Halotolerant enzymes are promising biocatalysts for industrial applications due to their ability to function under high salinity and temperature conditions that typically inactivate conventional enzymes. This is particularly relevant for biomineralization-based carbon capture, where carbonic anhydrases (CAs) catalyze the reversible hydration of CO2 but often lack stability in harsh environments such as brine. Here, α-CA genes from three halotolerant bacteria, Aeromonas hydrophila (AhCA), Halomonas binhaiensis (HbCA), and Roseibium salinum (RsCA), were cloned and expressed, and the corresponding enzymes were purified and characterized. Enzymatic activity was evaluated following incubation under different conditions: NaCl concentrations (0–4 M), temperatures (30–80 °C), and divalent metal ions. AhCA and RsCA retained high activity under elevated salinity, with RsCA exhibiting pronounced salt activation after incubation at 4 M NaCl, whereas HbCA displayed comparatively lower salt tolerance but greater thermostability, maintaining activity after incubation at 80 °C for 1 h. Co2+ and Mg2+ produced the strongest activation for AhCA and RsCA, respectively, with metal-dependent effects varying considerably among the three enzymes. Molecular dynamics simulations performed at different NaCl concentrations revealed enhanced structural stability of RsCA under saline conditions, consistent with its superior catalytic performance. A surface physicochemical analysis identified an extensive negatively charged surface characteristic of salt-adapted proteins. Together, these findings identify RsCA as a candidate for further evaluation and provide structural insight into the molecular basis of halotolerance in α-CAs.
Cerium (Ce)-incorporated carbon catalysts, particularly Ce catalysts with Ce–N active sites supported by carbon, have emerged as promising alternatives to noble metal-based catalysts for electrocatalyzing the oxygen reduction reaction (ORR). However, most carbon-supported Ce catalysts featuring Ce–N active sites remain at the proof-of-concept stage, with challenges in synthesis, including the lack of facile synthesis strategies compatible with scalable production. Herein, we present a simple and direct method for preparing Ce-incorporated carbon catalysts by carbonizing a mixture of vital wheat gluten, a type of renewable biomass, and Ce-doped zeolitic imidazolate framework-8. The optimized catalyst exhibits a half-wave potential of 0.82 V and good stability in an alkaline electrolyte. Structural and electrochemical analyses indicate that both CeO2 nanoparticles and Ce–N moieties exist in the obtained catalyst, while the Ce–N moieties are responsible for its efficient ORR activity. A zinc-air battery based on this catalyst delivers a higher peak power density and better durability (90 h) than one based on Pt/C. These results should pave the way for the biomass-assisted synthesis of Ce-incorporated carbon catalysts for ORR, providing a foundation for future scalable production.
Photocatalytic water treatment using titanium dioxide (TiO2)-based nanomaterials has emerged as a promising green technology for removing organic and inorganic contaminants. However, the translation of laboratory-scale photocatalysts into industrial applications remains limited by material complexity, synthesis scalability, and process integration. This study presents a systematic review combining bibliometric and patent analyses to evaluate the evolution of TiO2-based photocatalysis for water remediation from 2006 to 2025. Following PRISMA 2020 guidelines, a Scopus search identified 1402 publications, from which 152 representative studies were selected for detailed qualitative analysis. Bibliometric mapping using VOSviewer revealed four major thematic clusters: hybrid materials for advanced photocatalysis; biopolymers and membrane-based water treatment; advanced TiO2 nanostructures; and advanced synthesis methods for TiO2 nanomaterials. Patent analysis of 80 representative patent families from the Orbit (Questel) database revealed a 375% increase in patent activity over the last decade, with China and India accounting for approximately 80% of global patent activity. Overall, the field has evolved from conventional TiO2 nanoparticles toward multifunctional architectures, including ternary composites, S-scheme heterojunctions, plasmonic systems, and defect-engineered photocatalysts. Nevertheless, conventional multistep synthesis routes, particularly sol–gel and hydrothermal methods, remain dominant, while scalable approaches such as flame spray pyrolysis (FSP) and ultrasonic spray pyrolysis (USP) are scarcely represented in both scientific and patent landscapes. These findings indicate that future progress will depend less on increasing material complexity and more on scalable, sustainable, and economically viable manufacturing strategies capable of enabling industrial water-treatment applications and accelerating reliable technology transfer, long-term stability, and validation in real wastewater treatment matrices.
Herein, value-added iron oxide nanostructures are successfully synthesized directly from industrial steel mill scale via a simple precursor-free planetary ball milling technique for sustainable hydrogen production and environmental remediation. Comprehensive XRD analysis confirms heterogeneous crystalline phases comprising wüstite, magnetite, and hematite. The waste-derived catalysts demonstrate robust bifunctional electrocatalytic activity toward HER and OER in alkaline media, achieving low overpotentials of 342 and 356 millivolts at ten milliamperes per square centimeter for the hydrogen and oxygen evolution reactions, respectively, alongside favorable Tafel slopes and exceptional long-term operational stability. Furthermore, under natural sunlight, the nanostructures achieve efficient photocatalytic degradation of methylene blue, attaining 86.4 and 89.7 percent degradation efficiencies for 15 and 30 milligrams of catalyst. This comprehensive study successfully converts secondary metallurgy industrial byproducts into highly cost-effective multifunctional nanomaterials, thus presenting an exceptionally promising dual-purpose pathway for green hydrogen generation coupled with advanced industrial wastewater purification and environmental pollution control.
Bioinspired coordination engineering can couple photocarrier delivery to peroxide activation, but charge separation and disappearance of a parent pollutant do not identify the operative catalytic state or establish detoxification. This Review examines photoassisted H2O2 and peroxymonosulfate (PMS) activation at single-atom sites through an evidence chain linking light-dependent charge occupation, dynamic coordination, intermediate identity, and carbon and toxicity outcomes. A coordination motif is termed bioinspired only when an enzyme-analogous function—first-shell redox control, distal proton transfer, regulated molecular access, or coupled charge delivery—is identified and subjected to a discriminating test. Direct light/peroxide/substrate studies are distinguished from dark catalysis and peroxide production studies. Peroxydisulfate (PDS) and peracetic acid (PAA) are considered mechanistic boundary cases: principles of site accessibility and evidence quality may transfer, whereas specific intermediates, rate laws, and oxygen sources require independent validation. The discussion evaluates spectroscopic and kinetic tests that separate diffusing radicals, singlet oxygen, bound metal–oxygen states, and interfacial electron transfer. It further specifies how photon flux, oxidant consumption, competitive water matrices, elemental release, carbon balance, and effect-based bioassays should be reported before performance or safety is inferred. The outcome is a testable framework for relating the photo-populated working site to treatment-relevant selectivity.
