Powering the Future by Iron Sulfide Type Material (FexSy) Based Electrochemical Materials for Water Splitting and Energy Storage Applications: A Review.

Water electrolysis is among the recent alternatives for generating clean fuels (hydrogen). It is an efficient way to produce pure hydrogen at a rapid pace with no unwanted by-products. Effective and cheap water-splitting electrocatalysts with enhanced activity, specificity, and stability are currently widely studied. In this regard, noble metal-free transition metal-based catalysts are of high interest. Iron sulfide (FeS) is one of the essential electrocatalysts for water splitting because of its unique structural and electrochemical features. This article discusses the significance of FeS and its nanocomposites as efficient electrocatalysts for oxygen evolution reaction (OER), hydrogen evolution reaction (HER), oxygen reduction reaction (ORR), and overall water splitting. FeS and its nanocomposites have been studied also for energy storage in the form of electrode materials in supercapacitors and lithium- (LIBs) and sodium-ion batteries (SIBs). The structural and electrochemical characteristics of FeS and its nanocomposites, as well as the synthesis processes, are discussed in this work. This discussion correlates these features with the requirements for electrocatalysts in overall water splitting and its associated reactions. As a result, this study provides a road map for researchers seeking economically viable, environmentally friendly, and efficient electrochemical materials in the fields of green energy production and storage.

Biochar from olive tree twigs and spent malt rootlets as electrodes in Zn-air batteries.

Biochars, i.e. porous carbons obtained by pyrolysis of biomass, can act as electrocatalysts for oxygen evolution and oxygen reduction reaction. In the present work, two biochars have been prepared by using materials of completely different biomass origin: olive-tree twigs and spent malt rootlets (brewery wastes). Both biomass species were subjected to pyrolysis under limited oxygen supply and then they were activated by mixing with KOH and pyrolysis again. The obtained biochars were characterized by several techniques in order to determine their structural characteristics and the composition of their active components. Despite their different origin, the two biochars demonstrated similar structural and compositional characteristics thus highlighting the importance of the pyrolysis and activation procedure. Both biochars were used as electrocatalysts in the operation of rechargeable Zn-air batteries, where they also demonstrated similar electrocatalytic capacities with only a small advantage gained by olive-tree-twigs biochar. Compared to bare nanoparticulate carbon (carbon black), both biochars demonstrated a marked advantage towards oxygen evolution reaction.

Synthesis, Characterization and Performance of Materials for a Sustainable Future.

Today, sustainability represents the key factor for economic progress in compliance with social advancement and environmental protection, driving innovation in materials, processes and technologies [...].

Diffuse reflectance spectroscopy (DRS) and infrared (IR) measurements for studying biofilm formation on common plastic litter polymer (LDPE and PET) surfaces in three different laboratory aquatic environments.

Different species of microorganisms colonize the plastic surfaces and form biofilms depending on the aquatic environment. In the current investigation, characteristics of the plastic surface after exposure to three different aquatic environments based on visualization using scanning electron microscopy (SEM) and spectroscopic (diffuse reflectance (DR) and infrared (IR)) techniques were examined in laboratory bioreactors with time. For both materials, there were no differences observed in the ultraviolet (UV) region among the reactors and several peaks were observed with fluctuating intensities and without any trends. For light density polyethylene (LDPE), peaks indicating the presence of biofilm could be observed in the visible region for activated sludge bioreactor, and for polyethylene terephthalate (PET), freshwater algae biofilm was also visible. PET in freshwater bioreactor is the most densely populated sample both under the optical microscope and SEM. Based on the DR spectra, different visible peaks for LDPE and PET were observed but, in both cases, the visible region peaks (~ 450 and 670 nm) correspond to the peaks found in the water samples of the bioreactors. The difference on these surfaces could not be identified with IR but the fluctuations observed in the UV wavelength region were also detectable using indices obtained from the IR spectra such as keto, ester, and vinyl. For instance, the virgin PET sample shows higher values in all the indices than the virgin LDPE sample [(virgin LDPE: ester Index (I) = 0.051, keto I = 0.039, vinyl I = 0.067), (virgin PET: ester I = 3.5, keto I = 19, vinyl I = 0.18)]. This suggests that virgin PET surface is hydrophilic as expected. At the same time, for all the LDPE samples, all the indices demonstrated higher values (especially for R2) than the virgin LDPE. On the other hand, ester and keto indices for PET samples demonstrated lower values than virgin PET. In addition, DRS technique was able to identify the formation of the biofilm both on wet and dry samples. Both DRS and IR can describe changes in the hydrophobicity during the initial formation of biofilm but DRS can better describe the fluctuations of biofilm in the visible spectra region.

Synthesis, Characterization and Performance of Materials for a Sustainable Future.

The current era has been defined as "The Plastic Era", considering that over the past 50 years the role and importance of polymeric materials in our economy has steadily grown, reaching a production of around a few hundred million tons per year which may even double in the next 20 years [...].

Degradation of 4-Tert-Butylphenol in Water Using Mono-Doped (M1: Mo, W) and Co-Doped (M2-M1: Cu, Co, Zn) Titania Catalysts.

Mono-doped (Mo-TiO2 and W-TiO2) and co-doped TiO2 (Co-Mo-TiO2, Co-W-TiO2, Cu-Mo-TiO2, Cu-W-TiO2, Zn-Mo-TiO2, and Zn-W-TiO2) catalysts were synthesized by simple impregnation methods and tested for the photocatalytic degradation of 4-tert-butylphenol in water under UV (365 nm) light irradiation. The catalysts were characterized with various analytical methods. X-ray diffraction (XRD), Raman, Diffuse reflectance (DR) spectroscopies, Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), and Energy dispersive spectroscopy (EDS) were applied to investigate the structure, optical properties, morphology, and elemental composition of the prepared catalysts. The XRD patterns revealed the presence of peaks corresponding to the WO3 in W-TiO2, Co-W-TiO2, Cu-W-TiO2, and Zn-W-TiO2. The co-doping of Cu and Mo to the TiO2 lattice was evidenced by the shift of XRD planes towards higher 2θ values, confirming the lattice distortion. Elemental mapping images confirmed the successful impregnation and uniform distribution of metal particles on the TiO2 surface. Compared to undoped TiO2, Mo-TiO2 and W-TiO2 exhibited a lower energy gap. Further incorporation of Mo-TiO2 with Co or Cu introduced slight changes in energy gap and light absorption characteristics, particularly visible light absorption. In addition, photoluminescence (PL) showed that Cu-Mo-TiO2 has a weaker PL intensity than undoped TiO2. Thus, Cu-Mo-TiO2 showed better catalytic activity than pure TiO2, achieving complete degradation of 4-tert-butylphenol under UV light irradiation after 60 min. The application of Cu-Mo-TiO2 under solar light conditions was also tested, and 70% of 4-tert-butylphenol degradation was achieved within 150 min.

Tuning the Physicochemical Properties of Nanostructured Materials through Advanced Preparation Methods.

Over the last few decades, nanotechnology has received a huge level of interest due to its extensive applications in various fields, including catalysis, electronics, optics, energy, and the environment [...].

The interplay between acid-base properties and Fermi level pinning of a nano dispersed tungsten oxide - titania catalytic system.

A series of WO3/TiO2 catalysts were synthesized, characterized, and evaluated for the NO selective catalytic reduction (SCR) with NH3. Based on a wide range of characterization techniques, a detailed model was developed that describes the interfacial electron transfer between WO3 and TiO2 and defines a relationship between the acid-base properties of the catalytic surface and electronic structure modification. The electronic interactions at the WO3/TiO2 interface were quantified using variations in the system's electronic structure. Altering the dispersion and size of the WO3 nanostructures results to drastic changes in titania's surface electron distribution, which are reflected in the pinning of Fermi level through an electron transfer process between WO3 and TiO2. The variations in the Fermi level were further related to changes in the point of zero charge (PZC) values and the activity towards NO SCR with NH3, which was used as a test reaction. Temperature Programmed Surface Reaction (TPSR) was employed to study the catalytic activity at temperatures ranging from 30 °C to 500 °C and was quantitatively correlated to changes in coverage and interfacial charge transfer. We demonstrate that higher WO3 loading on TiO2 results in a stronger electronic interaction and a higher catalytic activity. This is because electron transfer increases the surface electron density, which enhances the surface basicity of TiO2. The concomitant decrease in the adsorption energy of NH3 results in a decrease in the activation energy, which is reflected in the SCR temperature onset.

Hybrid Biochar/Ceria Nanomaterials: Synthesis, Characterization and Activity Assessment for the Persulfate-Induced Degradation of Antibiotic Sulfamethoxazole.

Biochar from spent malt rootlets was employed as the template to synthesize hybrid biochar-ceria materials through a wet impregnation method. The materials were tested for the activation of persulfate (SPS) and subsequent degradation of sulfamethoxazole (SMX), a representative antibiotic, in various matrices. Different calcination temperatures in the range 300-500 °C were employed and the resulting materials were characterized by means of N2 adsorption and potentiometric mass titration as well as TGA, XRD, SEM, FTIR, DRS, and Raman spectroscopy. Calcination temperature affects the biochar content and the physicochemical properties of the hybrid materials, which were tested for the degradation of 500 µg L-1 SMX with SPS (in the range 200-500 mg L-1) in various matrices including ultrapure water (UPW), bottled water, wastewater, and UPW spiked with bicarbonate, chloride, or humic acid. Materials calcined at 300-350 °C, with a surface area of ca. 120 m2 g-1, were the most active, yielding ca. 65% SMX degradation after 120 min of reaction in UPW; materials calcined at higher temperatures as well as bare biochar were less active. Degradation decreased with increasing matrix complexity due to the interactions amongst the surface, the contaminant, and the oxidant. Experiments in the presence of scavengers (i.e., methanol, t-butanol, and sodium azide) revealed that sulfate and hydroxyl radicals as well as singlet oxygen were the main oxidative species.

Study of the Functionalities of a Biochar Electrode Combined with a Photoelectrochemical Cell.

Biochar has been obtained by pyrolysis of spent malt rootlets under limited oxygen supply and further activated by mixing with KOH and pyrolyzed again at high temperature. The total specific surface area of such activated biochar was 1148 m2 g-1, while that of micropores was 690 m2 g-1. This biochar was used to make a functional electrode by deposition on carbon cloth and was combined with a photoelectrochemical cell. The biochar electrode functioned as a supercapacitor in combination with the electrolyte of the cell, reaching a specific capacity of 98 Fg-1, and it was capable of storing charges generated by the cell, proving current flow both under illumination and in the dark. The same electrode could be used as an air-cathode providing oxygen reduction functionality and thus demonstrating interesting electrocatalyst properties.

Valorisation of agricultural waste derived biochars in aquaculture to remove organic micropollutants from water - experimental study and molecular dynamics simulations.

In this work, we evaluated the valorisation of agricultural waste materials by transforming coconut husks and shells, corncobs and rice straw into biochar for water treatment in aquaculture. We compared the biochars' suitability for removal of organic micropollutants (acetaminophen, oxytetracycline, tetracycline, enrofloxacin, atrazine, diuron and diclofenac) from surface water needed for aquaculture. The biochars were prepared by three methods ranging from inexpensive drum kilns (200 °C) to pyrolysis with biogasfication (350-750 °C). Overall, antibiotics tetracycline and enrofloxacin were the most strongly sorbed micropollutants, and coconut husk biochar prepared at 750 °C was the best sorbent material. Molecular Dynamics simulations indicated that the major sorption mechanism is via π-π stacking interactions and there is a possibility of multilayer sorption for some of the micropollutants. We observed, a strong impact of ionic strength (salinity), which is an important consideration in coastal aquaculture applications. High salinity decreased the sorption for antibiotics oxytetracycline, tetracycline and enrofloxacin but increased diclofenac, atrazine and diuron sorption. We considered coconut husk biochar produced in drum kilns the most practical option for biochar applications in small-scale coastal aquacultures in South Asia. Pilot trials of canal water filtration at an aquaculture farm revealed that micropollutant sorption by coconut husk biochar under real-world conditions might be 10-500 times less than observed in the laboratory studies. Even so, biochar amendment of sand enhanced the micropollutant retention, which may facilitate subsequent biodegradation and improve the quality of brackish surface water used for food production in coastal aquaculture.

Degradation of sulfamethoxazole with persulfate using spent coffee grounds biochar as activator.

In the present study, biochar from spent coffee grounds was synthesized via pyrolysis at 850 °C for 1 h, characterized and employed as catalyst for the degradation of sulfamethoxazole (SMX) by persulfate activation. A variety of techniques, such as physisorption of N2, scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis, and potentiometric mass titration, were employed for biochar characterization. The biochar has a surface area of 492 m2/g, its point of zero charge is 6.9, while mineral deposits are limited. SMX degradation experiments were performed mainly in ultrapure water (UPW) at persulfate concentrations between 100 and 1000 mg/L, biochar concentrations between 50 and 200 mg/L, SMX concentrations between 500 and 2000 µg/L and initial solution pH between 3 and 10. Real matrices, besides UPW, were also tested, namely bottled water (BW) and treated wastewater (WW), while synthetic solutions were prepared spiking UPW with bicarbonate, chloride, humic acid or alcohols. Almost complete removal of SMX can be achieved using 200 mg/L biochar and 1000 mg/L sodium persulfate (SPS) within 75 min. The presence of biochar is important for the degradation process, while the activity of the biochar increases linearly with SPS concentration. Degradation follows a pseudo-order kinetic model and the rate increases with increasing biochar concentration and decreasing SMX concentration. Although SMX adsorption onto the biochar surface is favored at acidic conditions, degradation proceeds equally fast regardless of the initial solution pH. Reactions in either real matrix are slower, resulting in 55% SMX removal in 60 min for WW. Bicarbonate causes severe inhibition as only 45% of SMX can be removed within 75 min in UPW. The addition of alcohol slightly inhibits degradation suggesting that the reaction pathway is either under electron transfer control or due to the generation of surface oxygen radicals with higher oxidation potential than the homogeneously produced radicals.

Degradation of methylparaben by sonocatalysis using a Co-Fe magnetic carbon xerogel.

The degradation of methylparaben (MP) through 20 kHz ultrasound coupled with a bimetallic Co-Fe carbon xerogel (CX/CoFe) was investigated in this work. Experiments were performed at actual power densities of 25 and 52 W/L, catalyst loadings of 12.5 and 25 mg/L, MP concentrations between 1 and 4.2 mg/L and initial pH values between 3 and 10 in ultrapure water (UPW). Matrix effects were studied in bottled water (BW) and secondary treated wastewater (WW), as well as in UPW spiked with bicarbonate, chloride or humic acid. The pseudo-first order kinetics of MP degradation increase with power and catalyst loading and decrease with MP concentration and matrix complexity; moreover, the reaction is also favored at near-neutral conditions and in the presence of dissolved oxygen. The contribution of the catalyst is synergistic to the sonochemical degradation of MP and the extent of synergy is quantified to be >45%. This effect was ascribed to the ability of CX/CoFe to catalyze the dissociation of hydrogen peroxide, formed through water sonolysis, to hydroxyl radicals. Experiments in UPW spiked with an excess of tert-butanol (radical scavenger), sodium dodecyl sulfate or sodium acetate (surfactants) led to substantially decreased rates (i.e. by about 8 times), thus implying that the liquid bulk and the gas-liquid interface are major reaction sites. The stability of CX/CoFe was shown by performing reusability cycles employing magnetic separation of the catalyst after the treatment stage. It was found that the CX/CoFe catalyst can be reused in up to four successive cycles without noteworthy variation of the overall performance of the sonocatalytic process.

Using diffuse reflectance spectroscopy (DRS) technique for studying biofilm formation on LDPE and PET surfaces: laboratory and field experiments.

Biofilm formation on plastic debris needs to be further investigated, because microorganisms attached to plastics are transferred in all three dimensions to new regions by ocean currents. The current study aims to investigate biofilm formation on plastic strips in aquatic ecosystems using a simple physicochemical method commonly used to characterize solid surfaces, namely, the diffuse reflectance UV-Vis spectroscopy (DRS) method. Using virgin polymers that have not being exposed to the environment as a reference, DRS peaks can be attributed to the microorganisms attached to the polymer surface with time. The polymers tested were low-density polyethylene (LDPE) and polyethylene terephthalate (PET). For LDPE strips for all sampling times in the field, the development of the peaks among 10 similar samples was rather uniform in terms of peak wavelength with time. For PET strips during the early sampling time, the development of the peaks among 10 similar samples was rather uniform in terms of peak wavelength but varied in terms of intensity. This last observation phased out with longer exposure times that the peaks had similar distribution in terms of peak wavelength and intensity. Similar experiments were run for longer exposure times both in an oligotrophic laboratory bioreactor and in the marine environment. In both cases, the biofilm on PET samples seems to reach a steady state faster than LDPE with similar peaks found on both samples DRS proved to be a robust and useful tool to study the formation of biofilm on plastic samples without any pretreatment and without sample destruction. Graphical abstract.

The influence of the preparation method and the Co loading on the structure and activity of cobalt oxide/gamma-alumina catalysts for NO reduction by propene.

In the present work we studied the influence of the preparation method and the Co loading on the physicochemical properties and the catalytic activity of the cobalt oxide/gamma-alumina catalysts for the reduction of NO by propene under net oxidizing conditions. Two series of catalysts containing 1 and 5% w/w Co, respectively, were prepared using three preparation methods, namely, the equilibrium deposition filtration (EDF), the conventional incipient wetness impregnation (IWI) and the IWI adding nitrilotriacetic acid (nta) in the impregnating solution (IWInta). The catalysts were tested at various temperatures in the range 300-550 degrees C using a fixed-bed microreactor for the NO reduction by propene under lean burn conditions. The evolution of the Co species on the alumina surface was followed after each preparation step by diffuse reflectance spectroscopy (DRS). It was found that the catalysts of the first series were more active for the title reaction than those of the second one. The EDF sample of the first series was proved to be the most active and selective one followed by the IWI and then the IWInta sample of the same series. The DRS results indicated that the enhanced activity and selectivity of the EDF sample could be attributed to the increased concentration of isolated Co(II) inner sphere complexes of octahedral coordination, which are formed on the support surface by adsorption of the corresponding aqueous complexes, [Co(H2O)6]2+, being in the impregnating solution. These inner sphere complexes are transformed upon thermal treatment into a CoAl2O4 like phase with high dispersion. On the other hand, the [Co(H2O)6]2+(NO3)2- and [Co-nta]-.NH4+(or H+) and/or [Co-2nta]4+.4NH4+(or 4H+) complex salts, precipitated on the alumina surface upon drying in the cases of the IWI and IWInta samples, are transformed upon calcination into CoAl2O4 like phases with lower dispersion. All the samples of the second series promoted the propene combustion as well as the oxidation of NO and N2, used as carrier gas, to NO2. DRS results revealed that in all these samples cobalt(III) oxo species are formed in addition to the CoAl2O4 phase. These species are considered to be responsible for the enhancement of the rates of the oxidation reactions mentioned above.

Kinetics of adsorption of the cobalt ions on the "electrolytic solution/gamma-alumina" interface.

In the present work we studied, for the first time, the kinetics of adsorption of the Co(H(2)O)(6)(2+) species on the "electrolytic solution/gamma-Al(2)O(3)" interface at pH = 7 and 25 degrees C for a very broad range of Co(II) surface concentrations ranged from 0.03 to 6 theoretical Co(H(2)O)(6)(2+) surface layers. Moreover, we studied the surface dissolution of gamma-alumina in the presence of the Co(H(2)O)(6)(2+) ions in the impregnating solution, the contribution of the Co(II) desorption on the whole deposition process and the deposition isotherm. It was found that under the conditions where the deposition has taken place, the dissolution of the gamma-alumina surface is negligible even in the presence of the Co(H(2)O)(6)(2+) species in the impregnating solution. It was, moreover, inferred that the Co(II) desorption does not participate significantly to the whole deposition process. It was found that the deposition kinetics may be described by the following kinetic expression r(Co,bulk) = k'C(Co,bulk)(2), which relates the rate of disappearance of the Co(H(2)O)(6)(2+) ions from the impregnating solution, r(Co,bulk,) with their concentration C(Co,bulk). This kinetic expression may be derived assuming the following deposition scheme: nS + 2[Co(H(2)O)(6)(2+)] --> S(n) - [Co(H(2)O)(x,x)(<)(6)(2+)](2), where S represents the surface reception sites. The above expressions indicated that two Co(H(2)O)(6)(2+) ions are involved, from the side of the interface, in the reaction with the reception sites. It seems probable that the deposition step involves the simultaneous adsorption and dimerization of the two interfacial Co(H(2)O)(6)(2+) ions through (hydr)oxobridges. On the other hand, the sigmoidal form of the deposition isotherm and the dependence of the apparent rate constant, k', on the interfacial Co(II) concentration suggested that the already deposited Co(II) species may be involved in the reception sites, S, promoting the adsorption and resulting to the formation of multinuclear complexes and Co(II) surface precipitates. Finally, reasonable interface potential values for oxides were determined for the first time using kinetic results.

Adsorption of cobalt ions on the "electrolytic solution/gamma-alumina" interface studied by diffuse reflectance spectroscopy (DRS).

Diffuse reflectance spectroscopy was used for the first time to investigate the adsorption of the [Co(H2O)6]2+ ions on the interface developed between the surface of the gamma-alumina particles and the electrolytic aqueous solutions used for the preparation of cobalt-supported gamma-alumina catalysts by equilibrium deposition filtration. The formation of inner-sphere Co(II) surface complexes in which Co(II) is in octahedral symmetry was confirmed. A deconvolution peak centered at approximately 585 nm was attributed to the exchange of one aqua ligand with one AlxOHy (x = 1, 2, or 3; y = 0 or 1) negatively charged surface group resulting in the formation of mononuclear monosubstituted inner-sphere Co(II) complexes at a Co(II) surface concentration equal to 0.02 micromol of Co(II)/m2. It was inferred that as the surface Co(II) concentration increases the formation of disubstituted and/or trisubstituted surface complexes is favored with respect to the formation of monosubstituted Co(II) surface complexes. A deconvolution peak centered at approximately 640 nm was attributed to the exchange of one or more aqua ligands with bridging hydroxo ligands (Co-O-H). The relative magnitude of this peak increases with the Co(II) surface concentration, reflecting the increasing formation of binuclear, oligonuclear, and multinuclear Co(II) surface complexes and then the formation of the Co(II) surface precipitate.

Adsorption of cobalt species on the interface, which is developed between aqueous solution and metal oxides used for the preparation of supported catalysts: a critical review.

In the present review article, we present the efforts done so far for elucidating the mechanism of adsorption of the Co(II) species, mainly Co(H(2)O)(6)(2+), on the interfacial region developed between metal oxide particles, used as catalytic supports, and aqueous electrolytic solutions. Specifically, we present: (i) the principal modes of deposition of the transition metal ionic species (TMIS) on the surface of oxidic supports related with the various methodologies used for the preparation of the supported catalysts; (ii) the state of the art concerning the general aspects of the adsorption mechanisms of the TMIS on the aforementioned interfacial region; and (iii) the works reported so far dealing with the adsorption of the Co(II) species on the surface of gamma-Al(2)O(3) (gamma-alumina), alpha-Al(2)O(3) (alpha-alumina), TiO(2) (rutile), and SiO(2) (silica). It was concluded that the mechanism of adsorption depends on two main factors: on the Co(II) surface concentration and on the nature of the support surface. It seems that, generally, the mechanism changes progressively along the Co(II) surface concentration from the deposition of monodentate-mononuclear inner sphere complexes, weakly evidenced in too low values of the Co(II) surface concentration, to multidentate, multinuclear inner sphere surface complexes at relatively low Co(II) surface concentrations, and then into surface Co(OH)(2)-like, eventually mixed precipitates, at relatively high Co(II) surface concentrations but at pH values lower than those required for bulk precipitation. In all cases, Co(II) forms surface species with Co(II) in octahedral symmetry. However, the exact Co(II) surface concentration values, in which the abovementioned two transitions (concerning the deposited phase) take place, depends on the kind of the support. Thus, SiO(2) favors the formation of the Co(OH)(2)-like precipitates even at relatively low Co(II) surface concentrations. In contrast, TiO(2) favors the formation of mononuclear or oligonuclear surface complexes. Finally, alumina, which exhibits the maximum adsorption capacity, favors the formation of highly defected Co(OH)(2)-like precipitates, probably mixed Co-Al precipitates. The exact local structure of the inner sphere Co(II) surface complexes, formed by exchanging the H(2)O ligands with surface oxygens, has been already approached but only for the surface planes of the alpha-Al(2)O(3) and rutile monocrystals. This structure remains up to now rather unclear for the polycrystalline oxides used as catalytic supports.

Potentiometric mass titrations: a quick scan for determining the point of zero charge.

A novel technique for determining the point of zero charge (pzc), called 'potentiometric mass titrations technique', has been developed and used for determining the pzc of several industrially used catalytic supports (SiO2, TiO2, gamma-Al2O3 and MgO).