Metal anode instability, including dendrite growth, metal corrosion, and hetero-ions interference, occurring at the electrolyte/electrode interface of aqueous batteries, are among the most critical issues hindering their widespread use in energy storage. Herein, a universal strategy is proposed to overcome the anode instability issues by rationally designing alloyed materials, using Zn-M alloys as model systems (M = Mn and other transition metals). An in-situ optical visualization coupled with finite element analysis is utilized to mimic actual electrochemical environments analogous to the actual aqueous batteries and analyze the complex electrochemical behaviors. The Zn-Mn alloy anodes achieved stability over thousands of cycles even under harsh electrochemical conditions, including testing in seawater-based aqueous electrolytes and using a high current density of 80 mA cm−2. The proposed design strategy and the in-situ visualization protocol for the observation of dendrite growth set up a new milestone in developing durable electrodes for aqueous batteries and beyond. Metal anode instability due to several intrinsic factors limits their widespread use in energy storage. Here, the authors report a 3D alloy anode via a universal alloy electrodeposition approach to overcome the anode instability issues and demonstrate a seawater-based aqueous battery.

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Stable, high-performance, dendrite-free, seawater-based aqueous batteries.

In this work, a facile method was used to synthesize the Zn3(PO4)2/BiPO4 composite photocatalysts with different Bi contents followed by heat treatment at 900 °C for 3 h. The as-prepared samples were studied by a variety of characterization techniques including X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) combined with energy dispersive X-ray diffraction (EDX), Transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and UV–vis diffuse reflectance spectroscopy (DRS). The UV–vis spectroscopy was used to analyze the evolution of Rhodamine B discoloration in presence of the synthesized phosphate photocatalysts. The XRD, SEM-EDX, TEM, DRS and XPS analyses confirmed the formation of heterojunction structure between both materials, during the process of co-precipitation and ulterior heat treatment. The photocatalytic tests showed that photocatalytic ability of the 70% Bi-Zn3(PO4)2 composites was higher than that of pure Zn3(PO4)2 and BiPO4 after 1 h of UV-illumination. The obviously enhanced photocatalytic activity of the 70% Bi-Zn3(PO4)2 sample could be mainly attributed to the formation of the heterojunction, accelerating the separation of photogenerated charge carriers. A plausible mechanism of the photocatalytic degradation of RhB on Zn3(PO4)2/BiPO4 composites is proposed. The reduction in the Chemical Oxygen Demand (COD) revealed the mineralization of dye along with color removal. Thus, it can be suggested that the 70% Bi-Zn3(PO4)2 can serve as a promising photocatalyst in the degradation of organic contaminants under UV light.

Preparation, characterization and photocatalytic degradation of Rhodamine B dye over a novel Zn3(PO4)2/BiPO4 catalyst

Photocatalytic technology utilizing abundant solar light holds great promise to tackle many challenging environmental and energy issues. In recent years, various types of photocatalysts have been developed that are active for environmental purification and hydrogen production. Papers reporting preparation, characterization and photocatalytic testing of binary, ternary and quaternary compounds have been reviewed. The present review focuses on photocatalyst materials which adopt a defect pyrochlore structure. Starting with a brief introduction to semiconductor-based photocatalysts for environmental clean-up and hydrogen generation from water splitting, the development of high-efficiency UV and visible light driven photocatalysts belonging to the defect pyrochlore family is reviewed. The review covers all the defect pyrochlore photocatalysts studied so far, and provides guidance to researchers in this area for further investigation of these materials. © 2015 Society of Chemical Industry

Defect pyrochlore oxides: as photocatalyst materials for environmental and energy applications ‐ a review

A series of 5 mol % Eu3+-doped rare earth (RE) hafnium oxide RE2Hf2O7 (RE = Y, La, Pr, Gd, Er, and Lu) nanoparticles (NPs) have been synthesized, calcinated, and systematically investigated using X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, Fourier transform infrared spectroscopy, and optically excited luminescence. Effects of the A-site RE3+ cation and calcination on the crystal structure of the RE2Hf2O7:5%Eu NPs were distinguished using XRD and Raman studies. Spectroscopic analysis showed that the La2Hf2O7:5%Eu3+ and Pr2Hf2O7:5%Eu3+ possessed ordered pyrochlore structures while the RE2Hf2O7:5%Eu3+ compositions (RE = Y, Er, and Lu) possessed disordered fluorite structure and were thermodynamically stable up to the highest calcination temperature employed in this study (1500 °C); however, a disordered–ordered transition observed in the Gd2Hf2O7:5%Eu3+ composition indicated that it was not thermodynamically stable. Detailed photoluminescence (...

Systematic Studies on RE2Hf2O7:5%Eu3+ (RE = Y, La, Pr, Gd, Er, and Lu) Nanoparticles: Effects of the A-Site RE3+ Cation and Calcination on Structure and Photoluminescence

A text-book of quantitative chemical analysis.

Nano sized defect pyrochlore, KAl0.33W1.67O6 (KAW), is prepared through sol–gel method. Divalent tin-doped KAW is obtained at room temperature by ion exchange method using acidified SnCl2 and parent KAW. These materials are characterized by powder X-ray diffraction, thermogravimetric analysis (TGA), scanning electron microscopy—energy dispersive spectra (SEM-EDS), Raman Spectroscopy and X-ray photo electronic spectroscopy. The composition of tin-doped KAW is obtained from chemical analysis, SEM-EDS and TGA methods and written as Sn0.5Al0.33W1.67O6 xH2O (x = 1.4–1.5) (SnAW). It crystallizes in cubic lattice with space group. The band gap energies are found to be 2.82 and 2.21 eV for KAW and SnAW respectively. The observed reduction in the band gap with the introduction of Sn2+ in defect pyrochlore lattice is due to mixing of 5s state of Sn2+ with O 2p states leading to an upward shift in the valence band. The Raman spectra of these materials gave more bands than the number expected for defect pyrochlores due to substitutional disorder in 16c sites and displacive disorder of A ions. The photoactivity of SnAW is higher compared to KAW.

Synthesis, Characterization and Photocatalytic Activity of KAl0.33W1.67O6 and Sn0.5Al0.33W1.67O6xH2O

A novel series of visible light-sensitive Cu2+, Sn2+, and Ag+-substituted LiMg0.5Ti0.5O2 photocatalysts were synthesized by a facile ion-exchange method and characterized by XRD, UV-Vis diffuse reflectance spectra, scanning electron microscopy equipped with an X-ray energy-dispersive spectroscopy, Brunauer-Emmett-Teller surface area, inductively coupled plasma mass spectrometry, and thermal gravimetric analysis. The characterization results showed that morphology, crystallite size, and surface areas of the ion-exchange products were almost similar to the parent compound. Absorption edges of Ag+-doped (AMT), Cu2+-doped (CMT), and Sn2+-doped (SMT) samples were red shifted remarkably into the visible light region while parent LiMg0.5Ti0.5O2 (LMT) was UV active. Photocatalytic activity of these samples was evaluated by studying the degradation of methylene blue and nitro benzene under visible light irradiation and the stability of all samples during photocatalytic experiment was also investigated. The activity of all photocatalysts was ranked accordingly as SMT ≥ AMT > CMT > LMT. The correlation between photocatalytic properties, band gap energy, rate of recombination of the charge carriers, and amount of ●OH radicals generated during photocatalysis and the underlying reasons were discussed.

Facile Ion‐Exchange Synthesis and Visible Light Photocatalytic Studies of Cu2+, Sn2+, and Ag+‐Substituted LiMg0.5Ti0.5O2

BACKGROUND

Sn-doped metal oxides have attracted considerable attention due to their potential applications in environmental remediation by degrading organic pollutants to less harmful byproducts and hydrogen generation from water splitting. Divalent tin was doped into defect pyrochlore K0.51Sb2.67O6.26 (KSO) to improve its visible light photocatalytic activity.



RESULTS

The Sn-doped K0.51Sb2.67O6.26 (SSO) was obtained from parent KSO by an ion exchange method. The bandgap energy of KSO was reduced from 3.64 to 2.68 eV following Sn2+ doping into the KSO latttice. The photocatalytic activity of KSO and SSO was studied by degradation of methylene blue (MB) and rhodamine B (RhB) under visible light irradiation. SSO showed higher photodegrdation of MB and RhB whereas pristine KSO was almost inactive for the degradation of both dyes.



CONCLUSIONS

The MB and RhB degradation efficiency of SSO was 86 and 53%, respectively. The higher photocatalytic activity of SSO is attributed to more absorption of light energy in the visible region due to lowering of the bandgap energy as well as the generation of •OH radicals during the photocatalytic reaction. Even after a fourth cycle of photodegradation of MB, the photocatalyst (SSO) was found to be stable, with a marginal decrease in the rate of degradation. © 2013 Society of Chemical Industry

Facile ion-exchange synthesis of visible light active Sn-doped defect pyrochlore K0.51Sb2.67O6.26 and study of its photocatalytic activity

KSbWO6 was prepared by sol-gel method. N-doped KSbWO6 (KSbWO6–xNx) was obtained by heating KSbWO6 and urea at 400 °C. Both the compounds are characterized by powder X-ray diffraction (XRD), TEM, SEM-EDS, X-ray photo electronic spectroscopy (XPS), and UV/Vis diffuse reflectance spectroscopy (UV-DRS). A shift in the peak positions of powder XRD and XPS spectra was observed. The band gap energy (Eg) of KSbWO6 and N-doped KSbWO6 was obtained from their diffused reflectance spectra.Eg was reduced from 3.17 eV to 2.56 eV upon nitrogen doping in KSbWO6. The reduction of the Eg is attributed to the lifting of valence band of N-doped KSbWO6, due to the mixing of O 2p states with N 2p states. The photocatalytic activity of both the samples was studied by degradation of methylene blue (MB). The nitrogen doped KSbWO6 shows higher photocatalytic activity compared to that of KSbWO6.

Gundeboina Ravi

Papers

Synthesis, Characterization and Photocatalytic Activity of KAl0.33W1.67O6 and Sn0.5Al0.33W1.67O6xH2O

Facile Ion‐Exchange Synthesis and Visible Light Photocatalytic Studies of Cu2+, Sn2+, and Ag+‐Substituted LiMg0.5Ti0.5O2

Facile ion-exchange synthesis of visible light active Sn-doped defect pyrochlore K0.51Sb2.67O6.26 and study of its photocatalytic activity

Sol-Gel Synthesis and Photocatalytic Study of Visible Light Active N-Doped KSbWO6†

Enhancement of Photocatalytic Activity of Sodium Bismuth Titanate by Doping with Copper, Silver, and Tin Ions