IrO2–SiO2 binary oxide films: Preparation, physiochemical characterization and their electrochemical properties

Silica-Derived Nanostructured Electrode Materials for ORR, OER, HER, CO2RR Electrocatalysis, and Energy Storage Applications: A Review

Silica-derived nanostructured catalysts (SDNCs) are a class of materials synthesized using nanocasting and templating techniques, which involve the sacrificial removal of a silica template to generate highly porous nanostructured materials. The surface of these nanostructures is functionalized with a variety of electrocatalytically active metal and non-metal atoms. SDNCs have attracted considerable attention due to their unique physicochemical properties, tunable electronic configuration, and microstructure. These properties make them highly efficient catalysts and promising electrode materials for next generation electrocatalysis, energy conversion, and energy storage technologies. The continued development of SDNCs is likely to lead to new and improved electrocatalysts and electrode materials. This review article provides a comprehensive overview of the recent advances in the development of SDNCs for electrocatalysis and energy storage applications. It analyzes 337,061 research articles published in the Web of Science (WoS) database up to December 2022 using the keywords "silica", "electrocatalysts", "ORR", "OER", "HER", "HOR", "CO2RR", "batteries", and "supercapacitors". The review discusses the application of SDNCs for oxygen reduction reaction (ORR), oxygen evolution reaction (OER), hydrogen evolution reaction (HER), carbon dioxide reduction reaction (CO2RR), supercapacitors, lithium-ion batteries, and thermal energy storage applications. It concludes by discussing the advantages and limitations of SDNCs for energy applications.

First Iridium(IV) Chloride-Dimethyl Sulfoxide Complex [H(dmso)2][IrCl5(dmso-κO)]: Synthesis and Structure along with Novel Polymorph Modifications of [H(dmso)2][trans-IrCl4(dmso-κS)2] and [H(dmso)][trans-IrCl4(dmso-κS)2]

As evidenced by UV-Vis and EPR spectroscopies, the reaction of H₂IrCl₆·6H₂O or Na₂[IrCl₆]·nH₂O with DMSO results in a slow reduction of Ir(IV) avoiding the formation of Ir(IV) dimethyl sulfoxide complexes in measurable quantities. More specifically, we successfully isolated and solved the crystal structure of a sodium hexachloridoiridate(III), Na₃[IrCl₆]·2H₂O, as a product of Na₂[IrCl₆]·nH₂O reduction in an acetone solution. Furthermore, it was shown that [IrCl₅(Me₂CO)]^- species is gradually formed in an acetone solution of H₂IrCl₆·6H₂O upon storage. The reaction of DMSO with aged acetone solution of H₂IrCl₆·6H₂O dominated by [IrCl₅(Me₂CO)]^- affords a novel iridium(IV) chloride-dimethyl sulfoxide salt [H(dmso)₂][IrCl₅(dmso-κO)] (1). The compound was characterized by various spectroscopies (IR, EPR, UV-Vis) and X-ray diffraction techniques applied both to single-crystal and polycrystalline powder. The DMSO ligand is coordinated to the iridium site via the oxygen atom. New polymorph modifications of known iridium(III) complexes [H(dmso)₂][trans-IrCl₄(dmso-κS)₂] and [H(dmso)][trans-IrCl₄(dmso-κS)₂] were isolated and structurally elucidated as byproducts of the above reaction.

Optimized Mo-doped IrOx anode for efficient degradation of refractory sulfadiazine

Electrochemical advanced oxidation processes (EAOPs) is considered to be an efficacious method to degrade antibiotics. However, the performance of the anode has become the main limiting factor of this technology. In this study, due to the electron-deficient characteristics and the improvement of OER performance of Mo, we chose to use thermal decomposition to incorporate Mo into IrO2 to prepare anodes with industrial applicability. Under the optimal ratio of Ir to Mo is 7:3, (Ir0.7Mo0.3)Ox electrode's particular pore structure can expose more active sites and create a channel for the transportation of electrons, thereby promoting the formation of free radicals and degrading pollutants more efficiently. (Ir0.7Mo0.3)Ox electrode also has a higher mass activity (6.332 A g-1, three times that of the IrO2 electrode) and a larger electrochemical active area (ECSA, 375.43 cm2, seven times that of the IrO2 electrode). In addition, the optimal conditions of (Ir0.7Mo0.3)Ox electrode for degrading sulfadiazine(SDZ) were explored, which achieved a higher removal than traditional electrodes (90% removal within 4 h) when the Ti plate was the substrate. Through the intermediate products of SDZ degradation and related literatures, two possible degradation pathways of SDZ were speculated. This research provides a new type of anode catalyst for the degradation of sulfonamide antibiotics, which is possible for industrial application.

Anticatalytic Strategies to Suppress Water Electrolysis in Aqueous Batteries

Aqueous electrolytes are the leading candidate to meet the surging demand for safe and low-cost storage batteries. Aqueous electrolytes facilitate more sustainable battery technologies due to the attributes of being nonflammable, environmentally benign, and cost effective. Yet, water's narrow electrochemical stability window remains the primary bottleneck for the development of high-energy aqueous batteries with long cycle life and infallible safety. Water's electrolysis leads to either hydrogen evolution reaction (HER) or oxygen evolution reaction (OER), which causes a series of dire consequences, including poor Coulombic efficiency, short device longevity, and safety issues. These are often showstoppers of a new aqueous battery technology besides the low energy density. Prolific progress has been made in the understanding of HER and OER from both catalysis and battery fields. Unfortunately, a systematic review on these advances from a battery chemistry standpoint is lacking. This review provides in-depth discussions on the mechanisms of water electrolysis on electrodes, where we summarize the critical influencing factors applicable for a broad spectrum of aqueous battery systems. Recent progress and existing challenges on suppressing water electrolysis are discussed, and our perspectives on the future development of this field are provided.

Nanoporous IrO2 catalyst with enhanced activity and durability for water oxidation owing to its micro/mesoporous structure

Herein, we report a nanoporous IrO₂ catalyst with a surface area of 363.3 m² g^-1, the highest ever reported. The IrO₂ catalysts were prepared by a facile ammonia-induced pore-forming method, and efficiently scaled up to several kilograms. Bimodal micro/mesopores were created at once without using a template. For the IrO₂ (1 : 100)-450 °C (H₂IrCl₆ : NH₃·H₂O of 1 : 100) catalyst, the overpotential to attain a current density of 10 mA cm^-2 for water oxidation was only 282 mV, and furthermore, its excellent durability was confirmed by accelerated durability tests. Moreover, the overall voltage to achieve a current density of 1000 mA cm^-2 in a water electrolysis cell was only 1.649 V, making IrO₂ (1 : 100)-450 °C a highly attractive catalyst for water electrolysis applications.

An IrSi oxide film as a highly active water-oxidation catalyst in acidic media

We report an acid-stable IrSi oxide film made by MOCVD of an Ir^V complex for electrochemical water-oxidation.

Electrochemical degradation of the antibiotic metronidazole in aqueous solution by the Ti/SnO2-Sb-Ce anode

Metronidazole (MNZ) is an antibiotic pollutant with a high occurrence in the ambient medium. In this study, the anode material Ti/SnO2-Sb-Ce prepared in the lab was employed to investigate the feasibility of the electrochemical process to treat antibiotic in wastewater. The result showed that metronidazole could be effectively removed using Ti/SnO2-Sb-Ce. The degradation efficiency of 88% was obtained under the current density 1.6 mA cm(-2), pH = 5.6 (not adjusted), electrolyte (Na2SO4) concentration of 0.2 M for electrolysis 2 h. The removal percentage was higher by 17% compared with the control when the bare Ti was applied. Meanwhile, the energy consumption on Ti/SnO2-Sb-Ce was about one-seventh of that on Ti. The characterization of the material was conducted by the thermal field emission scanning electron microscope (FE-SEM), energy-dispersive X-ray spectrometer (EDS) and cyclic voltammetry (CV). The Ti/SnO2-Sb-Ce anode displayed compact, multi-porous morphology and good redox reversibility. The influencing factors such as current density, pH, concentration of Na2SO4, initial MNZ concentration were studied to obtain main factors and optimum conditions. In addition, a preliminary study on the mechanism of the electro-oxidation was carried out. The results demonstrate that chemisorbed oxygen has a dominant role in MNZ removal.