Electrochemical Knocking-Down of Zn Metal Clusters into Single Atoms.

Single Atoms Catalysts (SACs) have emerged as a class of highly promising heterogeneous catalysts, where the traditional bottom-up synthesis approaches often encounter considerable challenges in relation to aggregation issues and poor stability. Consequently, achieving densely dispersed atomic species in a reliable and efficient manner remains a key focus in the field. Herein, we report a new facile electrochemical knock-down strategy for the formation of SACs, whereby the metal Zn clusters are transformed into single atoms. While a defect-rich substrate plays a pivotal role in capturing and stabilizing isolated Zn atoms, the feasibility of this novel strategy is demonstrated through a comprehensive investigation, combining experimental and theoretical studies. Furthermore, when studied in exploring for potential applications, the material prepared shows a remarkable improvement of 58.21% for the Li+ storage and delivers a capacity over 300 Wh kg-1 after 500 cycles upon the transformation of Zn clusters into single atoms.

Nanofiltration Ceramic Membranes as a Feasible Two-Pronged Approach toward Desalination and Lithium Recovery.

Ceramic membranes are taking center stage for separation technologies in water treatment. Among them, ceramic nanofiltration membranes are at the forefront of membrane technologies. The desalination of seawater using ceramic nanofiltration membranes is a potential application toward increasing the global water supply and tackling water scarcity. However, while the high fabrication cost poses a challenge to their large-scale applications, high-value separation applications can help to offset the overall cost. In this regard, ceramic nanofiltration membranes can also be explored as a viable option for high-value lithium extraction from the waste seawater brine. In order to determine the potential of nanofiltration ceramic membranes for desalination and lithium recovery from seawater, the current efficiency of salt rejection across various operation parameters must be thoroughly evaluated. Specifically, the interactions between the Donnan exclusion, steric exclusion, zeta potential, and salt concentration play an important role in determining the salt rejection efficiency. Several strategies are then proposed to guide ceramic nanofiltration membranes toward potentially practical applications regarding desalination and lithium recovery.

MAX, MXene, or MX: What Are They and Which One Is Better?

The fast ever-growing interest in transition metal carbonitrides (MXenes) for energy and catalysis is undermined by the undesirable multi-surficial terminations, which severely limit their applications. In contrast, considering the intriguing and tunable electronic structure, rich surface active sites, and high thermal durability, termination-free MXene (MX) hosts a huge possibility for catalysis. As such, recent advances in the evolution from MAX to MXene, and then to MX are overviewed and compared briefly, before concentrating on the unique future of MX in multi-heterogeneous catalysis. This work also looks beyond the fundamental properties of MX and discusses the potential of such materials for applications in multi-electron redox reactions. It is convinced that the potential success of MX in future catalysis is promising. Further extension toward high entropy and single-atom modifications will consolidate the leading position of MX in catalysis.

3D spray-coated gradient profile ceramic membranes enables improved filtration performance in aerobic submerged membrane bioreactor.

Rational design of cross-sectional microstructure in ceramic membranes has shown to improve membrane filtration efficacy without affecting rejection performance. In this work, we adopted 3D spray-coating technique to generate multi-layered membrane layers on macro-porous flat-sheet ceramic supports. The thickness of each layer was controlled by spray-coating cycles, and a gradient membrane layer was rationalized by successively coating three ceramic slurries containing alumina powders of gradually refined particle sizes, followed by co-sintering. Gradient membrane layers on both sides of the various sized flat-sheet ceramic supports were fabricated. Compared to the non-gradient counterpart, the gradient membranes showed both higher pure water flux (at the same TMP) and lower membrane resistance, which clearly evidenced the benefits of gradient profile in the membrane layer. Further, their performance in aerobic membrane bioreactors (AeMBR) was comparably studied for the first time. The treatment performance was not significantly affected by the types of membranes used, while the gradient membrane showed better filtration performance (i.e., a slower rise in TMP). Although the fouling mechanisms were revealed to be similar, the fouling layer in the gradient membrane was composed of a higher percentage of smaller foulants compared to that of the non-gradient counterpart. The observed differences were closely correlated to the larger internal pore structure in the gradient membrane. The present work provides a feasible 3D spray-coating technique for the fabrication of gradient flat-sheet ceramic membranes, and clarifies the benefits in AeMBR for domestic wastewater treatment.

Overcoming the Trade-off between Water Permeation and Mechanical Strength of Ceramic Membrane Supports by Interfacial Engineering.

Porous ceramic membrane supports with high mechanical strength and permeation are required for highly permeable ceramic membranes. The water permeation of a ceramic membrane support is largely dependent on its level of open porosity, which can be however generally detrimental to the mechanical strength. In this work, low-cost kaolin nanoflakes were rationally composited with coarse alumina particles, and multichannel flat-sheet ceramic supports were successfully fabricated by extrusion and subsequent partial sintering. The macroscopic properties, microstructure characteristics, permeability, and mechanical strength of the ceramic membrane supports were systematically established and comprehensively studied. The incorporation of kaolin nanoflakes effectively reduced the sintering temperature to about 1200 °C. An interesting evolution of the pore structure was evidenced with the increase in sintering temperature. Interestingly, the porous ceramic supports prepared at 1400 °C with a nominal pore size of 1.47 µm showed the highest water permeability of 9911.9 ± 357.5 LMHB, and at the same time the flexural strength reached 109.6 ± 4.6 MPa. The much improved permeability was attributed to the unique multilevel pore structures, and the enhanced flexural strength mainly originated from the strongly interfacial bonding, as evidenced by the trans-granular fracture behavior. Also, the ceramic membrane supports exhibited excellent chemical resistance and good removal efficiency for oily wastewater. This work highlights the significant role of interfacial engineering in simultaneously improving the water permeation and mechanical strength, thereby overcoming their trade-off in porous ceramic membrane supports.