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

Abstract

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.

Structural, optical, and dielectric properties of hydrothermally synthesized SnO2 nanoparticles, Cu/SnO2, and Fe/SnO2 nanocomposites

“…Tin oxide (SnO 2 ) is an n-type semiconductor characterized by a wide band gap (∼3.6 eV) and electron mobility of 160 cm 2 V −1 s −1 at room temperature (RT) as a result of Sn interstitial defects and oxygen vacancies [9][10][11]. The incorporation of 3d transition metal (M) into SnO 2 to form M/SnO 2 composites is commonly utilized to reduce their particle size and hence enhance their physical and chemical properties [12][13][14].…”

Negatively charged platinum nanoparticles on dititanium oxide electride for ultra-durable electrocatalytic oxygen reduction

“…In this context, the electronic MSI is a crucial factor to determine the ORR catalytic activity and stability in the supported Pt nanocatalysts. 11–16 Indeed, electronic MSI-induced charge transfer has a profound impact on the catalytic behaviour of Pt NPs on various supporting materials, 12,13 where a change in the oxidation states of Pt atoms occurs. 14 However, this phenomenon generally arises at the interfacial region within a few atomic layers.…”

Probing the Formation and Evolution of Pd Nanoparticles on the Surface of γ-Al2O3 Using a Pd(II) Coordination Polymer as a Precursor: An In Situ X-ray Scattering and Spectroscopy Study

“…The presence of γ-Al 2 O 3 during the pyrolysis of supramolecules can lead to the design of heterogeneous catalysts with well-controlled NP size distribution, structure, morphology, and speciation. One of the contemporary challenges during the synthesis of NPs is to trace and control the structure, morphology, and defects in NPs. ,, In heterogeneous supported NP catalysts, the small size and low mass fraction of the NPs in comparison to the support are a tremendous characterization challenge. In this work, we employed X-ray total scattering with pair distribution function (PDF) analysis, which was complemented by high-resolution transmission electron microscopy (HR-TEM) and X-ray absorption spectroscopy (XAS) to probe the formation and evolution of Pd NPs on the surface of γ-Al 2 O 3 by the thermal decomposition of the Pd­(II)-CP.…”