Ammonia (NH3) is a carbon-free fuel and essential for producing chemicals like fertilizer. The conversion of toxic nitrite (NO2-) ions from contaminated water to NH3 in an electrocatalytic system is...

This study reports a novel hydrogel synthesized using only water and the inorganic salts of FeCl 3 .6H 2 O and (NH 4 ) 6 Mo 7 O 24 .4H 2 O, which offers a stable host for various ions (including Li + , Na + , Mg 2+ , Zn 2+ , Mn 2+ , or Ca 2+ ), affording high ionic conductivity. More interestingly, the redox pair Fe 2+ / Fe 3+ of the gel renders considerable pseudo-capacitance, delivering a high volumetric energy density (4.8 mWh cm −3 , based on the one-piece half-cell) and cycling stability. This simple one-piece approach is convenient and effective-by pairing the mineral gel-based half-cell with another matching electrode, a novel type of charge storage device is formed, with the gel serving as one electroactive material, the electrolyte, and the membrane separator. Furthermore, the mineral hydrogel reported here is of low cytotoxicity, self-bondable and healable, and highly resistant against swelling and disintegrating, with no collapse or volume expansion observed even after being soaked in water for 60 days. To our knowledge, this is the first time that mineral hydrogels have been synthesized from all-inorganic agents in a fully biocompatible setting, which also sheds light on the myth-ridden topic of pre-cell evolution in the prebiotic age.

Ammonium (NH4 +) in wastewater is both a major pollutant and a valuable resource. Flow-electrode capacitive deionization (FCDI) is a promising technology for chemical-free and environmentally friendly NH4 + removal and recovery from wastewater. However, the coexisting sodium (Na+) in wastewater, with a similar hydrated radius to NH4 +, competes for the adsorption sites, resulting in low NH4 + removal efficiency. Here, potassium dititanate (K2Ti2O5 or KTO) particles prepared by the electrospray method followed by calcination were mixed with activated carbon (AC) powder to form a novel KTO-AC flow-electrode for selective NH4 + removal over Na+. The mixed KTO-AC electrode exhibits a much higher specific gravimetric capacitance in NH4Cl solution than in NaCl solution. Compared with the pure AC electrode in the FCDI tests on NH4 + removal from synthetic wastewater, 25 wt % KTO addition in the electrode mixture increases the adsorption selectivity from 2.3 to 31 toward NH4 + over Na+, improves the NH4 + removal from 28.5% to 64.8% and increases the NH4 + desorption efficiency from 35.6% to over 80%, achieving selective NH4 + recovery and effective electrode regeneration. Based on DFT calculations, NH4 + adsorption on the K2Ti2O5 (0 0 1) surface is more thermodynamically favorable than that of Na+, which contributes to the high NH4 + adsorption selectivity observed.

Metal hexacyanoferrates have been recognized as superior cathode materials for zinc and zinc hybrid batteries, particularly the Prussian blue analogue (PBA). However, PBA development has been hindered by several limitations, including small capacities (< 70 mAh g−1) and short lifespans (<1000 cycles). These limitations generally arise due to incomplete activation of redox sites and structure collapse during intercalation/deintercalation of metal ions in PBAs. According to this study, the adoption of a hydroxyl‐rich (OH‐rich) hydrogel electrolyte with extended electrochemical stability windows (ESWs) can effectively activate the redox site of low‐spin Fe of the KxFeyMn1‐y[Fe(CN)6]w·zH2O (KFeMnHCF) cathode while tuning its structure. Additionally, the strong adhesion of the hydrogel electrolyte inhibits KFeMnHCF particles from falling off the cathode and dissolving. The easy desolvation of metal ions in the developed OH‐rich hydrogel electrolytes can lead to a fast and reversible intercalation/deintercalation of metal ions in the PBA cathode. As a result, the Zn||KFeMnHCF hybrid batteries achieve the unprecedented characteristics of 14500 cycles, a 1.7 V discharge plateau, and a 100 mAh g−1 discharge capacity. The results of this study provide a new understanding of the development of zinc hybrid batteries with PBA cathode materials and present a promising new electrolyte material for this application.This article is protected by copyright. All rights reserved