Strong Interaction between Platinum Nanoparticles and Tantalum-Doped Tin Oxide Nanofibers and Its Activation and Stabilization Effects for Oxygen Reduction Reaction

Unlocking single-atom induced electronic metal-support interactions in electrocatalytic one-electron water oxidation for wastewater purification

Electro-oxidation is a promising green technology for decentralized wastewater purification. However, its efficacy is primarily constrained by the selectivity and efficiency of hydroxyl radical (•OH) generation through one-electron water oxidation. In this study, we elucidate the mechanism of electronic metal-support interactions (EMSI) of Ni single-atoms on antimony-doped tin oxide anode (Ni/ATO) to enhance •OH production and overall water treatment efficiency. We experimentally and theoretically investigate both the structural evolution process and micro-interface mechanisms associated with the EMSI effects induced by Ni single-atoms. The optimized electronic structures in the interfacial catalysts under EMSI conditions and the co-catalytic role of Ni single-atoms synergistically facilitate selective and efficient •OH generation, resulting in over a fivefold increase in its steady-state concentration and tenfold enhancement in pseudo-first-order rate constant of sulfamethoxazole degradation compared to those on bare ATO. With the EMSI, rapid electron transfer channels were established for a marked enhancement in the adsorption, conversion, and dissociation of interfacial H2O molecules. Notably, it is revealed that Ni single-atoms serve as co-catalytic sites, exhibiting a "H-pulling effect" that is crucial for •OH generation. The Ni/ATO anode demonstrates great efficiency in degrading various refractory organic pollutants, and effectively treats real pharmaceutical wastewater with low energy consumption. Furthermore, it presents remarkable stability and adaptability, while maintaining a minimal environmental footprint during wastewater treatment processes. This work addresses the theoretical gaps between EMSI effects and co-catalysis in electro-oxidation systems, while providing a robust technological solution for wastewater purification.

Research Progress on Preparation and Electrocatalytic Performance of Tin Dioxide Nanomaterials

In the contemporary era of rapid economic growth, addressing the energy issue constitutes a significant subject. In contrast to traditional fossil energy, fuel cells, through specific transformation routes, can generate more energy and reduce pollution under the same conversion relationship. Direct alcohol fuel cells, as a type of proton exchange membrane fuel cell, exhibit relatively superior performance. During the process of converting chemical energy into electrical energy, the conversion efficiency of the electrode is a crucial aspect of the fuel cell's performance, thereby giving rise to electrode electrocatalysis. Nevertheless, the noble metal catalysts employed in current direct alcohol fuel cells are confronted with issues such as high cost, susceptibility to poisoning, and poor durability. A new approach to these problems is urgently needed. Loading noble metals onto metal oxides has been verified as an effective means. Among them, tin dioxide has attracted the attention of researchers due to its outstanding stability, anti-toxicity, and its positive auxiliary role in electrocatalysis. This article will conduct a review of the research progress in loading noble metals on tin dioxide carriers for the electrocatalytic oxidation of small molecule alcohols from various microstructures and loading methods. Finally, the research on metal dioxide electrocatalysts is prospected.

A comprehensive activity-stability correlation study of tantalum-doped tin oxide as a support for iridium oxide in low loading water electrolysis cell anodes

A systematic study on the impact of the treatment temperature of IrO x supported onto doped-tin oxide (1 at% Ta-SnO2 and 10 at% Sb-SnO2) fibres led to electrocatalysts with high oxygen evolution reaction activity and resistance to degradation. The electrolytic performance was comparable to that of unsupported commercial IrO2 with seven times higher loading.

A Janus Platinum/Tin Oxide Heterostructure for Durable Oxygen Reduction Reaction

Designing efficient and durable electrocatalysts for oxygen reduction reaction (ORR) is essential for proton exchange membrane fuel cells (PEMFCs). Platinum-based catalysts are considered efficient ORR catalysts due to their high activity. However, the degradation of Pt species leads to poor durability of catalysts, limiting their applications in PEMFCs. Herein, a Janus heterostructure is designed for high durability ORR in acidic media. The Janus heterostructure composes of crystalline platinum and cassiterite tin oxide nanoparticles with carbon support (J-Pt@SnO2/C). Based on the synchrotron fine structure analysis and electrochemical investigation, the crystalline reconstruction and charge redistribution at the interface of Janus structure are revealed. The tightly coupled interface could optimize the valance states of Pt and the adsorption/desorption of oxygenated intermediates. As a result, the J-Pt@SnO2/C catalyst possesses distinguishing long-term stability during the accelerated durability test without obvious degradation after 40 000 cycles and keeps the majority of activity after 70 000 cycles. Meanwhile, the catalyst exhibits outstanding activity with half-wave potential at 0.905 V and a mass activity of 0.355 A mgPt -1 (2.7 times higher than Pt/C). The approach of the Janus catalyst paves an avenue for designing highly efficient and stable Pt-based ORR catalyst in the future implementation.

Tailoring Zirconia Supported Intermetallic Platinum Alloy via Reactive Metal-Support Interactions for High-Performing Fuel Cells

Developing efficient and anti-corrosive oxygen reduction reaction (ORR) catalysts is of great importance for the applications of proton exchange membrane fuel cells (PEMFCs). Herein, we report a novel approach to prepare metal oxides supported intermetallic Pt alloy nanoparticles (NPs) via the reactive metal-support interaction (RMSI) as ORR catalysts, using Ni-doped cubic ZrO2 (Ni/ZrO2) supported L10-PtNi NPs as a proof of concept. Benefiting from the Ni migration during RMSI, the oxygen vacancy concentrations in the support are increased, leading to an electron enrichment of Pt. The optimal L10-PtNi-Ni/ZrO2-RMSI catalyst achieves remarkably low mass activity (MA) loss (17.8 %) after 400,000 accelerated durability test cycles in a half-cell and exceptional PEMFC performance (MA=0.76 A mgPt -1 at 0.9 V, peak power density=1.52/0.92 W cm-2 in H2-O2/-air, and 18.4 % MA decay after 30,000 cycles), representing the best reported Pt-based ORR catalysts without carbon supports. Density functional theory (DFT) calculations reveal that L10-PtNi-Ni/ZrO2-RMSI requires a lower energetic barrier for ORR than L10-PtNi-Ni/ZrO2 (direct loading), which is ascribed to a decreased Bader charge transfer between Pt and *OH, and the improved stability of L10-PtNi-Ni/ZrO2-RMSI compared to L10-PtNi-C can be contributed to the increased adhesion energy and Ni vacancy formation energy within the PtNi alloy.

Synthesis of a Mesoporous SnO2 Catalyst Support and the Effect of Its Pore Size on the Performance of Polymer Electrolyte Fuel Cells

The aim of this study was to clarify the effectiveness and challenges of applying mesoporous tin oxide (SnO2)-based supports for Pt catalysts in the cathodes of polymer electrolyte fuel cells (PEFCs) to simultaneously achieve high performance and high durability. Recently, the focus of PEFC application in automobiles has shifted to heavy-duty vehicles (HDVs), which require high durability, high energy-conversion efficiency, and high power density. It has been reported that employing mesoporous carbon supports improves the initial performance by mitigating catalyst poisoning caused by sulfonic acid groups of the ionomer as well as by reducing the oxygen transport resistance through the Pt/ionomer interface. However, carbon materials in the cathode can degrade oxidatively during long-term operation, and more stable materials are desired. In this study, we synthesized connected mesoporous Sb-doped tin oxides (CMSbTOs) with controlled mesopore sizes in the range of 4-11 nm and tested their performance and durability as cathode catalyst supports. The CMSbTO supports exhibited higher fuel cell performance at a pore size of 7.3 nm than the solid-core SnO2-based, solid-core carbon, and mesoporous carbon supports under dry conditions, which can be attributed to the mitigation of the formation of the Pt/ionomer interface and the better proton conductivity within the mesopores even at the low-humidity conditions. In addition, the CMSbTO supports exhibited high durability under oxidative conditions. These results demonstrate the promising applicability of mesoporous tin oxide supports in PEFCs for HDVs. The remaining challenges, including the requirements for improving performance under wet conditions and stability under reductive conditions, are also discussed.

Batch synthesis of high activity and durability carbon supported platinum catalysts for oxygen reduction reaction using a new facile continuous microwave pipeline technology

Traditional synthesis methodologies for fuel cell catalyst production involve long reactions and uncontrollable reaction processes. Synthesis methods for the production of catalysts typically have difficulties to achieve catalysts materials with consistency, high activity, and durability. In this study, a fast, simple, and suitable continuous pipeline microwave method for catalyst mass production was developed, with the carbon carrier being treated at different temperatures simultaneously. The method herein developed resulted in carbon-supported platinum (Pt) catalysts with high activity and high durability. In addition, the half-wave potential of the catalyst exceeded 0.9 V, the electrochemical active surface area reached 85.7 m²-g_Pt^-1, and the mass specific activity reached 171.1 mA-mg^-1. Remarkably, after 30,000 cycles of Pt attenuation tests and 30,000 cycles of carbon carrier attenuation tests, the retention rate of the annealed carbon carrier catalyst reached 80 %. As a membrane electrode, the catalyst generated a single cell maximum power density of 1.4 W-cm^-2, and the Pt content reached 0.286 g_Pt-kW^-1. The work provides an effective and practical method for the mass production of high-performance and high-durability catalysts, which guiding significance for mass production of catalysts.

Platinum Nanocatalysts Supported on Defective Hollow Carbon Spheres: Oxygen Reduction Reaction Durability Studies

The durability and long-term applicability of catalysts are critical parameters for the commercialization and adoption of fuel cells. Even though a few studies have been conducted on hollow carbon spheres (HCSs) as supports for Pt in oxygen reduction reactions (ORR) catalysis, in-depth durability studies have not been conducted thus far. In this study, Pt/HCSs and Pt/nitrogen-doped HCSs (Pt/NHCSs) were prepared using a reflux deposition technique. Small Pt particles were formed with deposition on the outside of the shell and inside the pores of the shell. The new catalysts demonstrated high activity (>380 μA cm⁻² and 240 mA g⁻¹) surpassing the commercial Pt/C by more than 10%. The catalysts demonstrated excellent durability compared to a commercial Pt/C in load cycling, experiencing less than 50% changes in the mass-specific activity (MA) and surface area-specific activity (SA). In stop-start durability cycling, the new materials demonstrated high stability with more than 50% retention of electrochemical active surface areas (ECSAs). The results can be rationalised by the high BET surface areas coupled with an array of meso and micropores that led to Pt confinement. Further, pair distribution function (PDF) analysis of the catalysts confirmed that the nitrogen and oxygen functional groups, as well as the shell curvature/roughness provided defects and nucleation sites for the deposition of the small Pt nanoparticles. The balance between graphitic and diamond-like carbon was critical for the electronic conductivity and to provide strong Pt-support anchoring.

Inexpensive gram scale synthesis of porous Ti4O7 for high performance polymer electrolyte fuel cell electrodes

As a fuel cell catalyst support, more than 2 g of Magnéli phase Ti₄O₇ fine-particles were synthesized in a single reaction via an inexpensive route. The single-cell performance reached that of commercial carbon-supported platinum, with an excellent load cycle durability, one of the highest ever reported for oxide-supported platinum catalysts.

Eriobotrya japonica assisted green synthesis of g‐C3N4 nanocomposites and its exceptional photoactivities for doxycycline and rhodamine B degradation with mechanism insight

In this novel research work, for the first time, green g‐C3N4 nanocomposites have been synthesized by utilizing Eriobotrya japonica as a stabilizer and mediator. Based on DRS absorbance spectra, TGA, fluorescence spectra related to •OH amount, photoelectrochemical curves, TPD, and BET results, it has been confirmed the Eriobotrya japonica mediated green g‐C3N4 (G‐CNS) nanosheets are efficient, stable, and more than 2.4 times enhancement in activities as compared with conventional chemically synthesized g‐C3N4 nanosheets. In order to further improve the performance, the as‐synthesized green g‐C3N4 was modified with SnO2 nanosheets. Our results confirmed that coupling of SnO2 nanosheets prolonged the lifetime of charge carriers and provided catalytic function. Compared with pristine G‐CNS, the photocatalytic activity of the resulting 5SO/G‐CNS improved by 2.3 and 2.6 times, for doxycycline and rhodamine B degradation, respectively. In addition, the possible photodegradation pathway for doxycycline and RhB mineralization is proposed. Finally, this novel work will provide a new platform for the efficient green synthesis of g‐C3N4 based nanocomposite and its utilization for environmental remediation.

Development of a highly stable Pt-based ORR catalyst over Mn-modified polyaniline-based carbon nanofibers

A highly stable Pt-based ORR catalyst was developed over Mn-modified polyaniline-based carbon nanofibers with a high degree of graphitization.