMCs for electrochemical energy devices.

Untangling product selectivity on clean low index rutile TiO2 surfaces using first-principles calculations

Computational modeling of metal oxide surfaces provides an important tool to help untangle complex spectroscopy and measured catalytic reactivity. There are many material properties that make rational catalytic design challenging, and computational methods provide a way to evaluate possible structural factors, like surface structure, individually. The mechanism of water oxidation or oxygen evolution is well studied on some anatase surfaces and the rutile TiO₂ (110) surface but has not yet been mapped on other low-index Miller rutile surfaces that are present in most experimental nano-titania catalysts. Here first principles calculations provide new insights into water oxidation mechanisms and reactivity of the most common low-index Miller facets of rutile TiO₂. The reactivity of three surfaces, (101), (010), and (001), are explored for the first time and the product selectivity of multistep electron transfer on each surface is compared to the well-studied (110) surface. Density functional theory shows that a peroxo, O^(p), intermediate is more favorable for water oxidation on all facets. The ˙OH radical formation is favored on the (001) facet resulting in a high overpotential for oxygen evolution reaction (OER). The (101) and (110) facets have low overpotentials, ∼0.3 V, and favor two-electron proton-coupled electron transfer to produce H₂O₂. The only facet that prefers direct OER is (001), leading to O₂ evolution in a four-electron process with an overpotential of 0.53 V. A volcano plot predicts the selectivity and activity of low-index Miller facets of rutile TiO₂, revealing the high activity of the peroxo OER mechanism on the (010) facet.

Adsorption Energy in Oxygen Electrocatalysis

Adsorption energy (AE) of reactive intermediate is currently the most important descriptor for electrochemical reactions (e.g., water electrolysis, hydrogen fuel cell, electrochemical nitrogen fixation, electrochemical carbon dioxide reduction, etc.), which can bridge the gap between catalyst's structure and activity. Tracing the history and evolution of AE can help to understand electrocatalysis and design optimal electrocatalysts. Focusing on oxygen electrocatalysis, this review aims to provide a comprehensive introduction on how AE is selected as the activity descriptor, the intrinsic and empirical relationships related to AE, how AE links the structure and electrocatalytic performance, the approaches to obtain AE, the strategies to improve catalytic activity by modulating AE, the extrinsic influences on AE from the environment, and the methods in circumventing linear scaling relations of AE. An outlook is provided at the end with emphasis on possible future investigation related to the obstacles existing between adsorption energy and electrocatalytic performance.

Fe Ions-Doped TiO2 Aerogels as Catalysts of Oxygen Reduction Reactions in Alkaline Solutions

Aerogels have interconnected networks and preeminent pore structures. When used as the catalysts for oxygen reduction reaction (ORR), they can facilitate the mass transfer and expose more active sites. Here, we synthesized the Fe-doped titanium oxide-based aerogels (TA/Fes) by the sol-gel method combined with thermal treatment. The specific surface areas of the TA/Fes ranged from 475 to 774 m²·g^-1, and the pore volumes varied from 0.96 to 1.72 cm³·g^-1. The doping effect of the Fe ions and the oxygen vacancies in anatase enhance the electrical conductivity, leading to the low Rct (313.3-828.2 Ω). All samples showed excellent stability (2.0-4.5 mV) and 4e^- pathway. The limiting current density of TA/Fe3 reached 5.34 mA·cm^-2, which was comparable to that of commercial Pt/C. The preparation method is inspiring and the as-prepared aerogel catalysts have potential in promoting the scale of fuel cells.

Efficient H2 Evolution Coupled with Anodic Oxidation of Iodide over Defective Carbon-Supported Single-Atom Mo-N4 Electrocatalyst

We successfully prepared nitrogen-doped defective carbon spheres (Mo-N₄/d-C) with a high loading of 0.996 wt % via a designed vapor-deposition process for IOR-based hydrogen generation. The synthesized Mo-N₄/d-C catalyst provides a record current density of 10 mA cm^-2 at 0.77 V. Further, the Mo-N₄/d-C catalyst shows a Tafel slope of 25.58 mV dec^-1, exceptional stability over time in acidic media, a higher hydrogen generation rate of 0.1063 mL g_cat^-1 min^-1, a high Faradaic efficiency of 99.8%, and a reduction of the energy consumption up to ∼50% for hydrogen evolution by anodic oxidation reaction of iodide (IOR) compared with the conventional OER-based electrolysis. Computational calculations demonstrate that the Mo-N₄/d-C structure plays a vital effect on the activity of iodide oxidation, which is competitive with the Pt catalyst.

A review on TiO2-x-based materials for photocatalytic CO2 reduction

Photocatalytic CO₂ reduction technology has a broad potential for dealing with the issues of energy shortage and global warming. As a widely studied material used in the photocatalytic process, titanium dioxide (TiO₂) has been continuously modified and tailored for more desirable application. Recently, the defective/reduced titanium dioxide (TiO_2-x) catalyst has attracted broad attention due to its excellent photocatalytic performance for CO₂ reduction. In this perspective review, we comprehensively present the recent progress in TiO_2-x-based materials for photocatalytic CO₂ reduction. In detail, the review starts with the fundamentals of CO₂ photocatalytic reduction. Then, the synthesis of a defective TiO₂ structure is introduced for the regulation of its photocatalytic performance, especially its optical properties and dissociative adsorption properties. In addition, the current application of TiO_2-x-based photocatalysts for CO₂ reduction is also highlighted, such as metal-TiO_2-x, oxide-TiO_2-x and TiO_2-x-carbon-based photocatalysts. Finally, the existing challenges and possible scope of photocatalytic CO₂ reduction over TiO_2-x-based materials are discussed. We hope that this review can provide an effective reference for the development of more efficient and reasonable photocatalysts based on TiO_2-x.

Improved the Methanol Electro-Oxidation and Carbon Monoxide Tolerance for Direct Methanol Fuel Cells Using Strontium Molybdate

A high methanol electro-oxidation (MOR) and carbon monoxide (CO) tolerance satisfied the electrochemical requirements of direct methanol fuel cells (DMFCs). The study investigated strontium molybdate (SrMoO4) mixed with Vulcan XC-72, carbon-loaded with 20% Pt. The electrochemical performance was confirmed by MOR and CO tolerance activities measured via cyclic voltammetry (CV). The synergistic effect between Pt and SrMoO4 is essential to affect the electrochemical characteristic. SrMoO4 can help remove CO-like intermediate products on the Pt surface, enhancing electrochemical performance for DMFCs. In addition, HxMoO3/HyMoO3 existence in Sr0.5Mo0.5O4−δ can quickly remove intermediates from Pt surfaces and accelerate the transformation of adsorbed intermediates to CO2. The results obtained showed that 20%-Pt/uncalcined Sr0.5Mo0.5O4−δ-C electrocatalyst has higher MOR and CO tolerance ability in DMFCs. Furthermore, the fabricated DMFC shows excellent long-term electrochemical stability after 1000 cycles and a maximum power density (1.42 mW/cm2) higher than commercial 20%-Pt/C (1.27 mW/cm2).

Microwave-Assisted Solvothermal Synthesis of Mo-Doped TiO2 with Exceptional Textural Properties and Superior Adsorption Kinetics

Assigned to their outstanding physicochemical properties, TiO₂-based materials have been studied in various applications. Herein, TiO₂ doped with different Mo contents (Mo-TiO₂) was synthesized via a microwave-assisted solvothermal approach. This was achieved using titanium (IV) butoxide and molybdenum (III) chloride as a precursor and dodecylamine as a surface directing agent. The uniform effective heating delivered by microwave heating reduced the reaction time to less than 30 min, representing several orders of magnitude lower than conventional heating methods. The average particle size ranged between 9.7 and 27.5 nm and it decreased with increasing the Mo content. Furthermore, Mo-TiO₂ revealed mesoporous architectures with a high surface area ranging between 170 and 260 m² g⁻¹, which is superior compared to previously reported Mo-doped TiO₂. The performance of Mo-TiO₂ was evaluated towards the adsorption of Rhodamine B (RhB). In contrast to TiO₂, which revealed negligible adsorption for RhB, Mo-doped samples depicted rapid adsorption for RhB, with a rate that increased with the increase in Mo content. Additionally, Mo-TiO₂ expressed enhanced adsorption kinetics for RhB compared to state-of-the-art adsorbents. The introduced synthesis procedure holds a grand promise for the versatile synthesis of metal-doped TiO₂ nanostructures with outstanding physicochemical properties.

Anchoring Highly Dispersed Pt Electrocatalysts on TiOx with Strong Metal-Support Interactions via an Oxygen Vacancy-Assisted Strategy as Durable Catalysts for the Oxygen Reduction Reaction

Pt electrocatalysts with high activity and durability have still crucial issues for the oxygen reduction reaction (ORR) in proton exchange membrane fuel cells (PEMFCs). In this study, a novel catalyst consisting of Pt nanoparticles (NPs) on TiO_x/C composites (TiO_x-V_o-H/C) with abundant oxygen vacancies (V_o) is proposed, which is abbreviated as PTO-V_o-H/C. The introduction of V_o helps anchor highly dispersed Pt NPs with low loading and strengthen the strong metal-support interaction (SMSI), which benefits to the enhanced ORR catalytic activity. Moreover, the accelerated durability test (ADT) demonstrates the higher retention of ORR activity for PTO-V_o-H/C. Experimental and theoretical analyses reveal that electronic interactions between Pt NPs and TiO_x/C composite support give rise to an electron-rich Pt NPs and strong SMSI effect, which is favorable for the electron transfer and stabilization of Pt NPs. More importantly, the assembled PEMFC with PTO-V_o-H/C shows only 6.9% of decay on maximum power density after 3000 ADT cycles while the performance of Pt/C sharply decreased. This work provides a new insight into the unique vacancy regulation of dispersive Pt on metal oxides for superior ORR performance.

Noble Metal-Based Multimetallic Nanoparticles for Electrocatalytic Applications

Noble metal-based multimetallic nanoparticles (NMMNs) have attracted great attention for their multifunctional and synergistic effects, which offer numerous catalytic applications. Combined experimental and theoretical studies have enabled formulation of various design principles for tuning the electrocatalytic performance through controlling size, composition, morphology, and crystal structure of the nanoparticles. Despite significant advancements in the field, the chemical synthesis of NMMNs with ideal characteristics for catalysis, including high activity, stability, product-selectivity, and scalability is still challenging. This review provides an overview on structure-based classification and the general synthesis of NMMN electrocatalysts. Furthermore, postsynthetic treatments, such as the removal of surfactants to optimize the activity, and utilization of NMMNs onto suitable support for practical electrocatalytic applications are highlighted. In the end, future direction and challenges associated with the electrocatalysis of NMMNs are covered.

Electrochemically synthesized SnO2 with tunable oxygen vacancies for efficient electrocatalytic nitrogen fixation

Electrochemical nitrogen reduction reaction (NRR) driven by a renewable energy source offers a sustainable and environmentally benign route to produce ammonia (NH₃), but it is highly dependent on efficient and specific catalysts to reduce the high reaction barrier and improve the selectivity. Defect engineering is extensively used to regulate the surface properties of materials to improve their catalytic performance. Herein we synthesized SnO₂ with different oxygen vacancy concentrations by a controllable electrochemical method for electrocatalytic nitrogen (N₂) fixation. The prepared SnO₂ was used as an electrocatalyst and exhibited excellent NRR performance with an optimal NH₃ yield rate of 25.27 μg h^-1 mg_cat.^-1 and faradaic efficiency of 11.48% at -0.6 V (vs. the reversible hydrogen electrode) in 0.1 M Na₂SO₄. Oxygen vacancies provide more active sites and greater electron transfer ability on the catalyst surface to facilitate N₂ adsorption and activation. The electrocatalytic NRR performance of SnO₂ was enhanced with the increase in oxygen vacancy concentration. The density functional theory calculations indicate that the oxygen vacancies in SnO₂ promote the electrocatalytic NRR performance by increasing the number of valence electrons of Sn and decreasing the energy barrier of the potential-determining step, thus promoting the activation of the N-N bond to further achieve efficient N₂ fixation.

Oxygen vacancy-rich N-doped carbon encapsulated BiOCl-CNTs heterostructures as robust electrocatalyst synergistically promote oxygen reduction and Zn-air batteries

The development of non-precious metal catalysts for oxygen reduction reactions (ORR) is vital for promising clean energy technologies such as fuel cells, and zinc-air batteries. Herein, we present a stepwise synthesis of N-doped and carbon encapsulated BiOCl-CNTs heterostructures. Electrocatalytic ORR studies show that the optimized catalyst has a high half-wave potential (E_1/2) of 0.85 V (vs. RHE), large limiting current density (-5.34 mA cm^-2@0.6 V) in alkaline medium, and nearly perfect 4e^- reduction characteristics, even surpassing commercial Pt/C. Meanwhile, the catalyst has exceptional durability (above 97.5 % after 40000 s) and strong resistance towards methanol poisoning. The good ORR activity also results in high-performance zinc-air batteries with a specific capacity (724 mAh g^-1@10 mA cm^-2), a high open-circuit potential of 1.51 V and a peak power density of 170.7 mW cm^-2, as well as an ultra-long charge-discharge cycle stability (155 h), comparable with the Pt/C catalyst. The catalytic mechanism reveals that the excellent electrocatalytic performance originates from the synergistic effect of N doping, oxygen vacancies, and BiOCl sites.

Oxygen and Titanium Vacancies in a BiOBr/MXene-Ti3C2 Composite for Boosting Photocatalytic N2 Fixation

Solar energy can be used as "green" energy by photocatalysis for the nitrogen fixation under the atmospheric conditions compared with the traditional energy-intensive industrial production of ammonia. However, the complex kinetics and high reaction barriers greatly hinder the development of the photocatalytic N₂ reduction reaction. Herein, a BiOBr/MXene-Ti₃C₂ composite catalyst is prepared by the simple electrostatic adsorption and self-assembly method. The as-prepared 10 wt % BiOBr/Ti₃C₂ exhibits the best performance for N₂ fixation to NH₃ by photocatalysis. The evolution rate of NH₃ is up to 234.6 μmol·g^-1·h^-1, which is approximately 48.8 times and 52.4 times higher than those of pure BiOBr and Ti₃C₂, respectively. It is found that the designed double vacancies of oxygen and titanium for BiOBr/Ti₃C₂ composites, with the availability of localized electrons, have the ability to adsorb and activate N₂, which can be efficiently reduced to NH₃ by the interfacial electrons transferred from the excited BiOBr/Ti₃C₂ composite. In addition, the results of in situ Fourier transform infrared show the generation of N_xH_y species by the continuous protonation processes. Moreover, titanium vacancy (V_Ti) induces a strong absorption energy for nitrogen atoms on the surface of BiOBr/Ti₃C₂ according to the density functional theory calculations. In particular, the P-electron feedback caused by V_Ti could effectively promote the weakening of the N≡N triple bond and elongate the N₂ bond length by ∼31.6%. This work might provide new insights into the synergistic effect of double defects and inspiration for the rational design of catalysts by defect engineering in the field of catalytic synthesis of ammonia.

Self-Driven Reactive Oxygen Species Generation via Interfacial Oxygen Vacancies on Carbon-Coated TiO2-x with Versatile Applications

The effective activation and utilization of O₂ have always been the focus of scientists because of its wide applications in catalysis, organic synthesis, life and medical science. Here, a novel method for activating O₂ spontaneously via interfacial oxygen vacancies on carbon-coated TiO_2-x to generate reactive oxygen species (ROS) with versatile applications is reported. The interfacial oxygen vacancies can be stabilized by the carbon layer and hold its intrinsic properties for spontaneous oxygen activation without light irradiation, while common surface oxygen vacancies on TiO_2-x are always consumed by the capture of H₂O to form the surface hydroxyls. Thus, O₂ absorbed at the interface of carbon and TiO_2-x can be directly activated into singlet oxygen (¹O₂) or superoxide radicals (·O₂^-), confirmed both experimentally and theoretically. These reactive oxygen species exhibit excellent performance in oxidation reactions and inhibition of MCF-7 cancer cells, providing new insight into the effective utilization of O₂ via oxygen vacancies on metal oxides.

Phase Segregated Pt-SnO2 /C Nanohybrids for Highly Efficient Oxygen Reduction Electrocatalysis

Strengthening the interfacial interaction in heterogeneous catalysts can lead to a dramatic improvement in their performance and allow the use of smaller amounts of active noble metal, thus decreasing the cost without compromising their activity. In this work, a facile phase-segregation method is demonstrated for synthesizing platinum-tin oxide hybrids supported on carbon black (PtSnO₂ /C) in situ by air annealing PtSn alloy nanoparticles on carbon black. Compared with a control sample formed by preloading SnO₂ on carbon support followed by deposition of Pt nanoparticles, the phase-segregation-derived PtSnO₂ /C exhibits a more strongly coupled PtSnO₂ interface with lattice overlap of Pt (111) and SnO₂ (200), along with enhanced electron transfer from SnO₂ to Pt. Furthermore, the PtSnO₂ active sites show a strong ability to degrade reactive oxygen species. As a result, the PtSnO₂ /C nanohybrids exhibit both excellent activity and stability as a catalyst for the oxygen reduction reaction, with an overall performance which is superior to both the control sample and commercial Pt/C catalyst. This phase-segregation method can be expected to be applicable in the preparation of other strongly coupled nanohybrids and offers a new route to high-performance heterogeneous catalysts for low-cost energy conversion devices.

Uniform Pt nanoparticles supported on urchin-like mesoporous TiO2 hollow spheres as stable electrocatalysts for the oxygen reduction reaction

In order to promote the commercial application of proton exchange membrane fuel cells, it is of great importance to develop Pt-based electrocatalysts with high activity and stability for the oxygen reduction reaction (ORR). Here, urchin-like mesoporous TiO₂ hollow spheres (UMTHS) with a high specific surface area (167.1 m² g^-1) and improved conductivity were designed and applied as supports to disperse Pt nanoparticles (NPs) for the first time. Uniform Pt NPs (∼3.2 nm) on the surface of nanothorns were obtained after heat treatment. The as-prepared product (Pt/UMTHS) exhibited a more positive half-wave potential (E_h) than that of the reference sample Pt@C without UMTHS (0.867 V vs. 0.829 V). The improved performance can be ascribed to the high specific surface area of UMTHS. The Pt/UMTHS also exhibited a much better ORR stability than the commercial Pt/C after long-term cycling at 0.6-1.0 V according to the comparison of E_h, mass activity and electrochemical surface area with Pt/C. The enhanced stability of Pt/UMTHS was mainly derived from the strong metal support interaction between Pt NPs and UMTHS, together with the spatial restriction and the anti-restriction provided by UMTHS.

Significant promotion effects of Ag oxide towards Pd catalysis for ethanol and methanol oxidation reactions

Ag oxides play a crucial role in promoting the catalysis of Pd both for ethanol and methanol oxidation reactions.

Low-loading Pt nanoparticles embedded on Ni, N-doped carbon as superior electrocatalysts for oxygen reduction

A synergetic catalytic system was built based on Pt NPs and atomic Ni–N–C joint active sites for better ORR electrocatalysis.

Pt Nanoparticle-Loaded Graphene Aerogel Microspheres with Excellent Methanol Electro-Oxidation Performance

Platinum-decorated graphene aerogel microspheres were fabricated through a combined electrospraying, freeze-casting, and solvothermal process. Platinum nanoparticles with a narrow size distribution are evenly anchored on the graphene aerogel microspheres without agglomeration benefitting from the distinct center-diverging microchannel structure of the graphene aerogel microspheres, which results in the as-prepared catalysts presenting excellent electrocatalytic performance including high electrocatalytic activity and high poison tolerance toward methanol electro-oxidation, showing great potential for direct methanol fuel cell anode catalysts. In particular, the platinum-decorated graphene aerogel microspheres exhibit an extremely high mass activity of 1098.9 mA mg^-1 toward methanol oxidation as well as excellent antipoisoning ability, which are dramatically enhanced compared with Pt particles dispersed on graphene oxide and commercial carbon black supports.

An Oxygen-Vacancy-Rich Semiconductor-Supported Bifunctional Catalyst for Efficient and Stable Zinc-Air Batteries

The highly oxidative operating conditions of rechargeable zinc-air batteries causes significant carbon-support corrosion of bifunctional oxygen electrocatalysts. Here, a new strategy for the catalyst support design focusing on oxygen vacancy (OV)-rich, low-bandgap semiconductor is proposed. The OVs promote the electrical conductivity of the oxide support, and at the same time offer a strong metal-support interaction (SMSI), which enables the catalysts to have small metal size, high catalytic activity, and high stability. The strategy is demonstrated by successfully synthesizing ultrafine Co-metal-decorated 3D ordered macroporous titanium oxynitride (3DOM-Co@TiO_x N_y ). The 3DOM-Co@TiO_x N_y catalyst exhibits comparable activities for oxygen reduction and evolution reactions, but much higher cycling stability than noble metals in alkaline conditions. The zinc-air battery using this catalyst delivers an excellent stability with less than 1% energy efficiency loss over 900 charge-discharge cycles at 20 mA cm^-2 . The high stability is attributed to the strong SMSI between Co and 3DOM-TiO_x N_y which is verified by density functional theory calculations. This work sheds light on using OV-rich semiconductors as a promising support to design efficient and durable nonprecious electrocatalysts.

Enhanced Electrocatalytic Oxygen Reduction on NiWOx Solid Solution with Induced Oxygen Defects

The continuous solid solution NiWO_x is successfully prepared by using precursor W₁₈O₄₉ with plenty of oxygen defects. The NiWO_x nanoparticles are characterized by X-ray diffraction, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, and X-ray absorption spectroscopy. The crystallographic phase of NiWO_x is stable and characterized by the same feature of the parent lattice W₁₈O₄₉ even with various concentrations of dopant Ni which indicates the existence of oxygen defects. The NiWO_x nanoparticles could be processed as the appropriate promoter after loading 10 wt % Pt. The Pt/NiWO_x displays remarkable response for oxygen reduction reaction in alkaline medium compared with the commercial Pt/C. The analysis of the electrochemistry data shows that the existence of abundant oxygen defects in the solid solution NiWO_x is the key factor for the improved ORR catalyst performance. Ni is effective in the catalysts because of its compatibility with W in the solid solution and its active participation in oxygen reduction reaction.