Search for: All records

Abstract The critical gelation conditions observed in dilute aqueous solutions of multiple nanoscale uranyl peroxide molecular clusters are reported, in the presence of multivalent cations. This gelation is dominantly driven by counterion‐mediated attraction. The gelation areas in the corresponding phase diagrams all appear in similar locations, with a characteristic triangle shape outlining three critical boundary conditions, corresponding to the critical cluster concentration, cation/cluster ratio, and the degree of counterion association with increasing cluster concentration. These interesting phrasal observations reveal general conditions for gelation driven by electrostatic interactions in hydrophilic macroionic solutions. 

Abstract Inorganic salts usually demonstrate simple phasal behaviors in dilute aqueous solution mainly involving soluble (homogeneous) and insoluble (macrophase separation) scenarios. Herein, we report the discovery of complex phase behavior involving multiple phase transitions of clear solution – macrophase separation – gelation – solution – macrophase separation in the dilute aqueous solutions of a structurally well-defined molecular cluster [Mo₇O₂₄]⁶⁻macroanions with the continuous addition of Fe³⁺. No chemical reaction was involved. The transitions are closely related to the strong electrostatic interaction between [Mo₇O₂₄]⁶⁻and their Fe³⁺counterions, the counterion-mediated attraction and the consequent charge inversion, leading to the formation of linear/branched supramolecular structures, as confirmed by experimental results and molecular dynamics simulations. The rich phase behavior demonstrated by the inorganic cluster [Mo₇O₂₄]⁶⁻expands our understanding of nanoscale ions in solution. 

Abstract The evergrowing plastic production and the caused concerns of plastic waste accumulation have stimulated the need for waste plastic chemical recycling/valorization. Current methods suffer from harsh reaction conditions and long reaction time. Herein we demonstrate a non-thermal plasma-assisted method for rapid hydrogenolysis of polystyrene (PS) at ambient temperature and atmospheric pressure, generating high yield (>40 wt%) of C₁–C₃hydrocarbons and ethylene being the dominant gas product (Selectivity of ethylene,S_C2H4 > 70%) within ~10 min. The fast reaction kinetics is attributed to highly active hydrogen plasma, which can effectively break bonds in polymer and initiate hydrogenolysis under mild condition. Efficient hydrogenolysis of post-consumer PS materials using this method is also demonstrated, suggesting a promising approach for fast retrieval of small molecular hydrocarbon modules from plastic materials as well as a good capability to process waste plastics in complicated conditions. 

The escalating challenges posed by extreme climate change and the rapid greenhouse effect have heightened stress and urgency among governments, researchers, and the public. Greenhouse gas (GHG) emissions, particularly carbon dioxide (CO2), have signi昀椀cantly contributed to rising atmospheric temperatures, with agriculture, forestry, and industrial activities accounting for 22 % and 17 % of global emissions, respectively. In 2022, global GHG emissions reached 53.8 Gt CO2eq, underscoring the critical need for net-zero technologies and a circular carbon economy. This review systematically evaluates the ef昀椀ciencies of non-thermal and electrochemical CO2 conversion technologies, including plasma, arti昀椀cial photosynthesis, and electrochemical methods, for achieving net-zero emissions. These advanced technologies offer promising pathways for converting CO2 into value-added chemicals, such as syngas, methanol, and formic acid, while reducing atmospheric CO2 concentrations. However, upscaling these technologies from laboratory to industrial scales presents signi昀椀cant challenges, including high energy consumption, economic feasibility, and environmental impacts. The review highlights the mechanisms of CO2 conversion, economic considerations, and the potential for industrial implementation. Priority research directions are identi昀椀ed, focusing on ecological footprints, green supply chains, and the integration of renewable energy sources. By addressing these challenges, non-thermal and electrochemical CO2 conversion technologies can play a pivotal role in mitigating climate change and advancing toward a sustainable, circular carbon economy. 

Initiating depolymerization at ambient temperature by nonthermal air plasma provides a novel and promising route to convert polymer wastes to valuable small molecules. This study showed that the selectivity of partial oxidation of polyvinyl alcohol (PVA) initiated by nonthermal air plasma can be controlled by the polymer to TiO2 ratio and AC (alternative current) voltage and frequency. Transient responses to applying AC (alternating current) power showed that the CO2 led to the formation of CO, propionaldehyde, and acetaldehyde. Significant formation of propionaldehyde showed that -C-OH in PVA can be directly converted to CH3 in propionaldehyde, unraveling a new reaction pathway in nonthermal plasma chemistry. The selectivity of aldehydes is at the same level as that of CO2. The selectivity of aldehydes was further enhanced by nitrogen plasma while the selectivity toward CO2 was increased in the presence of TiO2. This study demonstrated that ambient nonthermal air plasma could provide a potentially effective approach for the selective conversion of polymers to desired small molecules.