Scarcity Of Precious Metals Research Articles

Self-sustaining alkaline seawater electrolysis via forward osmosis membranes

Seawater electrolysis for hydrogen production faces inherent challenges, including side reactions, corrosion, and scaling, stemming from the intricate composition of seawater. In response, researchers have turned to continuous water splitting using forward osmosis (FO)-driven seawater desalination. However, the necessity of a neutral electrolyte hampers this strategy due to the limited current density and scarcity of precious metals. Herein, this study applies alkali-durable FO membranes to enable self-sustaining seawater splitting, which can selective withdraw water molecules, from seawater, via concentration gradient. The membranes demonstrated outstanding perm-selectivity of water/ions (∼5830 mol mol−1) during month-long alkaline resistance tests, preventing electrolyte leaching (>97% OH− retention) while maintaining ∼95% water balance (VFO = Velectrolysis) via preserved concentration gradient for consistent forward-osmosis influx of water molecules. With the consistent electrolyte environment protected by the polyamide FO membranes, the NiFe-Ar-P catalyst exhibits promising performance: a sustain current density of 360 mA cm−2 maintained at the cell voltage of 2.10 V and 2.15 V for 360 h in the offshore seawater, preventing Cl/Br corrosion (98% rejection) and Mg/Ca passivation (99.6% rejection). This research marks a significant advancement towards efficient and durable seawater-based hydrogen production.

Characterization of LaFe0.6Co0.4O3 washcoat layer on a monolithic substrate

Development of automotive three-way catalysts (TWC) is a critical research topic owing to the increasingly stringent emission regulations together with the price and scarcity of precious metals. Among different materials classes, perovskite-type oxides are known to be valuable alternatives because of their high catalytic activities and thermal stability. The interest in doped lanthanum ferrite perovskite as a catalyst is the concept of regeneration of catalyst nanoparticles, which makes it be used efficiently in automobile exhaust for longer duration in comparison to the conventional TWCs. B-site cation regeneration prevents particle growth and sulfur poisoning; hence, the consumption of precious metals will be reduced without lowering the catalytic performance. The aim of this study is to optimize the characteristics of a LaFe0.6Co0.4O3 (LFC) washcoat layer on a cordierite (2MgO.2Al2O3.5SiO2) monolithic substrate through dip coating of the slurry of amorphous and calcined nano-sized LFC particles. Experiments have been conducted to find the optimum amount of viscosity of the slurry, number of dipping repetitions, and suspension time in order to get the highest specific surface area and adherence to the substrate. Also, differences between a slurry with amorphous and calcined powder, precipitation agent and calcination temperature are investigated. It was found that a slurry with 8% w/w of LFC powder, 2% w/w of PVA, 1% w/w of HNO3, and 7.8% w/w of glycerol in water yields suitable slurry characteristics for the dip-coating purpose. SEM pictures were acquired to find out the morphology of the washcoat layer. By repeating the dip-coating process for two times with the calcined powder, a uniform and porous layer is formed on the monolithic substrate with particle size of around 200 nm after sintering at 900 °C.

Composite of Nickel Oxide Hexagonal Sheet Supported on Carbon Nitride for Photo-Electrochemical Water Splitting

Developing highly efficient and cost-effective electro-catalysts for the photo-electrochemical (PEC) water splitting is of great significance, since its two reactions, oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) is coupled with the key clean energy systems. However, the prohibitive costs and scarcity of precious metals used as OER and HER catalysts (e.g. IrO2, RuO2, Pt) limits the large scale commercialization. Herein, we report a facile and cheap novel organic-inorganic hetero-structured electro-catalyst: 2D nickel oxide (NiO) hexagonal sheet supported on graphitic-carbon nitride (g-C3N4) which has been successfully synthesized using in-situ solid-state heat treatment. The Transmission electron microscopy (TEM) characterization confirms that NiO are homogeneously dispersed on the surface of g-C3N4. The presented catalyst display outstanding activity in catalyzing PEC water splitting with a potential of 130 mV for OER and 5 mV for HER for the reaction to start. Moreover, the maximum current density obtained at an overpotential of 200 mV are 20 mAcm-2 and 1000 mAcm-2 for OER and HER, respectively. Our findings reveal that the rational interaction between two-dimensional materials can remarkably promote the hydrogen and oxygen production reactions, thus boosting the entire clean energy system. Furthermore, our work also reveals the importance of local transition metal coordination in catalysts for the OER and HER which would lead to new class of low-cost, durable and efficient water splitting catalysts. Figure 1

Structured Perovskite-Based Catalysts and Their Application as Three-Way Catalytic Converters—A Review

Automotive Three-Way Catalysts (TWC) were introduced more than 40 years ago. Despite that, the development of a sustainable TWC still remains a critical research topic owing to the increasingly stringent emission regulations together with the price and scarcity of precious metals. Among other material classes, perovskite-type oxides are known to be valuable alternatives to conventionally used TWC compositions and have demonstrated to be suitable for a wide range of automotive applications, ranging from TWC to Diesel Oxidation Catalysts (DOC), from NOx Storage Reduction catalysts (NSR) to soot combustion catalysts. The interest in these catalysts has been revitalized in the past ten years by the introduction of the concept of catalyst regenerability of perovskite-based TWC, which is in principle well applicable to other catalytic processes as well, and by the possibility to reduce the amounts of critical elements, such as precious metals without seriously lowering the catalytic performance. The aim of this review is to show that perovskite-type oxides have the potential to fulfil the requirements (high activity, stability, and possibility to be included into structured catalysts) for implementation in TWC.