Reactive Surface Area Research Articles

Photocatalytic hydrogen generation of monolithic porous titanium oxide-based glass\u2013ceramics

A large relative surface area is crucial for high catalytic activity. Monolithic catalysts are important catalytic materials because of minimal self-degradation. Regarding large surface area catalysts, the glass–ceramics (GCs) with high formability, obtained by heat-treatment of the precursor glass, are plausible candidates. This study examines the photocatalytic behaviour of porous GCs obtained after acid leaching of MgO–TiO2–P2O5 GCs. After heat-treatment, anatase TiO2 was precipitated along with other phases. The diffraction intensity ratio between anatase and other phases was the maximum for a heat-treatment temperature of 900 °C. After acid leaching of the GCs, the relative surface area decreased with increasing TiO2 fraction; the surface area was also affected by the sample morphology. H2 generation was observed from porous GCs, while GCs without etching exhibited approximately zero activity. Thus, it was demonstrated that high surface area and prevention of the reduction reaction to Ti(III) are important for tailoring monolithic photocatalytic materials.

Role of Carbonate in Thermodynamic Relationships Describing Pollutant Reduction Kinetics by Iron Oxide-Bound Fe2.

The reduction of environmental pollutants by Fe2+ bound to iron oxides is an important process that determines pollutant toxicities and mobilities. Recently, we showed that pollutant reduction rates depend on the thermodynamic driving force of the reaction in a linear free energy relationship that was a function of the solution pH value and the reduction potential, EH, of the interfacial Fe3+/Fe2+ redox couple. In this work, we studied how carbonate affected the free energy relationship by examining the effect that carbonate has on nitrobenzene reduction rates by Fe2+ bound to goethite (α-FeOOH). Carbonate slowed nitrobenzene reduction rates by inducing goethite particle aggregation, as evidenced by surface charge and particle size measurements. We observed no evidence for carbonate affecting Fe3+/Fe2+ reduction potentials or the mechanism of nitrobenzene reduction. The linear free energy relationship accurately described the data collected in the presence of carbonate when we accounted for the effect it had on the reactive surface area of goethite. The findings from this work provide a framework for determining why common groundwater constituents affect the EH-dependence of reaction rates involving oxide-bound Fe2+ as a reductant.

Estimation the reactive surface area of minerals during fluid-rock interaction in hydrothermal Jiangxi Province (SE China)

The reactive surface areas of the most abundant reacting minerals have been estimated in the granite hydrothermal field of Jiangxi Province in South-East China. The chemical composition of the sampled fluids was used as input data and the continuous equilibrium approach was assumed for the kinetic calculations. Dissolution rates and the reactive surface areas of different minerals were obtained by reconstructing the chemical evolution of the interacting fluids in a reaction process schema defined by a fractional degree of advance of the irreversible mass-transfer process. We found that the reactive surface area ratio of albite/K-feldspar varies by 2–3 orders of magnitude while that of biotite/K-feldspar ratio by 4 orders of magnitude. The obtained results indicate that mineral reactive surface areas are not constant during the fluid-granite interaction: higher reactive surface areas were obtained at higher pCO2 partial pressure (lower pH) compared to water with lower pCO2 partial pressure (higher pH). The eventual formation of secondary clay-minerals overlaying the primary ones may be responsible for decreasing the contact area of the rock-forming mineral in thermal waters having higher pH. The results of our investigation indicate that the reactive surface area of biotite play an important role in the CO2-neutralizing process of this area that in turn, controls the natural releasing of CO2 to the atmosphere in this area.

Insight into the Property Modification of Zr‐Incorporated Alumina Binary Mixed Oxides by XRD, TEM, XPS, TPD and IR

AbstractAl2O3 is known to be the most stable aluminum oxide and shows a large variety of applications. Incorporating a second metal to alumina is regarded as an effective strategy to modify its pristine material property. In this work, the binary ZrXAlOY (0 < X ≤ 1) mixed oxides synthesized by co‐precipitation method were studied by X‐ray diffraction (XRD), transmission electron microscopy (TEM), X‐ray photoelectron spectroscopy (XPS), NH3 temperature‐programmed desorption (NH3‐TPD) and pyridine adsorbed infrared (IR). It was disclosed that Zr incorporation (i. e., Zr content) and calcination temperature would bring about significant modifications on the material property of ZrXAlOY compounds, such as crystal structure, valence state, surface acidity etc. Among the series ZrXAlOY mixed oxides investigated, the Zr0.1AlOY solid calcined at 400 °C presented a highest reactive surface area and a strongest interaction between Zr4+ cations and Al3+ cations, located either in the homogeneously distributed Zr‐Al mixed oxide or at the ZrO2/Al2O3 interface. Thus an optimal proportion of Lewis acid sites with strong strength was obtained on this compound, which could be beneficial to acid‐catalyzed reactions either as catalyst or support material.

Self-Powered Gas Sensor Based on a Photovoltaic Cell and a Colorimetric Film with Hierarchical Micro/Nanostructures.

We report a new type of self-powered gas sensors based on the combination of a colorimetric film with hierarchical micro/nanostructures and organic photovoltaic cells. The transmittance of the colorimetric film with micro/nanostructures coated with N,N,N',N'-tetramethyl-p-phenylenediamine (TMPD) changes by reacting with NO2 gas, and it is measured as a current output of the photovoltaic cell. For this purpose, materials for the organic photovoltaic cells were carefully chosen to match the working wavelength of the TMPD. Micropost arrays and nanowires increase the surface area for the gas reaction and thus improve the transmittance changes by NO2 gas (6.7% change for the plain film vs 27.7% change for the film with hierarchical micro/nanostructures to 20 ppm of NO2). Accordingly, the colorimetric device with the hierarchical structures showed a response of ΔI/I0 = 0.27-20 ppm of NO2, which is a 71% improvement compared to that of the plain sensing film. Furthermore, it showed a high selectivity against other gases such as H2S and CO with almost negligible responses. Since the current output change of the photovoltaic cell is utilized as a sensor signal, no extra electrical power is required for the operation of gas sensors. We also integrated the sensor device with an electrical module and demonstrated a self-powered gas alarm system.

A novel electrode formed with electrospun nano- and micro-scale carbon fibers for aqueous redox flow batteries

This work reports on a novel electrode prepared with electrospun nano- and micro-scale carbon fibers for aqueous redox flow batteries. Larger fibers, ~10 μm in diameter, form larger pores to provide pathways for electrolyte flow, while smaller fibers, ~1 μm in diameter, increase active surface area for redox reactions. Brunauer-Emmett-Teller and pressure drop tests show that the specific surface area of the prepared dual-diameter electrode is doubled as compared with the large-fiber electrode, while the estimated permeability is enhanced by 1.4 times as opposed to the small-fiber electrode. The application of the dual-diameter electrodes to a vanadium redox flow battery allows the battery to achieve an energy efficiency of 84.78% at the current density of 100 mA cm−2, which is 13.57% higher than that with small-fiber electrodes, and 3.91% higher than that with large-fiber electrodes. Even at a high current density of 200 mA cm−2, the battery with the prepared electrode can still maintain the energy efficiency of 74.18%, which is 5.5% higher than that with large-fiber electrodes, and the battery with small-fiber electrodes cannot be operated at such high current density. This dual-diameter fibrous structure provides inspirations for the future electrode design in aqueous redox flow batteries.

Immobilizing magnetite onto quartz sand for chromium remediation

Magnetite nanoparticles are often promoted as remediation agents for heavy metals such as chromium due to their reactivity and high surface area. However, their small size also makes them highly mobile increasing the risk that reacted pollutants will be transported to different locations rather than being safely controlled. Released to aquatic environments, aggregation leads to a loss of their nano-specific properties and contaminant-removal capacity. We immobilized magnetite onto sand to overcome these issues whilst maintaining reactivity. We compare biogenic magnetite and abiogenic magnetite coated sand against magnetite nanoparticles. Magnetite coatings mostly exhibited a Fe(II)/Fe(III) ratio close to stoichiometry (0.5). We tested the efficacy of the magnetite-coated sand to adsorb chromium, with respect to biogenic/abiogenic nanoparticles. Langmuir-type sorption of Cr(VI) onto magnetite (4.32 mM total Fe) was observed over the tested concentration range (10–1000 μM). Biogenic nanoparticles showed the highest potential for Cr(VI) removal with maximum adsorption capacity (Qmax) of 1250 μmol Cr/g Fe followed by abiogenic nanoparticles with 693 μmol Cr/g Fe. All magnetite coated sands exhibited similar sorption behavior with average Qmax ranging between 257−471 μmol Cr/g Fe. These results indicate coating magnetite onto sand may be more suitable than free nanoparticles for treating environmental pollutants such as chromium.

Multi‐Structure Hollow Nanofibers: Controlled Synthesis and Photocatalytic Applications

AbstractSolar‐driven semiconductor photocatalysts for solving global energy shortage and environmental pollution have attracted massive attention. Multi‐structure hollow nanofibers (MSHFs) photocatalyst offers many advantages, including abundant surface area for multiple light harvesting and interface redox reaction, heterostructured thin shell for expediting charge separation and transportation and large length‐diameter ratio for easily recycling. Herein, we summarize the latest development of MSHFs materials in terms of controlled synthesis approaches and applications in photocatalysis. The synthetic strategies are mainly classified into two categories, containing templating method and electrospinning approach. These MSHFs have wide applications in H2 production, CO2 reduction, organic compound degradation and dye‐sensitized solar cells (DSSCs). To the end of the review, perspectives on the future research and development of MSHFs are also discussed.

Engineering 3D electron and ion transport channels by constructing sandwiched holey quaternary metal oxide nanosheets for high-performance flexible energy storage

Due to the enhanced electrochemical activities, mixed metal oxides offer new and fascinating opportunities for high-performance supercapacitor electrodes. However, sluggish ionic and electronic kinetics within the electrode fundamentally limit further improvement of their electrochemical performance. To compensate for the deficiency, a flexible electrode (CNTF/Ni-Co-Mn-Mo NS/CNTN) composed of vertically-aligned areolate quaternary metal oxide nanosheets sandwiched between carbon nanotubes (CNTs) is constructed in this study, which demonstrates a unique hierarchical porous structure that can provide three-dimensional transport channels for both ions and electrons. The vertically aligned areolate quaternary metal oxide nanosheets enable increased exposed surface area and paths for ion transport, diffusion and redox reactions, resulting in an evident enhancement in electrochemical activities. Besides, the CNT networks provide improved conductivity, which can accelerate the electron transport. As a result, the flexible supercapacitor based on the CNTF/Ni-Co-Mn-Mo NS/CNTN electrode demonstrates a specific areal capacitance of 3738 mF cm−2, corresponding to a high energy density of 1.17 mW h cm−2, which outperforms most of the flexible devices reported recently. Additionally, excellent flexibility of up to 180° bend and superior performance stability of 87.87% capacitance retention after 10,000 charge-discharge cycles can be obtained. This unique design opens up a new way in the development of flexible energy storage devices with high performance.

BiVO4 Photoanode Modification by In-Doping and Anoxic Annealing by Synergistic Regulation

In this work, we fabricate a semitransparent BiVO4 photoanode via the synergistic effect of indium (In) doping and anoxic annealing. An optimized photocurrent density of 3.6 mA cm–2 at 2 V versus reversible hydrogen electrode is obtained in a sacrificial free electrolyte system (AM 1.5G 100 mW cm–2). In-doping increases the difficulty to form bonds between Bi atoms and O atoms in the crystal bulk. Thus, quasi-oxygen vacancies in the bulk of the BiVO4 crystal can be induced under anoxic annealing to increase the mobility, lifetime, and concentration of the photogenerated carriers. On the other hand, anoxic annealing can inhibit the conversion rate of the BiOI nanosheet arrays to BiVO4 to form a nanonet structure with a large surface reaction area. Therefore, through a simple In-doping and controlled anoxic annealing process, the photogenerated carriers and the nanomorphology of BiVO4 photoanode are synergistically optimized.

Rapid Mineral Precipitation During Shear Fracturing of Carbonate‐Rich Shales

AbstractTarget subsurface reservoirs for emerging low‐carbon energy technologies and geologic carbon sequestration typically have low permeability and thus rely heavily on fluid transport through natural and induced fracture networks. Sustainable development of these systems requires deeper understanding of how geochemically mediated deformation impacts fracture microstructure and permeability evolution, particularly with respect to geochemical reactions between pore fluids and the host rock. In this work, a series of triaxial direct shear experiments was designed to evaluate how fractures generated at subsurface conditions respond to penetration of reactive fluids with a focus on the role of mineral precipitation. Calcite‐rich shale cores were directly sheared under 3.5 MPa confining pressure using BaCl2‐rich solutions as a working fluid. Experiments were conducted within an X‐ray computed tomography (xCT) scanner to capture 4‐D evolution of fracture geometry and precipitate growth. Three shear tests evidenced nonuniform precipitation of barium carbonates (BaCO3) along through‐going fractures, where the extent of precipitation increased with increasing calcite content. Precipitates were strongly localized within fracture networks due to mineral, geochemical, and structural heterogeneities and generally concentrated in smaller apertures where rock:water ratios were highest. The combination of elevated fluid saturation and reactive surface area created in freshly activated fractures drove near‐immediate mineral precipitation that led to an 80% permeability reduction and significant flow obstruction in the most reactive core. While most previous studies have focused on mixing‐induced precipitation, this work demonstrates that fluid–rock interactions can trigger precipitation‐induced permeability alterations that can initiate or mitigate risks associated with subsurface energy systems.

Shuangyin Wang.

"The secret of being a successful scientist is to do your own and labeled research … In my first experiment I unintentionally functionalized carbon nanotubes, on which Pt nanoparticles were deposited uniformly. Luck is part of research …" Find out more about Shuangyin Wang in his Author Profile.

EDMed Inconel 718 using powder metallurgy (P/M) sintered electrode made with nano and micron sized powders

This work presents experimental data carried out for surface modification of Inconel 718 using WC/Cu composite powder metallurgy (P/M) electrodes made of nano and micron sized particles. Both machine and tool parameters were selected for study and experiments were planned as per Taguchi’s L18 mixed orthogonal array in order to find the influence of parameters on surface roughness (SR) and micro-hardness (MH). Peak current, particle size and pulse on time were found to be most significant on both SR and MH. High reactive surface area of nano particles made surface alloying greater than the other tool electrodes and has shown its influence positively on both SR and MH. The EDX analysis reveals the migration of WC and Cu elements and deposition of carbon and oxygen particles on the surface. The XRD spectrum confirms presence of carbides (WC, W2C, Fe5C2, Cr7C3, Fe7C3 and Fe3C), oxides (Fe3O4, WO3 and Cr3O) and other intermetallics at different machining conditions indicating the influence of Pulse on time (TON) and Peak current (IP) on discharge energies and in turn on the properties of machined surface. The carbides generated on the machined surface increased the hardness to 845HV without much sacrifice of the roughness of the machined surface. The range of roughness values obtained in the present investigation is 2.443 to 4.098µm.

Mesoporous manganese silicate composite adsorbents synthesized from high-silicon iron ore tailing

Iron ore tailing (IOT) as a solid waste has attracted attention worldwide owing to the potential safety hazards and waste of resources. However, few studies focused on exploiting the structural characteristics of IOT. IOT is a special silicate mineral mixture composed of, for example, quartz, anorthite, microcline, and clinochlore which contain adjustable silica tetrahedron structures. In our research, Mn2+ was introduced to hydrothermally react with the adjustable silica tetrahedrons of IOT with the aid of sodium silicate, to provide IOT with reactive Mn-OH groups and high specific surface areas by constructing functional value-added mesoporous manganese silicate (MS) composites. It was found that the specific surface area (SBET) of IOT improved from 6.3 to 448.2 m2g−1 and achieved ideal pore size distributions after being transformed into MS composites. The composite obtained exhibited an excellent selective adsorption performance that could rapidly remove 100% methylene blue (MB) molecules from the mixed cationic dye solutions within 1min. The adsorption behavior was well described by pseudo second-order model and Freundlich isotherm model, indicating the chemical adsorption and multi-layer adsorption. The maximum adsorption capacity was up to 217mgg−1 (25°C, pH=7, adsorption time: 120min, MB initial concentration: 400mgL−1). Through investigation, it was found that the selective adsorptive ability is based on the hydrogen bonding and the suitable mesoporous structure for MB molecules.

Effects of air oxidation on the evolution of surface area within nuclear graphite and the contribution of macropores

Reactive surface area and its evolution play an important role in the oxidation behavior of porous carbon materials. Here, the evolution of reactive surface area within nuclear graphite grades NBG-18, IG-110, and PCEA were examined using chronic oxidation experiments interrupted with short thermal gravimetric analyses. To help interpret the observed changes in reactive surface area, the contribution of macropore total surface area was estimated using X-ray computed tomography with repeated morphological dilations of the digitally isolated pore structure. For these nuclear graphites, the reactive surface area changes by more than an order of magnitude between 0 and 70% conversion. Surface roughening, macropore opening and evolution, as well as late exposure of filler material likely contribute to the observed behavior of reactive surface area in these nuclear graphites.

Uniquely designed surface nanocracks for highly efficient and ultra-stable graphite felt electrode for vanadium redox flow battery

Large-scale activation of graphite felt electrode through a simple and cost-effective method is an imperative need for application of vanadium redox flow battery (VRFB). Here we report a rapid and low-cost method to develop highly functionalized activated graphite felt with uniformly distributed surface nanocracks (⁓30 nm × ⁓100 nm). Surface area, size, and distribution of surface nanocracks on electrode were controlled by tuning the process conditions and superior functionality was achieved through nitrogen doping. The activated graphite electrode with highly functionalized surface nanocracks offers improved pathways for electrolyte flow and improved hydrophilicity with high specific surface area (⁓19 m2g−1) for efficient vanadium redox reactions. The VRFB having activated graphite felt and nitrogen-doped alkaline graphite felt yield energy efficiencies as high as 89.6% and 87.4% at 50 mA cm−2, which is 18.3% and 15.4% higher than untreated graphite felt, respectively. Moreover, the VRFBs having activated graphite felt and nitrogen-doped activated graphite felt provide electrolyte utilization of 82.41% and 91.12% at 50 mA cm−2, 91.51% and 111.7% higher than that with untreated graphite felt. Additionally, the VRFBs were able to perform charge-discharge even at high current density of 200 mA cm−2 with electrolyte utilization of 41.78% and 61.09%, respectively.

Remediation by waste marble powder and lime of jarosite-rich sediments from Portman Bay (Spain)

We investigate the use of hydrated lime and calcite waste marble powder as remediation treatments of contaminated jarosite-rich sediments from Portman Bay (SE, Spain), one of the most contaminated points in the Mediterranean coast by mining-metallurgical activities. We tested two commercial hydrated limes with different Ca(OH)2 percentages (28 and 60% for Lime-1 and Lime-2 respectively) and two different waste marble powder, WMP, from the marble industry (60 and 96% of calcite for WMP-1 and WMP-2 respectively). Mixture and column experiments and modelling of geochemical reactions using PHREEQC were performed. Lime caused the precipitation of hematite, gypsum and calcite, whereas WMP treatments formed iron carbonates and hematite. The fraction of amorphous phases was mainly composed of iron oxides, hydroxides and oxyhydroxides that was notably higher in the lime treatment in comparison to the WMP treatment. The reactive surface area showed a positive trend with the amorphous phase concentration. Results highlighted the effectiveness of lime treatments, where Lime-2 showed a complete elimination of jarosite. Column experiments revealed a clear reduction of heavy metal concentration in the lixiviate for the treated sediments compared to the original sediments. Particularly, Lime-2 showed the highest reduction in the peak concentration of Fe, Mn, Zn and Cd. The studied treatments limited the stabilisation of Cr and Ni, whereas contrarily As increases in the treated sediment. PHREEQC calculations showed that the most concentrated heavy metals (Zn and Mn) are stabilized mainly by precipitation whereas Cu, Pb and Cd by a combination of precipitation and sorption processes. This chemical environment leads to the precipitation of stable iron phases, which sorb and co-precipitate considerable amounts of potentially toxic elements. Lime is significantly more effective than WMP, although it is recommended that the pH value of the mixture should remain below 9 due to the amphoteric behaviour of heavy metals.

Ti-in-quartz: Evaluating the role of kinetics in high temperature crystal growth experiments

We present results from 25 hydrothermal quartz growth experiments, all conducted at 800 °C and 1 kbar but with varying starting materials and run times, to address discrepancies between calibrations of the titanium-in-quartz (TitaniQ) thermobarometer. In our experiments, a gold capsule is loaded with silica glass, water, and either rutile or anatase as the TiO2 source. In most experiments, there is also a large quartz seed crystal contained in an open inner capsule. The use of rutile versus anatase has a significant influence on the (re)crystallization pathways of the SiO2 and TiO2 components. When rutile is used, quartz overgrowths have abundant open cavities and complex zonations. The rutile does not completely dissolve because rutile is the stable TiO2 polymorph, and yet, new rutile forms at the quartz seed-overgrowth interface and on the outer surface of quartz crystals. This suggests crystallization of quartz near Ωrut ∼ 1, but wide-ranging Ti concentrations and zonations in quartz are indicative of kinetic effects. When powdered anatase is used, the quartz overgrowths look markedly different, lacking the open cavities and instead exhibiting step edges and terraces. The Ti concentrations in quartz from these experiments are also wide-ranging but reach larger values.Our results span the range of previous calibrations and indicate that Ti concentrations in quartz are sensitive to the TiO2/SiO2 ratio of the fluid as opposed to the absolute concentration (or activity) of dissolved TiO2. We present a kinetic model for quartz and rutile growth from a fluid where the input parameters are the initial degrees of supersaturation with respect to quartz and rutile, the total reactive surface area, and rate constants that link the degree of supersaturation to net precipitation rates. The model can explain many of the salient features of our experimental results, as well as those from previous studies, but requires that the rate constant multiplied by the reactive surface area for rutile is less than that of quartz, and that rutile solubility depends on the SiO2 concentration of the fluid, as documented in the recent literature. Complete quartz-rutile equilibrium may not have been established in any of the experimental studies, but low-pressure experiments with slowly grown quartz seem to be more reliable than extrapolations from high-pressure experiments for thermobarometry of shallow natural systems.

Engineered carbon mineralization in ultramafic rocks for CO2 removal from air: Review and new insights

Carbon Dioxide removal from air (CDR) combined with permanent solid storage can be accomplished via carbon mineralization in ultramafic rocks in at least four ways:1. Surficial CDR: CO2-bearing air and surface waters are reacted with crushed and or ground mine tailings, alkaline industrial wastes, or sedimentary formations rich in reactive rock fragments, all with a high proportion of reactive surface area. This can be implemented at a low cost, but most proposed methods have a very large area footprint at the gigatonne scale. The area requirement can be greatly reduced by calcining (heating to produce pure CO2 for permanent storage or use) followed by recycling of MgO, CaO, Na2O, … Such looping methods have predicted costs that are as low or lower than for direct air capture with synthetic sorbents or solvents (DACSS), and a similar area footprint.2. In situ CDR: CO2-bearing surface waters are circulated through rock formations at depth. These methods potentially have a cost similar to that of surficial carbon mineralization, and a giant storage capacity with reduced surface area requirements, but they involve uncertain feedbacks between permeability, reactive surface area, and reaction rate, providing a fascinating topic for fundamental research. Furthermore, the size, injectivity, permeability, geomechanics, and microstructure of key subsurface reservoirs for in situ CDR remain almost entirely unexplored.3&4. Combined partial enrichment of CO2 using direct air capture with synthetic sorbents (DACSS) plus surficial carbon mineralization (3) or in situ carbon mineralization (4). Energy requirements and total costs for partial enrichment of CO2 are substantially lower than for enrichment to high purity. CO2 enriched air can be sparged through mine tailings at the surface, and/or through water to increase dissolved carbon concentrations prior to circulation through rock reactants. Such combined or hybrid approaches have not been investigated thoroughly, and offer many avenues for optimization.

Solvent-free synthesis of N-doped nanoporous carbon materials as durable high-performance pH-universal ORR catalysts

Metal-free carbons as durable high-performance oxygen reduction electrocatalysts, deemed to be promising alternatives to the platinum-group metals (PGMs), are vital to large-scale commercialization of fuel cells. Herein, a solvent-free synthetic strategy has been proposed to prepare N-doped nanoporous metal-free carbonaceous materials originating from various types of plant residues (papaya skin – fruit, bamboo shoot – forestry, wheat straw – farming and cabbage stem – vegetable). The optimal metal-free carbon, possessing maximized reaction surface area and optimized distributions of nanopore structures and nitrogen species, can function as the durable high-performance pH-universal ORR electrocatalyst, reaching or surpassing the benchmark 20% Pt/C catalyst within the wide scope of pH. This paper substantiates the solvent-free, scalable and bio-universal preparation approach to converting various biomass wastes into durable high-performance pH-universal ORR carbonaceous catalysts, capable of expanding the repertoire of cathode catalysts employed by fuel cells that demand diverse pH environments.