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Hydrogen is increasingly viewed as a game‐changer in the clean energy sector. Renewable hydrogen production from water is industrialized by integrating water electrolysis and renewable electricity, but the current cost of water‐born hydrogen remains high though. An ideal scenario would be to produce value‐added chemicals along with hydrogen so the cost can be partially offset. Herein, facilitated bio‐hydrogen extraction and biomass‐derived chemical formation from sugar‐derived 5‐hydroxymethyfurfural (HMF) were achieved via the in‐situ transformation of cobalt‐bound electrocatalysts. The cyanide‐bound cobalt hydroxide exhibited a low voltage at 1.55 V at 10 mA cm−2 for bio‐hydrogen production, compared with an iridium catalyst (1.75 V). The interaction between the biomass intermediate and the cyanide ligand is suggested to be responsible for the improved activity. [ABSTRACT FROM AUTHOR]

Pulsed electrodeposition has been introduced to deposit ultrathin flakes of Co3O4 nanocrystals on ZnO nanorods. By fixing the seeding process, the scaffolding function of ZnO nanorods was studied by varying deposition times (30 s, 60 s, and 90 s) of Co3O4 at a nucleation current of −1.0 mA cm−2. The amount of deposited Co3O4 has a strong influence on the oxygen evolution performance with ZnO scaffolds. To deliver a current density of 10.0 mA cm−2 in neutral solutions (0.5 M K2SO4), the presence of ZnO scaffold electrodes negatively shifted the overpotential by ∼200 mV. In particular, the Co3O4/ZnO hybrid nanostructured electrode (60 s) exhibits the lowest onset potential of 1.5 V (vs. reversible hydrogen electrode, RHE). Electrochemical impedance spectra and double layer capacitance showed that the enhanced oxygen evolution activities originated from the improved charge transfer capability and the increased electrochemically active interface between Co3O4 and ZnO. ZnO nanorods arrays serve as an effective scaffold for highly dispersed pulsed‐electrodeposited Co3O4. The increased electrochemically active area at the intimate interface between Co3O4 and ZnO accounts for the material's excellent performance in the oxygen evolution reaction. [ABSTRACT FROM AUTHOR]

Abstract: Developing highly efficient and earth‐abundant electrocatalysts for the oxygen evolution reaction (OER) is critical in overall water splitting technology. Among all transition‐metal‐based materials, NiFe‐based electrocatalysts have been regarded as the most promising substitute to commercial noble metals in alkaline conditions. To overcome their leaching problem and improve intrinsic stability without compromising activity, we report a NiFe alloy covered with a discrete N‐doped graphitic shell for the OER. The alloy core@discrete graphitic shell structure exhibits enhanced OER activity and stability with a low onset potential of 1.48 V, reduced overpotential of 320 mV@10 mA cm−1, and small Tafel slope value of 41 mV dec−1, which is superior to Ir/C. It is believed that the nitrogen doping, a discrete graphitic shell, and a mesoporous structure work in harmony to enhance the OER performance. [ABSTRACT FROM AUTHOR]

This paper reports the effects of pre-oxidation processes including ozone and ultraviolet (UV) irradiation prior to chloramination on microbiologically assisted monochloramine decay. Water samples with varying water qualities were pre-oxidated by ozone and UV irradiation, followed by determination of chemical and microbiological monochloramine decay ( F m ). Both ozone and UV could effectively improve the reduction of microbial-like compounds responsible for monochloramine decay in treated water samples. Reductions in F m values were observed for ozone contact times (Ct) greater than 5 mg min/L and UV doses greater than 30 mJ/cm 2 . However, UV was less effective than ozone in reducing F m values in raw water samples. Complete removal of the microbiological component of the decay for raw water samples was not found either with ozone (even with Ct of 50 mg min/L) or UV (even with UV dose of 120 mJ/cm 2 ). The effects of pre-oxidation processes on chemical (k c ) and microbial (k m ) decay coefficients were assessed. Increasing both ozone Ct and UV dose ahead of chloramine did not affect the chemical decay component, but they changed the microbiological component of decay. Changes in organic matter after ozonation were also characterized using three-dimensional fluorescence excitation–emission matrix (3D-FEEM) spectroscopy, and correlations between 3D-FEEM spectroscopy results and F m values were found. Intensities of humic-like, fulvic-like, microbial protein-like and aromatic protein-like substances were reduced by pre-ozonation. Based on the 3D-FEEM results, we can confirm that the slowdown of monochloramine decay rate is due to the reduction of marine humic-like substances and soluble microbial protein-like compounds by pre-ozonation. [ABSTRACT FROM AUTHOR]

Abstract: Visible light pre‐treatment has been found to be capable of enhancing the catalytic oxygen activation on AuPt/TiO2 by up to seven times. Visible light pre‐treatment exploits the localized surface plasmon resonance effect of Au to generate free electrons, which are transferred to the Pt active sites. The electron transfer was evident from a change in Pt speciation observed from X‐ray photoelectron spectroscopy, showing the presence of PtO after visible light pre‐treatment. Photoluminescence spectroscopy was used to reveal the bimetallic synergistic enhancement, as indicated by an overall decrease in the charge recombination rate. Further examination revealed that a good bimetallic interaction is necessary to achieve the enhancement by visible light pre‐treatment. Weak bimetallic interaction, such as the occurrence of element segregation in the bimetallic alloy, inhibits electron transfer from the Au to the Pt and increases electron recombination rates, diminishing the degree to which visible light pre‐treatment improves catalytic performance. [ABSTRACT FROM AUTHOR]

Abstract: Natural zeolite coated with titanium dioxide (TiO2) was used as an adsorbent to rapidly remove humic acid (HA) from an aqueous solution. Coating TiO2 onto zeolite markedly improved its efficiency in adsorbing HA: most of the bulk organic matter (80%) could be removed within 5min of adsorption by the zeolite/TiO2 particles at neutral pH, whereas less than 20% was removed by bare zeolite alone. In addition, immobilisation of TiO2 onto zeolite permitted easier separation of the adsorbent from the treated water. Photocatalytic properties of TiO2 were exploited for the regeneration of the adsorbent. The adsorbent was shown to be readily regenerated by photocatalytic oxidation and was still effective in removing HA after 5 adsorption/regeneration cycles. These results indicate that TiO2-coated zeolite can be a very attractive adsorbent for the rapid removal of HA from aqueous solutions. [Copyright &y& Elsevier]

Abstract: The pyrophoricity of Cu/ZnO-based and Pt-based catalysts was studied during oxidative shut-down/start-up of the low-temperature water-gas shift (LT-WGS) reaction to assess whether these catalysts are suitable for fuel cell application. The Cu/ZnO-based catalysts were observed to display high levels of pyrophoricity manifested as a sharp temperature rise of the catalyst bed upon air introduction. This promoted severe sintering of the bulk and metallic phases of the catalyst facilitating catalyst deactivation. No pyrophoricity was observed for any of the Pt-based catalysts; however, sintering of the metallic phase in Pt/TiO2 and Pt/ZrO2 persisted, leading to a decrease in activity. It was likely that the sintering of Pt occurred during LT-WGS operation itself. In contrast, Pt/CeO2 was the only catalyst which retained its activity, displaying no loss in specific surface area or metal dispersion throughout the entire process making it the most suitable candidate of the materials investigated for fuel cell systems. Temperature-programmed oxidation studies indicated deactivation by the oxidative shut-down/start-up operation did not result from the build-up of carbonaceous species. [Copyright &y& Elsevier]

Abstract: 1,4-Dioxane, is a synthetic organic compound used widely throughout industry as a solvent. 1,4-Dioxane causes liver damage and kidney failure and has been shown to be carcinogenic to animals, and is a potential carcinogen to humans. Its recalcitrant nature means that conventional water treatment methods are ineffective in removing it from water. A class of technologies called advanced oxidation technologies has been shown to completely mineralise 1,4-dioxane. In this study the effects of pH on TiO2 photocatalysis reactor systems were investigated. pH was found to significantly affect the efficiencies of these processes with neutral pH conditions the most effective. [ABSTRACT FROM AUTHOR]

Abstract: This study compares the photocatalytic (PC) and photoelectrocatalytic (PEC) oxidation of glucose by Pt–TiO2 films under similar conditions. The overall oxidation efficiency of the PEC process was better than the PC process, for both TiO2 and Pt–TiO2 films. The Pt deposits enhanced the PEC oxidation efficiency of glucose at low cathodic (−0.1V) and low anodic potential bias (+0.1V). As the applied anodic bias was increased to >+0.5V, the undoped-TiO2 films outperformed their Pt–TiO2 counterparts. This suggests that in the studied systems, at an anodic bias of >+0.5V, more holes were available for the oxidation of glucose on the surface of TiO2 compared to Pt–TiO2 films. In the PEC systems, above a certain applied bias, Pt deposits may have a detrimental effect on the performance of a PEC system because the Pt deposits could merely block the surface of TiO2 (particularly at the highest Pt loadings). Lower measured photocurrents from Pt–TiO2 films compared to undoped-TiO2 and a decrease in the photocurrent as the Pt loading increased corroborate this postulation. [Copyright &y& Elsevier]

In this study, two different crystallographic phases of bismuth molybdate, α-Bi 2 Mo 3 O 12 and γ-Bi 2 MoO 6 were synthesized hydrothermally. A series of Bi 2 Mo 3 O 12 /Bi 2 MoO 6 heterostructures with different phase ratios were readily prepared by tuning the concentration of the molybdenum precursor while retaining the same bismuth precursor concentration. The Bi 2 Mo 3 O 12 /Bi 2 MoO 6 heterojunction was found to substantially enhance the photocatalytic water oxidation capability relative to neat Bi 2 Mo 3 O 12 and Bi 2 MoO 6 . The Bi 2 MoO 6 and Bi 2 Mo 3 O 12 were found to possess a complementary band alignment between which enabled the charge transfer process across the heterojunction interface. Ag and MnO x photodeposition was conducted on the heterostructures to affirm the charge transfer direction between the two crystal phases. Under visible light irradiation, photogenerated holes transfer from the active Bi 2 MoO 6 phase to the inactive Bi 2 Mo 3 O 12 , suggesting efficient charge separation occurs between the two components, explaining the better photocatalytic performance. [ABSTRACT FROM AUTHOR]

Although advanced oxidation processes (AOPs) such as photoelectrochemical oxidation (PECO), electrochemical oxidation (ECO) and photocatalytic oxidation (PCO), have shown potential for wastewater treatment, their application in urban stormwater has rarely been studied. This paper explored their major degradation mechanisms and possible degradation pathways of herbicides for stormwater applications (with treatment difficulty compared with wastewater). PECO and ECO showed excellent removal performance for diuron (100 %) and moderate for atrazine (around 35 %) under a relatively low potential (2 V). Superoxide radical (·O 2 -) has been found to be the dominant reactive species. Besides, there is evidence to indicate that hydroxyl radical (·OH) and free chlorine (·Cl) also support the degradation reactions. Up to 11 possible intermediate products have been identified during both diuron and atrazine degradation processes under PECO operation. Based on the proposed possible degradation pathways, the intermediates presented during PECO are species with further oxidation. As evidenced by the undetected species of more oxidized intermediates for ECO and PCO, some further degradation steps are missing, which demonstrate their lower oxidation capacity leading to incomplete decomposition of stormwater herbicides. Thus, PECO has a great potential to be developed into a passive stormwater degradation system due to its strong oxidation potential. [Display omitted] • Carbon fiber anode supported stormwater herbicides removal via low voltage. • Superoxide radicals were found as the major reactive species in oxidation process. • Degradation pathways of herbicides were proposed for advanced oxidation processes. • Intermediate products results suggest detoxification effect during the process. [ABSTRACT FROM AUTHOR]

Abstract: The photocatalytic activity of sodium titanate (Na1.48H0.52Ti3O7), sodium hexatitanate (Na2Ti6O13), and hydrogen titanate (H2Ti3O7) nanoribbons and anatase TiO2 nanorods were compared for water splitting, oxalic acid photodegradation and H2 and O2 generation using sacrificial agents. The intrinsic properties of the materials were found to affect their performance depending on the particular reaction system. The Na2Ti6O13 nanoribbons, in the presence of RuO2 co-catalyst, outperformed the anatase nanorods, for the water splitting reaction, generating over 10 times more H2/O2. This was thought to derive from their tunnel-like structure which provided better electron/hole separation when compared with TiO2. However, the efficient holes and electrons scavenging in the presence of sacrificial agents, methanol or AgNO3, to generate H2 or O2, respectively, overwhelmed the tunnel-like structure effect. In this case photoactivity was governed by the crystal structure, with observed decreasing activity in the order TiO2>Na2Ti6O13>H2Ti3O7∼Na1.48H0.52Ti3O7, and by the band gap of the semiconductor which determined its capacity to absorb photons in producing electron/hole pairs. [Copyright &y& Elsevier]

Abstract: The photocatalytic degradation of malic acid was studied under ambient conditions in an aqueous TiO2 suspension. The results demonstrated the presence of four distinct mineralization rate variations over the course of its degradation. Differences in the mineralization rate were governed by the dominant intermediate present in the solution at that time. Initial mineralization was rapid (∼175μgC/min) resulting from the swift extraction of a carbon from strongly adsorbed malic acid via the photo-Kolbe mechanism. The mineralization rate then slowed down (∼50–70μgC/min) with the continued formation of an intermediate product (believed to be malonaldehydic acid), malonic acid and acetic acid in the solution. The findings provide greater insight into the photocatalytic degradation mechanism, illustrating the importance of intermediates and their attributes in relation to the overall rate of organic removal. [ABSTRACT FROM AUTHOR]

Abstract: Active sites responsible for the preferential oxidation of carbon monoxide were investigated using 4wt.% Cu–CeO2 catalysts prepared by flame spray pyrolysis. Surface redox properties of the catalyst were assessed using a series of temperature-programmed reduction (CO, H2 and mixed) experiments, as well as operando infrared spectroscopy. It was demonstrated that CO and H2 react at identical surface sites, with CO2 formation proceeding simultaneously via three distinct Cu n +–CO carbonyl species. The origin of high catalytic selectivity towards CO at below 150°C stems from the carbonyl stabilization effect on the catalyst surface, preventing adsorption and subsequent oxidation of H2. Under non-selective conditions at higher temperatures, a gradual red-shift and loss of intensity in the carbonyl peak was observed, indicating reduction of Cu+ to Cu0, and the onset of an alternate redox-type oxidation mechanism where CO and H2 compete for the oxidation sites. These results for Cu–CeO2 suggest that improved low-temperature catalytic activity will only be achieved at the expense of reduced high-temperature selectivity and vice versa. [ABSTRACT FROM AUTHOR]

Abstract: The effect of TiO2 photocatalytic oxidation on the natural organic matter (NOM) properties of two Australian surface waters were quantified using UV–vis spectroscopy, high performance size exclusion chromatography (HPSEC) with a multi-wavelength UV detector, liquid chromatography with organic carbon detector (LC-OCD), and trihalomethane formation potential (THMFP) analyses. Both the UV absorbance at wavelengths greater than 250nm and dissolved organic carbon (DOC) content decreased significantly with treatment, although complete mineralization of NOM could not be achieved. Multi-wavelength UV detection of HPSEC analysis was shown to be useful to display further changes to NOM composition and molecular weight profiles because the organic molecules was transformed into compounds that absorb weakly at the typical detection wavelength of 250–260nm. The multi-wavelength HPSEC results also revealed that photocatalytic oxidation yields by-products with a low aromaticity and low molecular weight. The LC-OCD chromatograms indicated that low molecular acids and neutral compounds remained after photocatalytic oxidation. Those groups of compounds did not seem to contribute significantly to the formation of trihalomethanes. [Copyright &y& Elsevier]

In this study, changes in the physical and structural properties of natural organic matter (NOM) during titanium dioxide photocatalytic oxidation process were investigated using several complementary analytical techniques. Potential of the treated water to form trihalomethanes (THMs) and haloacetic acids (HAAs) was also studied. High-performance size exclusion chromatography analysis showed that NOM with apparent molecular weights of 1-4 kDa were preferentially degraded, leading to the formation of lower molecular weight organic compounds. Resin fractionation of the treated water demonstrated that the photocatalytic oxidation changed the affinity of the bulk organic character from predominantly hydrophobic to more hydrophilic. Short chain aldehydes and ketones were identified by mass spectroscopy as one of the key degradation products. The addition of hydrogen peroxide to photocatalysis was found to increase the degradation kinetics but did not affect the reaction pathway, thus producing similar degradation end products. The amount of THMs normalized per dissolved organic carbon (specific THM) formed upon chlorination of NOM treated with photocatalytic oxidation was reduced from 56 to 10 μg/mg. In contrast, the specific HAAs formation potential of the treated water remained relatively unchanged from the initial value of 38 μg/mg, which could be due to the presence of hydrophilic precursor compounds that were formed as a result of the photocatalytic oxidation process. [ABSTRACT FROM AUTHOR]

• Advanced oxidation processes demonstrate effective degradation performance. • Boron-doped diamond can undergo long-term operation under challenging voltage. • Oxidation process can be improved by voltage increase, not for catalysts loading. • Solar thermal effect has a positive effect for advancing the system performance. • The results suggest the potential validation fully supported by solar energy. The solar driven advanced oxidation process (AOP) has the potential to be developed as a passive stormwater post-treatment method. Despite its widespread studies in wastewater treatment, the applicability of the process for micropollutant removal in stormwater (which has very different chemical properties from wastewater) is still unknown. This paper investigated the feasibility of three different AOP processes for the degradation of two herbicides (diuron and atrazine) in pre-treated stormwater: (i) photoelectrochemical oxidation (PECO), (ii) electrochemical oxidation (ECO), and (iii) photocatalytic oxidation (PCO). The durability of different anode materials, the effects of catalyst loading, and solar photo- and thermal impacts under different applied voltages were studied. Boron-doped diamond (BDD) was found to be the most durable anode material compared to carbon fiber and titanium foil for long-term operation. Due to the very low electroconductivity of stormwater, a high voltage was required, causing severe oxidation of the carbon fiber material. PECO achieved the best degradation results compared to ECO and PCO, with over 90% degradation of both herbicides in 2 h under 5 V, following a first-order decay process (with a half-life value of 0.40 h for diuron and 0.58 h for atrazine). The voltage increase had a positive impact on the oxidation processes, with 5 V found to be the optimal applied voltage, while catalyst loading had a negligible effect. Interestingly, the solar thermal effect plays a dominant role in enhancing the performance of the PECO process, which indicates the potential of integrating a photovoltaic chamber with a PECO system to harness both the light and heat of solar energy for stormwater treatment. Image, graphical abstract [ABSTRACT FROM AUTHOR]