O2 Production Rate Research Articles

Enhanced Visible‐Light‐Driven Photocatalytic Overall Splitting of Pure Water in a Porous Microreactor

AbstractPhotocatalytic overall splitting of pure water (H2O) without sacrificial reagent to hydrogen (H2) and oxygen (O2) holds a great potential for achieving carbon neutrality. Herein, by anchoring cobalt sulfide (Co9S8) as cocatalyst and cadmium sulfide (CdS) as light absorber to channel wall of a porous polymer microreactor (PP12), continuous violent H2 and O2 bubbling productions from photocatalytic overall splitting of pure H2O without sacrificial reagent is achieved, with H2 and O2 production rates as high as 4.41 and 2.20 mmol h−1 gcat.−1 respectively. These are significantly enhanced than those in the widely used stirred tank‐type reactor in which no O2 is produced and H2 production rate is only 0.004 mmol h−1 gcat.−1. Besides improved charge separation and interaction of H2O with photocatalyst in PP12, bonding interaction of Co9S8 with PP12 creates abundant catalytic active sites for simultaneous productions of H2 and O2, thus leading to the significantly enhanced H2 and O2 bubbling productions in PP12. This offers a new strategy to enhance photocatalytic overall splitting of pure H2O without sacrificial reagent.

Dual Cocatalysts on Covalent Organic Framework as Charge Transfer Mediator Facilitating Photocatalytic Water Oxidation

AbstractCovalent organic frameworks (COFs) have been regarded as promising photocatalytic materials. However, the sluggish diffusion of photoinduced charges in a single‐component COF remains the obstacles that have to be overcome. Here, we demonstrate a synthesis of a COF bearing dual cocatalysts Co3O4 and Re complex as photocatalyst for water oxidation. The dual cocatalysts are coordinated on the COF, and enable the spatial separation of photoinduced charges. The generated electrons were attracted to Re moiety, while the holes were localized on Co3O4 cocatalyst for water oxidation to produce O2 product. The synergy of dual cocatalysts of COF promote the charge separation and redox reaction. Moreover, hydroxyl radicals generated from the hydration of COF contribute to O−O bond formation, which is the key step of O2 formation. Accordingly, an excellent O2 production rate of 400 μmol g−1 h−1 under visible light irradiation was obtained. This work may pave the way to the development of highly efficient COF photocatalysts for solar energy conversion.

Rational construction of N-containing carbon sheets atomically doped NiP-CoP nanohybrid electrocatalysts for enhanced green hydrogen and oxygen production

The pursuit of sustainable energy production has directed rigorous research in the field of electrocatalysis, particularly for water electrolysis (i.e., hydrogen (HER) and oxygen evolution reactions (OER)). This study discloses the rational synthesis of N-containing carbon sheets atomically doped NiP-CoP nanohybrid (NiP-CoP/NCS) via precipitation/calcination. The fabrication method tailored the physicochemical merits for collective contribution to improved green hydrogen and oxygen, elucidated by surface/bulk characterization and theoretical calculations. Thus, the NiP-CoP/NCS had improved HER activity at lower overpotential (ƞ10 = 197.7/274.6 mV), higher exchange current density (jo = 0.71/0.67 mA/cm2), turnover frequency (TOF = 2.63/1.47 s-1), H2 production rate (3601.63/2519.12 µmol/g/h) and superior stability after 24 h in acid/alkaline media, than NiP/NCS and CoP/NCS. Moreover, NiP-CoP/NCS delivered impressive OER activity at reduced ƞ10 (309.1 mV), and Tafel slope (ba = 58.9 ± 3.0 mV/dec), but higher TOF (3.67 s-1) and O2 production rate (3643.96 µmol/g/h) relative to NiP/NCS and CoP/NCS, besides higher stability for 24 h. These were further proved by theoretical calculations. This work indicates a deeper understanding of the fabrication methods of making efficient electrocatalysts for green and sustainable energy conversion.

Construction of Bi5O7I/Bi3O4Br heterojunction with abundant oxygen vacancies to enhance photocatalytic performance

The low separation efficiency of photogenerated charge carriers is the main impediment to the practical application of photocatalysis. Herein, Bi5O7I nanoparticles with abundant oxygen vacancies (DBOI) were deposited on Bi3O4Br nanosheets (BOBr) to create a novel 0D/2D DBOI/BOBr heterojunction (DBOI-Br) using a facile solution method. The structure of surface oxygen vacancies (SOVs) was demonstrated using HRTEM, low-temperature EPR, and XPS. The effective interface contact between DBOI and BOBr resulted in the establishment of an internal electric field (IEF) and band bending. The photogenerated charge transfer mechanism was validated through in situ irradiated XPS, work function calculation, and ERS measurement. The synergistic effect of IEF, band bending, and SOVs efficiently suppressed the recombination of photogenerated charge carriers, enhancing the photocatalytic activity. Almost 100% of tetracycline, oxytetracycline, levofloxacin, ciprofloxacin, methylene blue, and rhodamine B, as well as 92.3% of phenol, could be decomposed using DBOI-Br under visible light irradiation. The average production rates of H2, O2, and H2O2 were 805, 3800, and 562 μmol h-1 g-1 over 4h, corresponding to quantum efficiencies of 3.67%, 10.4%, and 5.26% at 420nm, respectively. This study introduces a new promising DBOI-Br heterojunction photocatalyst with rich SOVs to enhance the charge separation efficiency for various photocatalytic applications.

Construction of An Artificial Photosynthesis System with A Single CdS QDs-Ferritin Hybrid Molecule.

Establishing artificial photosynthesis systems in a simple but effective manner to mitigate the greenhouse effect and address the energy crisis remains challenging. The combination of photocatalysis technology with bioengineering is an emerging field with great potential to construct such artificial photosynthesis systems, but so far, it has barely been explored in this area. Herein, an artificial photocatalysis platform is constructed with high CO2 conversion and H2O splitting capability by integration of CdS QDs into the intra-subunit interface of H-type ferritin (Marsupenaeus japonicus), a natural ferroxidase through protein interface redesign. The crystal structure of the synthesized CdS QDs with engineered ferritin molecules as bio-templates confirmed the design at an atomic level. Notably, upon absorbing desirable visible light (≈420nm), such a single CdS-ferritin hybrid molecule is able to selectively catalyze the reduction of CO2 into HCOOH (≈90%), meanwhile catalyzing the oxidation of H2O into O2 in an aqueous environment. The O2 production rate reached to 180µmolg-1h-1, and the HCOOH output hit almost 800µmolg-1h-1. This work advances the utilization of the four-helix bundle structure for crafting artificial photosynthesis systems, facilitating the seamless integration of bioengineering and photocatalysis technology.

Self-regenerable oxygen system using microalgae-bacterial consortium for ammonium removal from wastewater

This study investigated self-regenerable oxygen system using microalagae-bacterial consortium for ammonium removal from wastewater and its kinetic modeling based on a combined mechanistic and empirical approach. By mechanistic modeling using a simple microalgal-bacterial Monod model, based on algal growth due to NH4+, NO3− and NO2−, the nitrogen and DO profiles were accurately predicted under different nitrogen conditions (low, medium, and high NH4+ concentrations). The mathematical modeling results showed that sufficient oxygen was available for nitrification at low initial NH4+ ammonium concentration levels, even when dual nitrogen substrate (NH4+–NO2−, NH4+–NO3− or NO2−–NO3−) or all three in combination (NH4+–NO2−–NO3−) were used, compared with high initial ammonium concentration levels. The DO profile was successfully used to monitor N transformation and N uptake in the PSBR based on net O2 uptake rate, O2 production rate, and O2 saturation profile. By empirical modeling of the data obtained, the actual O2 produced by microalgae with the different N species was calculated based on N mass balance and empirical equations. The empirical model further revealed that low NH4+ concentration levels (up to 82.5 mg N/L) favored successful nitrification due to the sufficient production of O2 in the system. However, NH4+ concentration in the range 82.5–132.5 mg N/L affected the nitrification efficiency due to insufficient O2 produced in the system, whereas high ammonium concentration results in nitritation/partial nitrification due to the high demand of O2 by AOB and inhibition in the growth of NOB.

Enhanced Visible-Light-Driven Photocatalytic Overall Splitting of Pure Water in a Porous Microreactor.

Photocatalytic overall splitting of pure water (H2O) without sacrificial reagent to hydrogen (H2) and oxygen (O2) holds a great potential for achieving carbon neutrality. Herein, by anchoring cobalt sulfide (Co9S8) as cocatalyst and cadmium sulfide (CdS) as light absorber to channel wall of a porous polymer microreactor (PP12), continuous violent H2 and O2 bubbling productions from photocatalytic overall splitting of pure H2O without sacrificial reagent is achieved, with H2 and O2 production rates as high as 4.41 and 2.20 mmol h-1 gcat.-1 respectively. These are significantly enhanced than those in the widely used stirred tank-type reactor in which no O2 is produced and H2 production rate is only 0.004 mmol h-1 gcat.-1. Besides improved charge separation and interaction of H2O with photocatalyst in PP12, bonding interaction of Co9S8 with PP12 creates abundant catalytic active sites for simultaneous productions of H2 and O2, thus leading to the significantly enhanced H2 and O2 bubbling productions in PP12. This offers a new strategy to enhance photocatalytic overall splitting of pure H2O without sacrificial reagent.

Novel high-throughput oxygen saturation measurements for quantifying the physiological performance of macroalgal early life stages.

Understanding how macroalgal forests will respond to environmental change is critical for predicting future impacts on coastal ecosystems. Although measures of adult macroalgae physiological responses to environmental stress are advancing, measures of early life-stage physiology are rare, in part due to the methodological difficulties associated with their small size. Here we tested a novel, high-throughput method (rate of oxygen consumption and production; ) via a sensor dish reader microplate system to rapidly measure physiological rates of the early life stages of three habitat-forming macroalgae, the kelp Ecklonia radiata and the fucoids Hormosira banksii and Phyllospora comosa. We measured the rate of O2 consumption (respiration) and O2 production (net primary production) to then calculate gross primary production (GPP) under temperatures representing their natural thermal range. The microplate system was suitable for rapidly measuring physiological rates over a temperature gradient to establish thermal performance curves for all species. The microplate system proved efficient for measures of early life stages of macroalgae ranging in size from approximately 50 μm up to 150 mm. This method has the potential for measuring responses of early life stages across a range of environmental factors, species, populations, and developmental stages, vastly increasing the speed, precision, and efficacy of macroalgal physiological measures under future ocean change scenarios.

Substrate and nutrient manipulation during continuous cultivation of extremophilic algae, Galdieria spp. RTK 37.1, substantially impacts biomass productivity and composition.

The extremophilic nature and metabolic flexibility of Galdieria spp. highlights their potential for biotechnological application. However, limited research into continuous cultivation of Galdieria spp. has slowed progress towards the commercialization of these algae. The objective of this research was to investigate biomass productivity and growth yields during continuous photoautotrophic, mixotrophic and heterotrophic cultivation of Galdieria sp. RTK371; a strain recently isolated from within the Taupō Volcanic Zone in Aotearoa-New Zealand. Results indicate Galdieria sp. RTK371 grows optimally at pH 2.5 under warm white LED illumination. Photosynthetic O2 production was dependent on lighting intensity with a maximal value of (133.5 ± 12.1 nmol O2 mgbiomass -1 h-1) achieved under 100 μmol m-2 s-1 illumination. O2 production rates slowed significantly to 42 ± 1 and <0.01 nmol O2 mgbiomass -1 h-1 during mixotrophic and heterotrophic growth regimes respectively. Stable, long-term chemostat growth of Galdieria sp. RTK371 was achieved during photoautotrophic, mixotrophic and heterotrophic growth regimes. During periods of ammonium limitation, Galdieria sp. RTK371 increased its intracellular carbohydrate content (up to 37% w/w). In contrast, biomass grown in ammonium excess was composed of up to 65% protein (w/w). Results from this study demonstrate that the growth of Galdieria sp. RTK371 can be manipulated during continuous cultivation to obtain desired biomass and product yields over long cultivation periods.

Phytic acid-mediated enhancement of Meyerozyma caribbica biocontrol of Aspergillus carbonarius infection in grape berries through regulation of ROS metabolism

Sour rot, an infection caused by Aspergillus carbonarius is one of the detrimental diseases that damage grape vines after harvest. To investigate the biocontrol of this mycotoxigenic fungus, the current study explored the efficiency of Meyerozyma caribbica pretreated with phytic acid (PA) in reducing sour rot in table grapes through the regulation of reactive oxygen species (ROS) production. The content of hydrogen peroxide (H2O2,), superoxide (O2.−) production rate, and the degree of lipid peroxidation were measured. Furthermore, antioxidant enzymes activities, superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), and enzymes of the ascorbate–glutathione (AsA-GSH) and glutathione peroxidase (GPX) cycles were investigated. Enzymatic activity results of select genes were confirmed using real-time quantitative polymerase chain reaction (RT-qPCR). Meyerozyma caribbica pretreated with 10 μmol/mL PA (YE) was most efficient in reducing sour decay in grape berries as indicated by an 81.1 % reduction in disease incidence and 1.5 mm lesion diameter by the third day. Phytic acid treated M. caribbica showed a significant reduction in the contents of malondialdehyde (MDA), H2O2, and production rate of O2.− which was complemented by a marked rise in ROS scavenging enzymes’ activities. The H2O2 content in YE was the lowest (24.09 nmol/g FW) by the third day and O2.− production rate was about half that of CK; control (4.19 mmol/min.g FW) on the same day. The SOD, POD, and CAT activities were significantly higher in YE treated fruits (6.63, 18, and 6.64 U/mg FW, respectively) compared to the CK by the fifth day. Subsequently, AsA-GSH and GPX cycles also showed higher activity in grapes inoculated with YE compared to other treatments. Genes encoding SOD, POD, CAT, DHAR, GR, and APX were significantly overexpressed in grapes inoculated with YE compared to the CK, yeast alone, and PA treatments. These findings indicate that PA likely enhances the biocontrol efficacy of M. caribbica, leading to the induction of ROS scavenging mechanisms and subsequent mortality of A. carbonarius in table grapes. Consequently, M. caribbica pre-treated with PA holds promise as a potential biological control agent for A. carbonarius in future applications

Net O2 exchange rates under dark and light conditions across different stem compartments.

Woody plants display some photosynthetic activity in stems, but the biological role of stem photosynthesis and the specific contributions of bark and wood to carbon uptake and oxygen evolution remain poorly understood. We aimed to elucidate the functional characteristics of chloroplasts in stems of different ages in Fraxinus ornus. Our investigation employed diverse experimental approaches, including microsensor technology to assess oxygen production rates in whole stem, bark, and wood separately. Additionally, we utilized fluorescence lifetime imaging microscopy (FLIM) to characterize the relative abundance of photosystems I and II (PSI : PSII chlorophyll ratio) in bark and wood. Our findings revealed light-induced increases in O2 production in whole stem, bark, and wood. We present the radial profile of O2 production in F. ornus stems, demonstrating the capability of stem chloroplasts to perform light-dependent electron transport. Younger stems exhibited higher light-induced O2 production and dark respiration rates than older ones. While bark emerged as the primary contributor to net O2 production under light conditions, our data underscored that wood chloroplasts are also photosynthetically active. The FLIM analysis unveiled a lower PSI abundance in wood than in bark, suggesting stem chloroplasts are not only active but also acclimate to the spectral composition of light reaching inner compartments.

A highly stable TiO2/covalent organic framework heterojunction photocatalyst boosting charge transfer for visible-light-driven CO2 reduction

In this study, we present a novel heterojunction photocatalyst (TiO2-TTCOF) boosting charge transfer for visible-light-driven CO2 to CO conversion without photosensitizer or sacrificial agents. The 10% TiO2-TTCOF heterojunction photocatalyst is able to catalyze CO2 conversion, resulting in a highest CO production rate of 139.1 μmol g−1 with a selectivity of 96% and O2 production rate of 73.1 μmol g−1. Additionally, time-resolved fluorescence decay spectra confirmed the heterostructure between TTCOF and TiO2 can promote photoelectron transfer. The ATR-IFTS spectra indicated the photocatalytic reaction pathway.

Coupling Electron Transfer and Redox Site in Boranil Covalent Organic Framework Toward Boosting Photocatalytic Water Oxidation.

The efficient polymeric semiconducting photocatalyst for solar-driven sluggish kinetics with multielectron transfer oxygen evolution has spurred scientific interest. However, existing photocatalysts limited by π-conjugations, visible-light harvest, and charge transfer often compromise the O2 production rate. Herein, we introduced an alternative strategy involving a boranil functionalized-based fully π-conjugated ordered donor and acceptor (D-A) covalent organic frameworks (Ni-TAPP-COF-BF2 ) photocatalyst. The co-catalyst-free Ni-TAPP-COF-BF2 exhibits an excellent ~11-fold photocatalytic water oxidation rate, reaching 1404 μmol g-1 h-1 under visible light irradiation compared to pristine Ni-TAPP-COF (123 μmol g-1 h-1 ) alone and surpasses to reported organic frameworks counterpart. Both experimental and theoretical results demonstrate that the push/pull mechanism (metalloporphyrin/BF2 ) is responsible for the appropriate light-harvesting properties and extending π-conjugation through chelating BF2 moieties. This strategy benefits in narrowing band structure, improving photo-induced charge separation, and prolonged charge recombination. Further, the lower spin magnetic moment of M-TAPP-COF-BF2 and the closer d-band center of metal sites toward the Fermi level lead to a lower energy barrier for *O intermediate. Reveal the potential of the functionalization strategy and opens up an alternative approach for engineering future photocatalysts in energy conversion applications.

Coupling Electron Transfer and Redox Site in Boranil Covalent Organic Framework Toward Boosting Photocatalytic Water Oxidation

AbstractThe efficient polymeric semiconducting photocatalyst for solar‐driven sluggish kinetics with multielectron transfer oxygen evolution has spurred scientific interest. However, existing photocatalysts limited by π‐conjugations, visible‐light harvest, and charge transfer often compromise the O2 production rate. Herein, we introduced an alternative strategy involving a boranil functionalized‐based fully π‐conjugated ordered donor and acceptor (D–A) covalent organic frameworks (Ni‐TAPP‐COF‐BF2) photocatalyst. The co‐catalyst‐free Ni‐TAPP‐COF‐BF2 exhibits an excellent ~11‐fold photocatalytic water oxidation rate, reaching 1404 μmol g−1 h−1 under visible light irradiation compared to pristine Ni‐TAPP‐COF (123 μmol g−1 h−1) alone and surpasses to reported organic frameworks counterpart. Both experimental and theoretical results demonstrate that the push/pull mechanism (metalloporphyrin/BF2) is responsible for the appropriate light‐harvesting properties and extending π‐conjugation through chelating BF2 moieties. This strategy benefits in narrowing band structure, improving photo‐induced charge separation, and prolonged charge recombination. Further, the lower spin magnetic moment of M‐TAPP‐COF‐BF2 and the closer d‐band center of metal sites toward the Fermi level lead to a lower energy barrier for *O intermediate. Reveal the potential of the functionalization strategy and opens up an alternative approach for engineering future photocatalysts in energy conversion applications.

Restricting bioenergetic efficiency enhances longevity and mitochondrial redox capacity in Drosophila melanogaster.

Mitochondria are essential for survival and as such, impairments in organelle homeostasis significantly accelerate age-related morbidity and mortality. Here, we determined the contribution of bioenergetic efficiency to life span and health span in Drosophila melanogaster utilizing the mitochondrial uncoupler BAM15. Life span was determined in flies fed a normal diet (ND) or high fat diet (HFD) supplemented with vehicle or BAM15. Locomotor function was determined by negative geotaxis assay in middle-aged flies fed vehicle or BAM15 under ND or HFD conditions. Redox capacity (high-resolution respirometry/fluorometry), citrate synthase (enzyme activity), mtDNA content (qPCR), gene expression (qPCR), and protein expression (western blot) were assessed in flight muscle homogenates of middle-aged flies fed vehicle or BAM15 ND. The molar ratio of H2O2 and O2 (H2O2:O2) in a defined respiratory state was calculated as a measure of redox balance. BAM15 extended life span by 9% on ND and 25% on HFD and improved locomotor activity by 125% on ND and 53% on HFD. Additionally, BAM15 enhanced oxidative phosphorylation capacity supported by pyruvate + malate, proline, and glycerol 3-phosphate. Concurrently, BAM15 enhanced the mitochondrial H2O2 production rate, reverse electron flow from mitochondrial glycerol-3-phosphate dehydrogenase (mGPDH) to Complex I, mGPDH, and Complex I without altering the H2O2:O2 ratio. BAM15 upregulated transcriptional signatures associated with mitochondrial function and fitness as well as antioxidant defense. BAM15-mediated restriction of bioenergetic efficiency prolongs life span and health span in Drosophila fed a ND or HFD. Improvements in life span and health span in ND were supported by synergistic enhancement of muscular redox capacity.

Planar semiconductor junctions with robust driving forces synergistically orienting direct water splitting

Pure water splitting by charged semiconductors and solar photons to concurrently generate H2 and O2 molecules has gained notable attention due to worldwide clean energy generation and storage. Despite significant advancements, challenges facing severe carrier recombination and sluggish electron transport continue to hinder the intrinsic efficiency of water splitting. Here, we fabricate two-dimensional graphitic carbon nitride-hybridized sulfur thionic polymorphs (CN/S100/S010 junctions) by incorporating photoactive semiconductors within lateral nanosheets. As a result, the charge rectification effect within the coplanar graphitic carbon nitride/S100/S010 junctions is induced by well-designed driving forces: favorable band offsets and cascade polarized surface work functions. During the water splitting process, the photogenerated electrons are sequentially transferred from graphitic carbon nitride to element semiconductor sulfur {100} and subsequently oriented to sulfur {010} facets. This unique behavior of charge migration within CN/S100/S010 photocatalysts contributes to impressive rates of H2 and O2 production, reaching 740 and 363 µmol g−1·h−1, respectively, nearly 13-fold higher than that of the parent carbon nitride. Comprehensive spectroscopic and theoretical analyses confirm the formation of CN/S100/S010 hierarchies with long-lived charge carriers during hydrogen energy production. This work introduces novel avenues for automatically orienting photogenerated carriers and holds promising prospects for clean energy production.

High-efficiency Electroreduction of O2 into H2 O2 over ZnCo Bimetallic Triazole Frameworks Promoted by Ligand Activation.

Co-based metal-organic frameworks (MOFs) as electrocatalysts for two-electron oxygen reduction reaction (2e- ORR) are highly promising for H2 O2 production, but suffer from the intrinsic activity-selectivity trade-off. Herein, we report a ZnCo bimetal-triazole framework (ZnCo-MTF) as high-efficiency 2e- ORR electrocatalysts. The experimental and theoretical results demonstrate that the coordination between 1,2,3-triazole and Co increases the antibonding-orbital occupancy on the Co-N bond, promoting the activation of Co center. Besides, the adjacent Zn-Co sites on 1,2,3-triazole enable an asymmetric "side-on" adsorption mode of O2 , favoring the reduction of O2 molecules and desorption of OOH* intermediate. By virtue of the unique ligand effect, the ZnCo-MTF exhibits a 2e- ORR selectivity of ≈100 %, onset potential of 0.614 V and H2 O2 production rate of 5.55 mol gcat -1 h-1 , superior to the state-of-the-art zeolite imidazole frameworks. Our work paves the way for the design of 2e- ORR electrocatalysts with desirable coordination and electronic structure.

Photo-Driven Quasi-Topological Transformation Exposing Highly Active Nitrogen Cation Sites for Enhanced Photocatalytic H2 O2 Production.

Herein, the exposure of highly-active nitrogen cation sites has been accomplished by photo-driven quasi-topological transformation of a 1,10-phenanthroline-5,6-dione-based covalent organic framework (COF), which contributes to hydrogen peroxide (H2 O2 ) synthesis during the 2-electron O2 photoreduction. The exposed nitrogen cation sites with photo-enhanced Lewis acidity not only act as the electron-transfer motor to adjust the inherent charge distribution, powering continuous and stable charge separation, and broadening visible-light adsorption, but also providing a large number of active sites for O2 adsorption. The optimal catalyst shows a high H2 O2 production rate of 11965 μmol g-1 h-1 under visible light irradiation and a remarkable apparent quantum yield of 12.9 % at 400 nm, better than most of the previously reported COF photocatalysts. This work provides new insights for designing photo-switchable nitrogen cation sites as catalytic centers toward efficient solar to chemical energy conversion.

Single-Atom Zinc Sites with Synergetic Multiple Coordination Shells for Electrochemical H2 O2 Production.

Precise manipulation of the coordination environment of single-atom catalysts (SACs), particularly the simultaneous engineering of multiple coordination shells, is crucial to maximize their catalytic performance but remains challenging. Herein, we present a general two-step strategy to fabricate a series of hollow carbon-based SACs featuring asymmetric Zn-N2 O2 moieties simultaneously modulated with S atoms in higher coordination shells of Zn centers (n≥2; designated as Zn-N2 O2 -S). Systematic analyses demonstrate that the synergetic effects between the N2 O2 species in the first coordination shell and the S atoms in higher coordination shells lead to robust discrete Zn sites with the optimal electronic structure for selective O2 reduction to H2 O2 . Remarkably, the Zn-N2 O2 moiety with S atoms in the second coordination shell possesses a nearly ideal Gibbs free energy for the key OOH* intermediate, which favors the formation and desorption of OOH* on Zn sites for H2 O2 generation. Consequently, the Zn-N2 O2 -S SAC exhibits impressive electrochemical H2 O2 production performance with high selectivity of 96 %. Even at a high current density of 80 mA cm-2 in the flow cell, it shows a high H2 O2 production rate of 6.924 mol gcat -1 h-1 with an average Faradaic efficiency of 93.1 %, and excellent durability over 65 h.

Microalgae as a potential feedstock for biodiesel production in the Philippines: A review

Organic sources of biodiesel, such as microalgae are considered nowadays as potential renewable energy resource. In contrast to higher plants, microalgae have fast growth rate, high photosynthetic efficiency, high biomass productivities, as well as high O2 production and CO2 fixation rate. These organisms can be cultivated using accelerated technologies like open pond and photobioreactors. Extraction of oil and its conversion to methyl esters is of primary importance in biofuel industry. Three well known methods of oil extraction for algal lipids are expellers/press, solvent extraction method and supercritical fluid extraction. These methods are influenced by several operational factors that may have considerable impact on the extraction rate and efficiency. In the Philippines, the current scenario for biodiesel consumption is still expected to increase in the future due to the proposed increase of biodiesel blending as mandated by the Philippine Biofuels Law. Massive research efforts were conducted in search for alternative feedstocks in the Philippines. This led to several studies using third generation feedstock (such as microalgae) for biodiesel production. Based on previous studies, microalgae can be cultivated to engineered systems and is more sustainable (as compared to plants and other microorganisms) since it occupies less land area compared to other feedstocks and it is not consumed as food. Hence, microalgae have the potential as alternative biomass feedstock for a sustainable production of biodiesel in the Philippines with superior quality fuel characteristics.