Rarest Elements Research Articles

Kinetic Insights of Proton Exchange Membrane Water Electrolyzer Obtained by Operando Characterization Methods.

Benefiting from the merits of short response time, high current density, and differential pressure, the proton exchange membrane water electrolyzer (PEMWE) is attracting increasing attention from both academic and industry researchers. A limiting factor that impedes the widespread application of the PEMWE is its reliance on the rarest elements, such as iridium and platinum. In order to optimize the device performance as well as to reduce the usage of rare elements, it is important but difficult to directly observe the reaction within the electrolyzer under working conditions. Thus, operando characterization methods are urgently needed to probe in real time the water electrolysis process during operation. In this perspective, we highlight the important role and summarize the recent advances of operando characterization methods in obtaining kinetic insights about PEMWEs. Based on the demands of kinetic optimization, an outlook of future characterization methods is given at the end.

Wafer‐Scale Graphene Anodes Replace Indium Tin Oxide in Organic Light‐Emitting Diodes (Advanced Optical Materials 3/2022)

A novel use of large-area catalyst-free graphene to replace indium tin oxide (ITO) as an electrode in wafer-scale organic light emitting diodes is reported by Zhichao Weng, Colin J. Humphreys, William P. Gillin, and co-workers in article number 2101675. Indium is one of the nine rarest elements in the earth's crust. This research opens the door to replacing non-sustainable indium with sustainable graphene in optoelectronic devices.

End-of-life recycling rates of platinum group metals in the automotive industry: Insight into regional disparities

Platinum group metals, as the rarest elements in the lithosphere, are technological enablers in many modern industrial processes, especially in the automotive industry. Due to the limited availability of natural resources, increasing the recycling rate is essential for securing the supply of platinum group metals. This paper estimates the end-of-life recycling rates of platinum group metals in the automotive industry at the regional level during the period 2000–2017. The results show that in North America, Europe and Japan, the end-of-life recycling rates increased from very low levels in 2000 to above 50% in 2017. In contrast, they stayed at a significantly lower level in China. In-use stocks of platinum group metals in the automotive industry of North America, Europe, Japan and China reached over 3.65 kt in 2017 and included 1.33 kt of platinum, 1.95 kt of palladium and 0.37 kt of rhodium. These in-use stocks represent a major opportunity for secondary platinum group metal recovery. The priority for recycling improvement should be increasing the collection rate.

(Invited) Assessing Corrosion Resistance of Antimony-, Niobium- and Tantalum-Doped Tin Oxide Aerogels As Oxygen Evolution Reaction Catalyst Supports in Acidic Media

Despite the fact that iridium (Ir) is among the rarest elements on Earth [1], it remains the state-of-the-art anode electrocatalyst in Proton Exchange Membrane Water Electrolyzers (PEMWE). Indeed, Ir dioxide (IrO2) presents the best compromise between activity toward the Oxygen Evolution Reaction (OER) and stability under the harsh operating conditions of the anode: E > 1.5 V vs. the reversible hydrogen electrode (RHE), 60 < T < 80 °C, presence of oxygen and highly acidic environment [2].In this context, research efforts have been dedicated to minimize Ir loading without compromising OER activity and stability. One possible approach is to stabilize the metal nanoparticles (NPs) on a high surface area support. The classical carbon black supports, widely used in fuel cells, are easily oxidized in OER conditions: carbon corrosion leads to particle aggregation and eventually detachment from the support surface [3]. As an alternative to carbon, metal oxides such as tin dioxide (SnO2) [4] or titanium dioxide (TiO2) [5] feature a good corrosion resistance in PEMWE operating conditions and may strongly interact with the catalyst (strong metal–support interaction (SMSI) effect [6]).In this presentation, we shine a spotlight on iridium oxide (IrOx) NPs supported on SnO2 aerogels doped with, niobium (Nb), tantalum (Ta) or antimony (Sb). The aerogels, synthesized via a sol-gel process, feature a rutile structure after calcination, a specific surface area about 80 m2 g-1 and an electronic conductivity spanning from 5 mS cm-1 to 1 S cm-1 depending on the dopant [7-8]. A highly reproducible colloidal polyol route was used to deposit the IrOx NPs onto the aerogels, ensuring a straightforward comparison of their catalytic performance towards the OER and their resistance to corrosion. We used a home-made flow cell coupled to an inductively-coupled plasma mass spectrometer (ICP-MS) to assess metal dissolution under various potential conditions. As expected, carbon support proved to be unstable in OER conditions (Figure 1.a). In contrast, SnO2 aerogels clearly improved catalyst stability at high potential (Figures 1.b and 1.c). Especially, Ta-doped SnO2 (TaTO) aerogels showed an outstanding corrosion resistance with a negligible loss of dopant when compared to Sb-doped SnO2 (ATO). Based on our experimental observations, we demonstrate that a judicious doping of SnO2 aerogels could help developing highly active and robust OER electrocatalysts in acidic media.Figure 1. Metal concentration under staircase potential profiles from 0.9 V vs. RHE to 1.6 V vs. RHE in 100 mV steps with 300 seconds hold time at each potential for IrOx NPs deposed onto (a) Vulcan© XC-72, (b) ATO (10 at.% of Sb) and (c) TaTO (5 at.% of Ta) . The experiments were performed at room temperature by coupling a home-made flow cell to a PerkinElmer Nexion2000 ICP-MS instrument. A 0.05 M H2SO4 solution deaerated with argon was used as electrolyte. The catalyst ink was deposited on the surface of the glassy carbon electrode (4 mm in diameter) resulting in a loading of 20 μgIr cmgeo -2.

Sediment quality of Ergene River Basin: bio-ecological risk assessment of toxic metals.

Ergene River Basin is located in the north-west part of Marmara Region of Turkey. There are many industrial enterprises on its basin and as well as the majority of these facilities are located on the upstream of the basin. Therefore, Ergene River is one of the rare river ecosystems that are contaminated almost from the source area.The aim of this investigation was to assess the sediment contamination of Ergene River Basin including Meriç and Ergene Rivers and 10 significant tributaries of the system by investigating total of 25 macro- and micro-element concentrations. Sediments were sampled in spring season (rainy) of 2018 from 21 stations and element accumulations were investigated by using an ICP-MS.The investigated macro- and micro-elements in terms of concentration levels in abiotic components of the basin and the investigated basin components in terms of sediment quality characteristics were classified by using cluster analysis (CA). Biological Risk Index (mERM-Q) and Potential Ecological Risk Index (RI) were also applied to detected data to make an assessment of biological and ecological risks of toxic elements on the system.As a result of elemental CA, four statistically significant clusters were formed, which were named as "most intense elements", "moderate intense elements", "moderate rare elements", and "rarest elements". As a result of locational CA, three statistically significant clusters were formed, which were named as "low contaminated zone", "moderate contaminated zone", and "high contaminated zone". As a result of mERM-Q, chromium was determined as the most risky element, and as a result of RI, cadmium was determined as the most risky element for the sediments of Ergene River Basin.

Essential and toxic element bioaccumulations in fishes of gala and siğirci lakes (Meriç River Delta, Turkey)

Meriç River Delta is located in the Thrace Region of Turkey, and it is one of the most important wetlands worldwide. Gala and Sığırcı Lakes, which are known as significant lakes in Turkey in terms of especial biodiversity, are located in the Meriç River Delta and they are the main lentic factors of the system. The aim of this study was to evaluate the essential and toxic element bioaccumulation levels in fishes of Gala and Sığırcı Lakes from a statistical perspective by investigating a total of 25 macro- and micro-element bioaccumulations. One-Way ANOVA Test (OWAT) was applied to detected data in order to determine the statistical differences of element bioaccumulations among the fish species. Cluster analysis (CA) was also applied to detected data in order to classify the investigated elements in terms of bioaccumulation levels in fish tissues. According to the results of OWAT, although statistical differences were not recorded among the fish species in terms of essential element levels, significant statistical differences were recorded in terms of toxic element levels (P&lt;0.05). According to the results of CA, 5 statistically significant clusters were formed, which were named as “Most intense elements”, “Second most intense elements”, “Moderate intense elements”, “Second rarest elements”, and “Rarest elements”. It was also found that toxic element bioaccumulation rates in fishes of Gala Lake were significantly higher than in fishes of Sığırcı Lake (P&lt;0.05).

Dissolved platinum in rainwater, river water and seawater around Tokyo Bay and Otsuchi Bay in Japan

Platinum, among the rarest elements in the earth's crust, is now widely used in various products such as catalytic converters in automobiles and anticancer drugs. Consequently, the concentration of Pt in urban aquatic environments might be increasing. However, little is known about the distributions and geochemical cycles of Pt in aquatic environments because its overall concentration remains low. In this study, we examined dissolved Pt in river water and seawater around Tokyo Bay and Otsuchi Bay (Iwate Prefecture, Japan) and rainwater in the Tokyo area. To determine sub-picomolar levels of dissolved Pt, we used isotope-dilution Inductively Coupled Plasma Mass Spectrometry (ICP-MS) after column preconcentration with an anion exchange resin. We observed seasonal variation in the dissolved Pt concentrations in Tokyo rainwater in 2002; higher concentrations were found from January to March, which might be related to the pH of rainwaters. At the source of the Arakawa River in the greater Tokyo area, the dissolved Pt concentration was found to be similar to that in rainwater. Further downstream, the dissolved Pt concentration increased sharply, which seemingly reflects the anthropogenic input of Pt into the river. In a rural area in Japan (Otsuchi Bay), the dissolved Pt concentrations were lower than in Tokyo Bay. In this area, a sharp increase in dissolved Pt concentrations was observed in a high salinity region. Contrasting Pt distribution patterns between urban and rural areas indicate that strong anthropogenic Pt sources exist in urban estuaries and that geochemical processes within estuaries affect the Pt distribution.

Rare materials for photovoltaics: Recent tellurium price fluctuations and availability from copper refining

Of the materials of current research interest in thin-film photovoltaics, Ru and Te are amongst the nine rarest elements in the earth's crust, with In and Se in positions 11 and 14, raising the issue as to what constraints, if any, are placed on future thin-film photovoltaic manufacturing volumes by such scarcity. Te provides an interesting case study since more than 600 t has been incorporated into CdTe modules fielded to-date, with CdTe technology recently consolidating its position as the most successful commercial thin-film technology. The origin and impacts of recent fluctuating Te market conditions are discussed as are new insights into long-term supply from Cu refining.

The first finds of rhenium minerals in Karelia

Rhenium is one of the rarest elements of the earth crust (abundance ratio 0.7 mg/t). In the Karelian region, Re and accompanying Os were discovered in a copper-molybdenum-porphyry ore formation, represented by the Lobash deposit, the Jalonvaara occurrences etc., and in a noble-metal-Cu-U-vanadium ore formation (Padma Group occurrences). Molybdenites from the above deposits are enriched in Re and Os (Lobash: 13–187 g/t Re, 0.4–6 g/t Os). So far, however, no rhenium minerals proper have been revealed in the Karelian deposits and occurrences of the above formations or elsewhere. As a result of the microprobe study of mineral assemblages of cupreous sandstones from the Voronov Bor deposit (bornite ore) and sulphide-copper-nickel ore from the Rybozero deposit, osmium-cupreous rheniite (Re, Cu, Os, Fe)1S2 that contains 56.53–60.25% Re, 4.61–10.99% Cu, 1.52–3.77% Os and up to 4.75% Fe was revealed and studied for the first time.

The Geochemistry of Natural Technetium and Plutonium

Technetium and plutonium in unprocessed nuclear reactor wastes are major concerns with regard to their containment in the geologic environment. Both nuclides have long half-lives; therefore, they will exist long after engineered barriers can be considered reliable. Consequently, strategies for the containment of these two elements depend on their retention in the geologic barrier until they have decayed to innocuous levels. Because these are the rarest elements in nature, there have been few direct observations of their geochemical behavior; predictions con- cerning their fate in the repository are based on properties that can be observed in the laboratory. We are attempting to complement the laboratory work by studying the geochemistry of natural plutonium and technetium.