Hexavalent chromium (Cr(VI)) contamination represents one of the most persistent and complex environmental challenges of our time. This comprehensive review synthesizes current knowledge across toxicology, environmental geochemistry, analytical chemistry, and remediation technologies to reveal fundamental disconnects between scientific understanding and practical solutions. While research has elucidated molecular mechanisms of Cr(VI) toxicity with remarkable precision – from cellular entry through oxidative damage cascades to genomic instability – this knowledge has not translated into proportionally effective environmental remediation strategies. The analysis reveals that chromium contamination is more complex and persistent than traditionally acknowledged. The reversible nature of chromium redox transformations creates dynamic contamination cycles that resist conventional treatment approaches. Emerging evidence challenges the traditional safe Cr(III) versus toxic Cr(VI) paradigm, suggesting all chromium forms may pose health risks under certain conditions. Critical assessment of current remediation technologies demonstrates that while laboratory studies consistently report high removal efficiencies, these approaches fail to address the vast scale of existing environmental contamination. Most critically, conventional methods focus on transferring chromium between phases rather than implementing circular economy principles that enable recovery and reuse of this valuable element. The review concludes that to address the chromium crisis, it is necessary to move beyond conventional wastewater treatment and adopt prevention-focused strategies that emphasize circular economy principles. Future solutions must prioritize contamination prevention, closed-loop industrial systems, and long-term management rather than pursuit of complete remediation. Only through such realistic assessment and integrated action can we hope to minimize the ongoing impacts of this persistent environmental challenge.

Development of high power devices with improved energy density is a highly desired target for advanced energy storage applications. Herein we propose a new strategy of triply-hybridized supercapacitive energy storage device composed of hybrid battery–supercapacitor negative electrode [Mo₆S₈ (Chevrel-phase)/Ti₃C₂ (MXene)] coupled with positive nanoporous carbon electrode, integrated with novel yet unexplored saturated (14 M) aqueous solution of LiCl. The electrochemical stability window of this electrolyte solution (2.70 V) significantly exceeds the cell voltage (2.05 V) relevant for the asymmetrical (hybrid anode vs. carbon cathode) cells. The aqueous 14 M LiCl solution has far superior characteristics to that of the previously studies 21 m LiTFSI aqueous solution. The paper is also focused on a deep electroanalytical analysis of a peculiar redox/capacitive heterogeneity of hybrid electrodes. It establishes a variety of additivity rules for both differential and integral equilibrium and kinetic characteristics of the charging processes in hybrid electrodes, solving the puzzle of potential distribution of specific electrochemical energy stored the hybrid electrodes. A careful 3-level hybridization design of asymmetric supercapacitive storage devices enabled the integration of battery and supercapacitor materials to get free-standing binderless electrodes suitable for high power/high energy density systems. Studying thoroughly the properties of highly concentrated solutions such as aqueous 14 M LiCl, which are very suitable for different types of supercapacitive devices, combined with profound analyses of the properties of hybrid electrodes, will pave the way for a rational design of very effective devices for energy storage and conversion.

The discovery of the Ti₃C₂T_x compounds (MXenes) a decade ago opened new research directions and valuable opportunities for high‐rate energy storage applications. The unique ability of the MXenes to host various mono‐ and multivalent cations and their high stability in different electrolyte environments including aqueous, organic, and ionic liquid solutions, promoted the rapid development of advanced MXene‐based electrodes for a large variety of applications. Unlike the vast majority of typical intercalation compounds, the electrochemical performance of MXene electrodes is strongly influenced by the presence of co‐inserted solvent molecules, which cannot be detected by conventional current/potential electrochemical measurements. Furthermore, the electrochemical insertion of ions into MXene interspaces results in strong coupling with the intercalation‐induced structural, dimensional, and viscoelastic changes in the polarized MXene electrodes. To shed light on the charging mechanisms of MXene systems and their associated phenomena, the use of a large variety of real‐time monitoring techniques has been proposed in recent years. This review summarizes the most essential findings related to the charging mechanism of Ti₃C₂T_x electrodes and their potential induced structural and mechanical phenomena obtained by in situ investigations.

Reduced water activity in aqueous electrolytes affects oxygen evolution kinetics, expanding electrochemical stability via increased overpotential, but with conductivity and viscosity trade-offs in high-voltage aqueous electrolytes.