Industrial wastewater in Islamabad has led to serious environmental and human health impacts due to the release of endocrine-disrupting chemicals (EDCs) and volatile organic compounds (VOCs) in the water bodies. The advent of wastewater treatment technologies has led to the development of novel approaches like the use of an electrocatalyst for efficient and safe removal of toxic contaminants from the wastewater. In this study, an efficient tri-metallic NiCoFe2-LDH electrocatalyst was prepared by optimizing the metal ratios in the synthesis process using a co-precipitation method. The catalyst was characterized by various tools such as UV-visible spectroscopy, SEM, EDX, and FTIR. A three-electrode electrochemical system (counter, reference, and working electrodes) was used for electrocatalytic activity and simultaneous removal of EDCs from the wastewater. Wastewater samples were collected from selected locations along the industrial discharge channel (Nullah Lai) in the industrial zone of Islamabad city. The physio-chemical analysis showed significant water pollution, including EDCs, VOC, and heavy metals. The electrochemical treatment using NiCoFe2-LDH demonstrated high efficiency across different scan rates (5 to 50 mV/s) and voltages (−0.02 to 1.6 V); for instance, at 1.6 V, the current density rises from 10 mA/cm2 in Scan 5 to 50 mA/cm2 in Scan 50. Furthermore, COD levels were significantly reduced by 74.9%, from 665.6 mg/L to 166.4 mg/L, after electrochemical treatment with NiCoFe2-LDH. GCMS analysis of organics revealed that the electrochemical process was effective in reducing several EDC- and VOC-related peak groups. Overall, this study highlights the potential of the electrochemical approach for treating EDC-contaminated wastewater and its applicability as a sustainable solution for industrial wastewater treatment.
This critical assessment develops a mechanistic framework for plasma-engineered oxynitride thin films in photoelectrochemical (PEC) water splitting, moving beyond description to predictive understanding. Analyzing 30 peer-reviewed studies (2010–2025) via PRISMA 2020 and a structured reliability framework, we evaluate relationships between plasma conditions, film characteristics, and solar hydrogen generation. Results reveal that plasma power, gas composition, and substrate temperature collectively control nitrogen incorporation, crystallinity, and defect formation. Optimized plasma processing conditions were generally associated with improved photocurrent generation, hydrogen evolution performance, and operational stability relative to thermal synthesis routes across most of the reviewed studies, although the 30-study evidence base is still limited and the proposed power-domain classification should be treated as a preliminary framework requiring validation against additional studies. Mechanistic analysis indicates that moderate plasma energies provide sufficient activation for nitrogen incorporation while minimizing lattice damage and excessive defect formation. A unified conceptual framework is proposed relating plasma parameters, film properties, and PEC performance, providing mechanistic guidance for photoelectrode optimization and future process development. Quality assessment identifies that only 13.3% of studies provide high-confidence evidence (46.7% moderate, 40% low), with most lacking complete plasma diagnostics or long-term stability data, highlighting critical research gaps. The framework establishes that plasma engineering’s transformative potential lies in precise control over the composition–structure–property cascade, offering a reproducible route to high-performance oxynitride photoelectrodes for sustainable hydrogen production.
Catechol 2,3-dioxygenase (C23O) is the rate-limiting enzyme in the meta-cleavage pathway of aromatic compound degradation, yet its functional annotation within the structurally conserved VOC superfamily remains challenging due to high sequence homology. Here, we isolated a catechol-degrading strain from bovine feces and identified it as Bacillus thuringiensis HHY919 via whole-genome sequencing. Genome annotation revealed four VOC genes sharing the same COG annotation (“catechol 2,3-dioxygenase”) but divergent KO annotations (two as glyoxalases and two as C23O), suggesting functional divergence. Using homology modeling and molecular docking, we compared their binding affinities toward catechol and 11 derivatives. All four proteins showed typical meta-cleavage binding energies (−4.9 to −5.4 kcal/mol), with slightly more favorable binding than an ortho-cleavage control. Notably, gene4224 exhibited the broadest and strongest predicted affinities in virtual screening against 212 compounds, particularly for trichlorophenol (−6.0 kcal/mol) and complex natural products (qvina_score ≤ −7.6 kcal/mol). Phylogenetic analysis and docking results jointly identified gene3355 and gene4224 as computationally prioritized C23O candidates, with gene4224 recommended as the top candidate for future enzyme engineering and bioremediation studies. This study provides a computational workflow for resolving functional ambiguity in VOC family enzymes and generating testable hypotheses for experimental validation.
Biochar-supported rare earth oxides are herein assessed as heterogeneous catalysts for the UV-assisted Catalytic Wet Peroxide Oxidation (UV-CWPO) treatment of pharmaceuticals under mild conditions. Catalysts were synthesized by two different pyrolysis methods (activated carbon-assisted oxygen-limited pyrolysis in a muffle furnace, and inert-gas pyrolysis in a tubular furnace under nitrogen flow), and characterized by XRD, SEM, and N2 adsorption–desorption isotherms. Their performance in assisting 385 nm UVA-LED CWPO treatment of acetaminophen (ACE), diclofenac (DCF), and metamizole (MTZ) was assessed under circumneutral pH conditions. The biochar-supported cerium-loaded catalyst prepared by oxygen-limited pyrolysis reported the highest activity, achieving 80% ACE and 70% DCF removals within 120 min of treatment, whereas MTZ was completely removed in less than 10 min, with only 16% of the removal attributable to adsorption. Superoxide radicals dominated the degradation mechanism, and photogenerated holes and hydroxyl radicals contributed moderately. Catalyst stability (minimal activity loss and negligible cerium leaching) was confirmed over five consecutive reuses. Degradation efficiency decreased ≈12–18% because of radical scavenging losses caused by the content of inorganic ions and organic matter in tap, river, and WWTP effluent waters. Treated effluents addressed lower toxicity than untreated solutions, reinforcing the environmental safety of this treatment strategy.
The growing stock of post-consumer waste polycarbonate (PC) causes severe environmental pressure and resource loss, whereas conventional mechanical recycling, landfilling and incineration suffer from material deterioration and secondary pollution. Chemical catalytic recycling enables selective carbonate-ester-bond cleavage for value-added production and serves as a promising circular-valorization strategy for waste PC. This review covers three core technical branches: BPA-targeted catalytic depolymerization, fuel production via hydrodeoxygenation and pyrolysis, and high-value chemical upgrading including reductive depolymerization and direct-upcycling. Representative depolymerization catalysts are critically compared regarding mechanisms, conditions, recyclability and practical performance. We highlight the performance gap between neat model-PC lab tests and impurity-bearing real-world waste PC, and differentiate conventional “depolymerization–isolation–repolymerization” closed-loop workflows from monomer-purification-bypassed direct-upcycling routes. Key technical trade-offs, bottlenecks and scenario-oriented suggestions are summarized to support the lab-to-industrial circular recycling of waste PC toward carbon-neutrality goals.
The catalytic performance of copper-modified strontium titanate-based materials (SrTi1−xCuxO3, where x = 0.02, 0.04, 0.06, and 0.10) in the NH3-SCR and NH3-SCO processes was studied. The catalytic materials were obtained by the modified Pechini method and characterized in terms of structural properties (XRD, XAS), surface composition (XPS), microstructural properties (SEM/EDS, SSA measurements), and reducibility (TPR). Catalytic activity, selectivity to N2, and long-term stability in the NH3-SCR and NH3-SCO processes were experimentally verified. The catalytic materials consisted of agglomerates of nanocrystalline perovskite grains with homogeneously distributed copper, except for the material with the highest copper content. The catalytic activity of these materials was found to be highly dependent on copper loading, with STO_4Cu emerging as the optimal catalyst—the NO conversion in NH3-SCR on the level of 88% and exceptional N2 selectivity (>98%) was obtained at 275 °C, despite an extremely low Cu content (below 2 wt.%). Lower copper content (STO_2Cu) in catalysts appears to limit the low-temperature activity, which correlates with a higher Cu(I) contribution. On the other hand, the higher copper loading (STO_10Cu) triggers their aggregation. Twelve-hour isothermal stability tests confirmed robust long-term performance and stable N2 selectivity for both the NH3-SCR (at 250 °C) and NH3-SCO (at 375 °C) reactions, demonstrating the potential of finely dispersed, low-loading copper perovskites for environmental catalysis.
This study demonstrates a waste-to-catalyst strategy in which nickel ferrite (NFO) first removes Cu(II), Co(II), and Cd(II) from aqueous solutions, and the resulting metal-loaded ferrites are subsequently employed as non-noble-metal electrodes for alkaline methanol oxidation. Pristine NFO achieved removal efficiencies of 74.5% for Cu(II), 72.6% for Co(II), and 68.5% for Cd(II). Among the investigated catalysts, Cu/NFO delivered the most favorable electrochemical performance, with a peak current density of 20.5 mA cm−2, an onset potential of 1.30 V vs. RHE in 1 M KOH containing 1 M methanol, and a fitted charge-transfer resistance of 4.24 Ω. Cu/NFO also retained 97.5% of its current after 12 h and 95.1% after 7000 cycles under the specified durability protocols. The superior response is attributed to the complementary contribution of surface Cu+/Cu2+ chemistry, defect-associated oxygen environments, improved electrochemical accessibility, and the open inter-particle architecture identified by the combined characterization results. The data support a synergistic surface-modification effect, although the contribution of each factor cannot be quantitatively separated by the present experiments. The retained magnetic response further provides a practical basis for investigating magnetic catalyst recovery. Overall, the results establish a materials-level waste-to-catalyst platform for alkaline methanol oxidation and motivate future validation in membrane-electrode assemblies and repeated recovery/reuse cycles.
Selective aerobic oxidation of styrene to value-added oxygenated products remains challenging because of the limited activity and difficult recovery of many homogeneous catalysts. Herein, an N,N′-dihydroxypyromellitimide (NDHPI)-functionalized Cu–Co bimetallic metal–organic framework (MOF), denoted NDHPI/Cu1–Co3–MOF, was constructed through an impregnation strategy to combine NDHPI-derived oxidation activity with accessible sites in a recoverable porous solid. Structural characterization supported the incorporation of NDHPI without loss of the principal crystalline features of the framework. Under the optimized conditions, the material afforded 81.94% styrene conversion with 73.5% selectivity toward styrene oxide at 80 °C under continuous molecular-oxygen supply and solvent-free conditions. The composition- and loading-dependent activity trends support complementary material-level contributions from the introduced NDHPI species and the mixed Cu/Co environment. In one sequence of four consecutive uses, styrene conversion decreased from 81.94% to 64.28%, while styrene oxide selectivity changed from 73.50% to 70.17%.
Photocatalytic wastewater treatment is a promising technology for degrading persistent organic pollutants; however, its optimization remains challenging because photocatalytic performance depends on complex interactions among catalyst properties, operating conditions, and wastewater composition. Machine learning (ML) has emerged as a powerful tool for accelerating catalyst development, predicting photocatalytic performance, and optimizing process parameters. This review critically analyzes recent studies on ML-assisted photocatalytic wastewater treatment, covering supervised learning, ensemble learning, deep learning, and hybrid optimization approaches for predicting degradation efficiency, reaction kinetics, and catalyst performance. Rather than simply summarizing existing studies, the review compares the strengths, limitations, and applicability of different ML models while evaluating the influence of dataset quality, feature engineering, and validation strategies on predictive reliability. Emerging developments in explainable artificial intelligence, physics-informed machine learning, digital twins, and autonomous catalyst discovery are also discussed. Current challenges, including limited datasets, data heterogeneity, model overfitting, lack of standardized benchmarking, and poor transferability to real wastewater systems, are critically examined. Finally, future perspectives emphasizing standardized datasets, interpretable AI, rigorous model validation, and intelligent catalyst design are proposed. This review provides a practical roadmap for integrating artificial intelligence with photocatalysis to accelerate the development of reliable and sustainable wastewater treatment technologies.
Airborne polycyclic aromatic hydrocarbons (PAHs) are toxic pollutants that pose significant risks to human health. In this study, a photocatalyst-based polyacrylamide/zinc oxide (PAM/ZnO) hydrogel composite mesh with an open-mesh architecture was successfully fabricated via photoinduced polymerization of acrylamide, in which ZnO served as both the photoinitiator and photocatalyst. The resulting composite exhibited a three-dimensional interconnected porous structure with ZnO particles uniformly distributed throughout the polyacrylamide hydrogel matrix. The hydrogel exhibited typical swelling–deswelling behavior, reaching an equilibrium swelling ratio of 2.71 within 360 min, along with good water-retention capability. The photocatalytic performance of the PAM/ZnO hydrogel composite mesh was evaluated through the degradation of particulate matter (PM)-bound PAHs generated from incense smoke. The concentrations of two- to five-ring PAHs progressively decreased with increasing ultraviolet irradiation time. Complete degradation of naphthalene was achieved after 4 h of UV irradiation, whereas all detected five-ring PAHs were completely removed after 8 h. Furthermore, the mesh-engineered architecture exhibited excellent air permeability with an exceptionally low pressure drop (<120 Pa), even with multiple mesh layers, enabling energy-efficient continuous air recirculation. These characteristics, together with the photocatalytic degradation of particle-bound PAHs, make the PAM/ZnO hydrogel composite mesh a promising platform for sustainable air purification.
Pharmaceutical compounds, emerging medicinal residues, and personal care products (PPCPs) are ubiquitous in aquatic environments and are causing a serious global environmental problem because of their persistence, bioaccumulation, and harmful effects on the environment and human health. Conventional wastewater treatment technologies are sometimes not capable of removing them completely, causing persistent releases of biologically active micropollutants to surface water, groundwater, and drinking water systems. In this context, biomass-derived catalysts are a promising class of advanced materials for environmental remediation because of their sustainable and cost-efficient nature. The catalysts are composed of bio-residues, such as agricultural residues, forestry wastes, and other bioresources, that have tunable surface chemistry, high porosity, and can be activated and functionalized to increase their catalytic activity. This review summarizes recent advances in biomass-derived catalysts for the removal of pharmaceuticals and PPCPs from water. Special attention is given to synthesis methods, such as pyrolysis, hydrothermal carbonization, chemical activation, heteroatom doping, and metal or metal-oxide hybridization. The catalytic mechanisms of pollutant degradation, including adsorption, radical-based advanced oxidation processes, and non-radical electron-transfer mechanisms, are critically discussed. Moreover, the effect of key operating parameters, catalyst stability, and real wastewater test performance are studied. Sustainability aspects such as green synthesis routes, integration of circular bioeconomy, and life-cycle aspects are also emphasized. Finally, current issues like catalyst deactivation, scaling-up, and the lack of a full mechanistic understanding are identified, and future research avenues are suggested to enable the implementation of efficient, durable, and environmentally friendly catalytic systems for large-scale wastewater treatment applications.
Carbon capture is more and more often seen as a component of an integrated carbon-management system than as a stand-alone separation phase. The practical utility of capture technology depends on the chemical state in which the carbon dioxide is held, the energy and material needs for regeneration, the compatibility of the caught species with downstream catalysis and the lifetime of the resulting carbon-containing product. This paper offers an in-depth framework for integrated CO2 capture and circular carbon use, including catalytic conversion, bio-integrated processes, biomass-derived materials and fuels, hydrogen-enabled routes, mineralization, and artificial intelligence-assisted process design. Reactive capture techniques that convert carbonate, bicarbonate, carbamate, dissolved CO2 or surface-bound intermediates without first generating a purified gas stream are contrasted with sequential capture, purification, compression, transport and conversion. The thermocatalytic, electrochemical, photoelectrochemical and biological conversion pathways are compared against common parameters such as working capacity, conversion rate, selectivity, carbon efficiency, regeneration energy, stability and life-cycle greenhouse gas performance. Special emphasis is given on dual-functional materials, interfacial reactors, bio-integrated methanation, carbon mineralization in construction materials and coupling with renewable hydrogen. The review also discusses how machine learning, molecular screening, process simulation, graph-based data architecture, and digital monitoring could speed up material selection and system optimization. Across all pathways, the central design requirement is not maximum capture capacity alone, but a balanced match among binding strength, transport, catalytic reactivity, product separation, durability, and carbon permanence. A reporting framework and research agenda are proposed to guide credible scale-up and comparison of integrated carbon-management technologies.
Enzymatic browning, primarily catalyzed by polyphenol oxidase (PPO), is a major cause of postharvest losses and quality degradation in fresh-cut fruit and vegetable processing. To control this browning, conventional methods such as sulfite treatment and thermal inactivation have been widely used, yet they increasingly face safety, sensory, and regulatory concerns. Because of this, more attention has been directed toward natural PPO inhibitors from agro-industrial by-products as safer, value-added alternatives. However, current knowledge of PPO inhibition mechanisms and rational inhibitor discovery remains fragmented across the literature, limiting the development of effective and sustainable anti-browning approaches. To address this gap, this review presents an integrated framework that covers (i) the structural and kinetic basis of PPO catalysis at the binuclear copper active site; (ii) the mechanistic classification of reversible and irreversible inhibitors, together with kinetic characterization using IC50, Ki, and nonlinear regression approaches; (iii) computational screening strategies, including molecular docking and molecular dynamics simulations as modern tools for predicting enzyme–inhibitor interactions and prioritizing candidate inhibitors; and (iv) the potential of agro-industrial by-products as renewable sources of natural PPO inhibitors for extending the shelf life of fresh-cut produce. Through this framework, this review provides an integrated perspective to support the rational evaluation and future development of effective, sustainable PPO inhibitors for food processing.
This study focuses on the shaping of ZSM–5-based granules using conventional pseudoboehmite as well as aluminum hydroxynitrate precursors obtained by partial thermal treatment of Al(NO3)3·9H2O. The starting materials and nitrate-derived precursors were characterized by X-ray diffraction, thermal analysis, infrared spectroscopy, scanning electron microscopy, and low-temperature nitrogen adsorption. Model pseudoboehmite systems were used to evaluate the effects of moisture, peptization equivalent, and HNO3 concentration in the initial liquid portion on pore volume, apparent density, shrinkage, and axial and radial crushing strength. Acid peptization showed a strongly non-linear effect: small HNO3 additions increased strength and densification, whereas excess acid promoted structural heterogeneity and granule disintegration during thermal treatment. Even at constant moisture and total acid dosage, strength depended markedly on the initial peptizer concentration. In unpeptized ZSM–5/pseudoboehmite composites, increasing zeolite content reduced pore volume but increased density and strength, indicating formation of a more compact framework. Aluminum hydroxynitrate precursors enabled effective shaping of ZSM–5-containing pastes, demonstrating their potential as alternative binder precursors, while the optimized pseudoboehmite systems provided the most favorable overall balance between porosity and mechanical stability.
The synthetic industry has shortened human lifespans because of environmental contamination. Numerous physicochemical methods can be used to decompose the released organic contaminants, but heterogeneous photocatalysis stands out among them. The creation of a novel sunlight-active heterogeneous photocatalyst, ZVI@MnFe2O4/PTh, for possible degradation of RhB dye is discussed in this study. The nanocomposite was fabricated using the hydrothermal method and in situ polymerization of thiophene. The ternary composite photocatalyst (ZVI@MnFe2O4/PTh) and photocatalysts (ZVI@MnFe2O4 and MnFe2O4/PTh) were well characterized in terms of structure (Fourier transform infrared spectroscopy), morphology (scanning electron microscopy), composition (energy-dispersive X-ray), and crystallinity (X-ray diffraction). UV–visible spectroscopic analysis (Tauc plot) was used to determine the energy bandgaps of catalysts. The characterization study supports the successful assembly of ZVI@MnFe2O4 nanoparticles and polythiophene. To evaluate the photocatalytic performance, the photocatalytically helped degradation of Rhodamine B dye from wastewater was also investigated over the new catalysts. The designed heterojunction enhances photogenerated charge separation and stimulates the photocatalytic process. The proposed study’s findings demonstrated that the novel composite’s sunlight-active photocatalytic effectiveness (99% in 90 min at pH 4) was enhanced against the degradation of Rhodamine B dye. Different models were utilized to predict the reaction’s kinetics, and RSM was utilized as a statistical technique to examine the individual and then interaction effects of the influencing parameters. The RSM results were supported by the numerical values of the optimized parameters, which were pH = 4, H2O2 = 10 mM, and composite dose = 20 mg/50 mL, utilizing a 100 ppm RhB solution.
Poly(ethylene terephthalate) (PET) hydrolases have emerged as promising biocatalysts for closed-loop plastic recycling. Among the most efficient enzymes reported to date, LCC-ICCG exhibits exceptional PET-depolymerization performance under industrially relevant conditions. However, the molecular basis for its superior activity relative to engineered PETases such as FAST-PETase and HotPETase remains incompletely understood. Here, we combine microsecond-scale molecular dynamics simulations, quantum mechanical cluster calculations, pre-reaction-state analysis, noncovalent-interaction mapping, and distortion/interaction activation strain analysis to compare LCC-ICCG with FAST-PETase and HotPETase. The simulations show that LCC-ICCG samples catalytically competent pre-reaction-state geometries more frequently, mainly because V212 reshapes the local environment around the scissile ester. This residue relieves steric congestion, supports weak C–H···O guided substrate preorganization, and reinforces both the Asp-His catalytic dyad and the W190-associated pocket architecture. Density functional theory calculations further indicate that this preorganized active site lowers the acylation barrier to 15.5 kcal/mol by reducing substrate distortion and strengthening transition-state interactions. High-temperature simulations show that LCC-ICCG better preserves near-attack geometries at 350 K, linking thermal robustness to sustained catalytic preorganization. Moreover, reciprocal I208V mutations in IsPETase-derived enzymes enrich pre-reaction-state populations, supporting the transferability of the V212-centered design principle. Overall, these results establish pre-reaction-state stabilization as a key determinant of PET-hydrolase efficiency and provide mechanistic design rules for engineering next-generation PET depolymerases.
Photocatalysis is a promising route for the environmentally friendly destruction of organic pollutants and recycling the polluted water in industrial contexts for future environmental challenges. In this novel research work, the coupling of definite proportions of silver phosphate and g-C3N4 is carried out sonochemically for engineering S-scheme Ag3PO4/g-C3N4 heterojunctions. With the data obtained from a N2-adsorption–desorption isotherm, a diffuse reflectance spectrum, X-ray diffraction, a high-resolution transmission electron microscope and zeta potential measurement, as-synthesized nanocomposites are fully characterized and defined. Successful coupling of Ag3PO4/g-C3N4 heterojunctions was verified given the existence of diffraction peaks of g-C3N4 and Ag3PO4; the shift in the peak position of the DRS spectrum of g-C3N4 from 440 to 463 nm; and the decrease of 68% in the photoluminescence emission peak. The crystalline size of the nanocomposite decreased from 76 to 25 nm, which was ascribed to coupling of Ag3PO4 on g-C3N4 under sonochemical conditions. The as-synthesized nanocomposites exhibited different trends in the destruction of rhodamine B dye. The experimental results indicated that the sample containing 15 weight % of Ag3PO4 degraded 89% of the RhB dye. Precise analysis of reactive radicals species experiments indicated that superoxide radicals and positive roles directed the charge transportation between g-C3N4 and Ag3PO4 semiconductors toward the S-scheme mechanism that produces charge radicals of auspicious redox efficiency.
Developing simple and efficient heterogeneous catalysts for transesterification of dialkyl carbonates with alcohols is very significant for achieving green syntheses of unsymmetrical alkyl carbonates. Here, a set of N-doped carbon material (NCM)-supported iron oxides was prepared for catalytic application in transesterification of diethyl carbonate (DEC) with benzyl alcohol to synthesize benzyl ethyl carbonate (BEC). Various characterization results demonstrated that introducing a small amount of iron salts onto the NCM support generated a number of weak Lewis acidic centers after the impregnation–calcination process. The condition-optimized catalyst named 6.0%Fe2O3/NCM-600 displayed very high catalytic activity, selectivity and stability in the transesterification reaction, showing 95% conversion of benzyl alcohol and 98% selectivity to benzyl ethyl carbonate under mild conditions, much better than iron oxide catalysts supported on other carriers (active carbon, SiO2 and Al2O3). The weak-to-medium Lewis acidic sites derived from the interaction between the highly dispersed Fe2O3 and NCM support were the main active centers, while the neighboring basic N-containing groups of NCM might also have promoted the activation of the reagents, thus synergistically catalyzing the transesterification of DEC with alcohols to generate unsymmetrical alkyl carbonates.
Oxygen bubbles, not catalysis, limit the anode of zero-gap alkaline water electrolysis (AWE) at industrial current densities. Here we compare stainless-steel (SS) mesh (M), felt (F), and a bonded felt–mesh bilayer mounted with the felt facing the Zirfon separator (FM) or reversed (MF) in a zero-gap cell (6 M KOH, 80 °C), bare and Ni-plated. On bare SS, architecture dominates: the felt generates fine bubbles (54 μm) and the mesh coarse ones (109 μm), and the correctly oriented bilayer exploits this contrast—fine generation at the separator, coarse evacuation (95 μm) through the mesh—to deliver 1.85 V at 1.0 A cm−2, whereas the reversed stack is the worst electrode tested, showing voltage fluctuations symptomatic of interfacial gas blanketing. Ni plating improves every architecture (bilayer: 391 → 325 mV OER overpotential; 1.85 → 1.80 V) yet compresses the differences between them. Voltammetry and X-ray photoelectron spectroscopy show why: OER cycling converts the plated Ni into an Fe-incorporated NiFe (oxy)hydroxide—Fe appearing despite a nominally Fe-free bath—whose hydrophilicity shrinks bubbles on every architecture. Architecture and surface chemistry are thus complementary attacks on the same gas-management problem, and stacking orientation is a free design variable that no catalyst can replace. Operando impedance at 1.8 V and an overpotential decomposition price the penalty: flipping the electrode nearly triples the gas-transport overpotential at 1.0 A cm−2, from ≈140 to ≈402 mV, while ohmic and kinetic terms remain nearly untouched.
The performance of CO2 hydrogenation to methanol strongly depends on catalyst structure, which can be effectively regulated through the synthesis method. Herein, different sugars (xylose, glucose, fructose, and sucrose) were utilized as complexing agents in the sol–gel method to prepare Cu/ZnO/ZrO2 catalysts with varying physicochemical properties, thereby enabling the establishment of structure–activity relationships. The catalytic test results showed that the catalyst prepared with the assistance of glucose (CZZ-Glc) exhibited superior catalytic performance, with a STY of 316.87 mg gcat−1 h−1, CO2 conversion of 12.44%, and methanol selectivity of 59.36% at 240 °C, 3 MPa, and GHSV = 12,000 mL gcat−1 h−1. Structural characterizations revealed that the CZZ-Glc catalyst had a smaller particle size and a higher Cu surface area, which strengthened the interactions between active phases. Additionally, XPS results revealed that more oxygenated carbon groups (C–O and C=O) were present on the CZZ-Glc catalyst. Both features could facilitate H2 spillover, leading to an increased concentration of surface *H species. In situ DRIFTS experiments revealed that CO2 hydrogenation to methanol over the obtained catalyst followed the formate pathway, and that hydrogenation of adsorbed CO2 and intermediates was obviously promoted on the CZZ-Glc catalyst. These results highlight the importance of synthesis strategy in regulating catalyst structure and provide new insights into the development of high-performance catalysts for CO2 hydrogenation to methanol.
