Enhancing durability of automotive fuel cells via selective electrical conductivity induced by tungsten oxide layer coated directly on membrane electrode assembly

The poor durability, attributed to catalyst corrosion during start-up/shutdown (SU/SD), is a major obstacle to the commercialization of fuel cell electric vehicles (FCEVs). We recently achieved durability enhancement under SU/SD conditions by implementing a metal-insulator transition (MIT) using proton intercalation/deintercalation in WO3. However, such oxide-supported catalysts were unsuitable for direct application to the mass production stage of membrane electrode assembly (MEA) process due to their physical and chemical properties. Here, we report a unique approach that achieves the same durability enhancement in SU/SD situations while being directly applicable to the conventional MEA fabrication process. We coated WO3 on the bipolar plate, gas diffusion layer, and MEA to investigate whether the MIT phenomenon was realized. The WO3-coated MEA demonstrated 94% performance retention during SU/SD, the highest level to our knowledge. It can directly contribute to enhancing the durability of commercial FCEVs and be immediately applied to the MEA mass production process.

Self-Optimized Ligand Effect of Single-Atom Modifier in Ternary Pt-Based Alloy for Efficient Hydrogen Oxidation

Modifying the atomic and electronic structure of platinum-based alloy to enhance its activity and anti-CO poisoning ability is a vital issue in hydrogen oxidation reaction (HOR). However, the role of foreign modifier metal and the underlying ligand effect is not fully understood. Here, we propose that the ligand effect of single-atom Cu can dynamically modulate the d-band center of Pt-based alloy for boosting HOR performance. By in situ X-ray absorption spectroscopy, our research has identified that the potential-driven structural rearrangement into high-coordination Cu-Pt/Pd intensifies the ligand effect in Pt-Cu-Pd, leading to enhanced HOR performance. Thereby, modulating the d-band structure leads to near-optimal hydrogen/hydroxyl binding energies and reduced CO adsorption energies for promoting the HOR kinetics and the CO-tolerant capability. Accordingly, PtPdCu₁/C exhibits excellent CO tolerance even at 1,000 ppm impurity.

Z-Scheme Photocarrier Transfer Realized in Tungsten Oxide-Based Photocatalysts by Combining with Bismuth Vanadate Quantum Dots

Multicomponent photocatalysts with a Z-scheme charge transfer are promising in converting solar to hydrogen fuel because of their significantly improved light absorption and restrained photocarrier recombination while keeping their redox capacity. In this work, a composite photocatalyst of BiVO₄ quantum dot-decorated WO₃ nanosheet arrays was synthesized and investigated. The existence of the Z-scheme charge transfer behavior was confirmed by the redox probe technique. Such a Z-scheme charge transfer makes it possible to generate hydrogen without bias. An optimized photocatalyst produces a hydrogen generation rate of 0.75 μmol/h without bias and a photocurrent of 1.91 mA/cm² at 1.23 V versus RHE, which is about 70% higher than that of pure WO₃. We attributed these improvements to the enhanced light absorption, extended conduction band level of BiVO₄, as well as the unique charge transfer behavior in the Z-scheme structure. This work presents a generalizable method to improve the redox capacity of a variety of semiconductors through rationally selecting the building material blocks in view of energy levels.

Designing and Fabricating Ordered Mesoporous Metal Oxides for CO₂ Catalytic Conversion: A Review and Prospect

In the past two decades, great progress has been made in the aspects of fabrication and application of ordered mesoporous metal oxides. Ordered mesoporous metal oxides have attracted more and more attention due to their large surface areas and pore volumes, unblocked pore structure, and good thermal stabilities. Compared with non-porous metal oxides, the most prominent feature is their ability to interact with molecules not only on their outer surface but also on the large internal surfaces of the material, providing more accessible active sites for the reactants. This review carefully describes the characteristics, classification and synthesis of ordered mesoporous metal oxides in detail. Besides, it also summarizes the catalytic application of ordered mesoporous metal oxides in the field of carbon dioxide conversion and resource utilization, which provides prospective viewpoints to reduce the emission of greenhouse gas and the inhibition of global warming. Although the scope of current review is mainly limited to the ordered mesoporous metal oxides and their application in the field of CO₂ catalytic conversion via heterogeneous catalysis processes, we believe that it will provide new insights and viewpoints to the further development of heterogeneous catalytic materials.

WO3/Conducting Polymer Heterojunction Photoanodes for Efficient and Stable Photoelectrochemical Water Splitting

An efficient and stable heterojunction photoanode for solar water oxidation was fabricated by hybridization of WO₃ and conducting polymers (CPs). Organic/inorganic hybrid photoanodes were readily prepared by the electropolymerization of various CPs and the codeposition of tetraruthenium polyoxometalate (Ru₄POM) water-oxidation catalysts (WOCs) on the surface of WO₃. The deposition of CPs, especially polypyrrole (PPy) doped with Ru₄POM (PPy:Ru₄POM), resulted in a remarkably improved photoelectrochemical performance by the formation of a WO₃/PPy p-n heterojunction and the incorporation of efficient Ru₄POM WOCs. In addition, there was also a significant improvement in the photostability of the WO₃-based photoanode after the deposition of the PPy:Ru₄POM layer due to the suppression of the formation of hydrogen peroxide, which was responsible for corrosion. This study provides insight into the design and fabrication of novel photosynthetic and photocatalytic systems with excellent performance and stability through the hybridization of organic and inorganic materials.

Growth of carbon nanoshells on tungsten carbide for loading Pt with enhanced electrocatalytic activity and stable anti-poisoning performance

Nearly transparent carbon nanoshells precipitated on WC were prepared by deoxidization approach. After Pt were loaded on the composite, an electrocatalyst with excellent electrochemical activity and stable anti-poisoning properties was obtained.

The preparation of Cr2O3@WO3 hierarchical nanostructures and their application in the detection of volatile organic compounds (VOCs)

Unique hierarchical nanostructures of a Cr₂O₃@WO₃ sensor were prepared via a water bath method, showing extraordinary sensing properties for xylene.

Porous WO3–carbon nanofibers: high-performance and recyclable visible light photocatalysis

Template-free porous carbon nanofibers embedded with WO₃ (WO₃–CNF) were prepared by combining electrospinning and carbonization.

Mesostructured platinum-free anode and carbon-free cathode catalysts for durable proton exchange membrane fuel cells

As one of the most important clean energy sources, proton exchange membrane fuel cells (PEMFCs) have been a topic of extensive research focus for decades. Unfortunately, several critical technique obstacles, such as the high cost of platinum electrode catalysts, performance degradation due to the CO poisoning of the platinum anode, and carbon corrosion by oxygen in the cathode, have greatly impeded its commercial development. A prototype of a single PEMFC catalyzed by a mesostructured platinum-free WO3/C anode and a mesostructured carbon-free Pt/WC cathode catalysts is reported herein. The prototype cell exhibited 93% power output of a standard PEMFC using commercial Pt/C catalysts at 50 and 70 °C, and more importantly, CO poisoning-free and carbon corrosion-resistant characters of the anode and cathode, respectively. Consequently, the prototype cell demonstrated considerably enhanced cell operation durability. The mesostructured electrode catalysts are therefore highly promising in the future development and application of PEMFCs.

High surface area mesoporous LaFe(x)Co(1-x)O3 oxides: synthesis and electrocatalytic property for oxygen reduction

The mesoporous LaFe(x)Co(1-x)O3 oxides synthesized via a co-nanocasting method exhibit perovskite structure with ordered mesoporous structure and high specific surface area. These materials are electrocatalytically active and highly stable for oxygen reduction reaction (ORR) attributing to the Fe(3+)/Fe(2+) redox couple and electrical conductivity.

Template-free pseudomorphic synthesis of tungsten carbide nanorods

A unique nanorod-structured tungsten carbide material with high specific surface area of 198 m(2) g(-1) is successfully synthesized for the first time by pseudomorphic transformation of chemically synthesized WO(3) nanorods through a high-temperature method. An electrocatalyst composed of Pt nanoparticles supported on WC nanorods demonstrates higher electrocatalytic activity for methanol electro-oxidation, better tolerance to CO poisoning, and superior performance for cathodic electrocatalytic hydrogen evolution than a Pt/C catalyst. This work provides a novel method to synthesize high-surface-area nanorod-structured WC materials by preparing oxide precursors with the desired external morphology, thus offering great potential for a broad range of applications of these materials in related reaction systems.

Ultrafast coloring-bleaching performance of nanoporous WO3-SiO2 gasochromic films doped with Pd catalyst

The gasochromic performance and durability of WO(3)-based films can be improved by doping SiO(2) particles within WO(3) matrix forming nanoporous supporting network and dispersing Pd catalyst inside films with enhanced catalytic activity. Nanoporous WO(3)-SiO(2) composite films loaded with Pd catalyst were prepared by sol-gel dip-coating process and served as an active chromogenic layer to fabricate a double-glazed gasochromic device. The structure, morphology, optical properties and gasochromic performance of WO(3)-SiO(2) films were fully investigated. The WO(3)-SiO(2) films exhibit excellent gasochromic performance with ultrafast coloring rate of 14.8% per second (%/s) (WO(3): 2.84%/s) and bleaching rate of 44.1%/s (WO(3): 7.18%/s). The transmittance changed between 17.8 and 74.6% during coloring-bleaching cycles, and totally reversibility and stability were achieved.