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The effects of pH on nutrient availability are not solely caused by to the effects on reaction with soils but are an interaction between these effects and the effects on rate of uptake by plants. Some effects are specific to particular ions, but an important aspect is that plant roots and soil particles both have variable charge surfaces. This influences availability, but in opposite directions. Sulfate is an example of this interplay. Its sorption by soil decreases markedly with increasing pH and thus “soil availability” increases. However, plant uptake also decreases with increasing pH thus “plant availability” decreases. For phosphate, the plant effect is stronger than the soil effect and uptake decreases with increasing pH. In contrast, effects of increasing pH on molybdate adsorption are so large that they dominate the overall effect. Sorption of cations, such as zinc or copper, increases with increasing pH but uptake rate also increases. The net effect is a small decrease in availability with increasing pH. Boron is an exception; there are small effects of pH on sorption; and it is the uncharged boric acid molecules that are taken up by plant roots. Their uptake is not affected by charge and uptake is proportional to the concentration of uncharged boric acid molecules. We argue that emphasis on the effects of pH on reactions with soil has led to a distorted picture of the effects of pH on nutrient availability.

Despite pioneering as the holy grail in photocatalysts, abundant reports have demonstrated that g-C 3 N 4 performs poor photocatalytic activity due to its high recombination rate of photo-induced charge carriers. Many efforts have been conducted to overcome this limitation in which the semiconductor–semiconductor coupling strategies toward heterojunction formation were considered as the easiest but the most effective method. Herein, a one-pot solid-state reaction of thiourea and sodium molybdate as precursors at different temperatures under N 2 gas was applied for preparing composites of MoS 2 /g-C 3 N 4 . The physicochemical characterization of the final products determines the variation in contents of components (MoS 2 and g-C 3 N 4 ) via the increase of synthesis temperature. The enhanced photocatalytic activity of the MoS 2 /g-C 3 N 4 composites was evaluated by the degradation of Rhodamine B in an aqueous solution under visible light. Therein, composites synthesized at 500 °C showed the best photocatalytic performance with a degradation efficiency of 90%, much higher than that of single g-C 3 N 4 . The significant improvement in photocatalytic performance is attributed to the enhancement in light-harvesting and extension in photo-induced charge carriers’ lifetime of composites which are originated from the synergic effect between the components. Besides, the photocatalytic mechanism is demonstrated to well-fit into the S-scheme pathway with apparent evidences.

Molybdenum, as a component of the iron-molybdenum cofactor of nitrogenase, is essential for symbiotic nitrogen fixation. This nutrient has to be provided by the host plant through molybdate transporters. Members of the molybdate transporter family Molybdate Transporter type 1 (MOT1) were identified in the model legume Medicago truncatula and their expression in nodules was determined. Yeast toxicity assays, confocal microscopy, and phenotypical characterization of a Transposable Element from Nicotiana tabacum (Tnt1) insertional mutant line were carried out in the one M. truncatula MOT1 family member specifically expressed in nodules. Among the five MOT1 members present in the M. truncatula genome, MtMOT1.3 is the only one uniquely expressed in nodules. MtMOT1.3 shows molybdate transport capabilities when expressed in yeast. Immunolocalization studies revealed that MtMOT1.3 is located in the plasma membrane of nodule cells. A mot1.3-1 knockout mutant showed impaired growth concomitant with a reduction of nitrogenase activity. This phenotype was rescued by increasing molybdate concentrations in the nutritive solution, or upon addition of an assimilable nitrogen source. Furthermore, mot1.3-1 plants transformed with a functional copy of MtMOT1.3 showed a wild-type-like phenotype. These data are consistent with a model in which MtMOT1.3 is responsible for introducing molybdate into nodule cells, which is later used to synthesize functional nitrogenase.

MoO 4 2− -H 2 O 2 is an efficient oxidation system for the conversion of para -alkyl-phenols to high value-added para -peroxyquinols and para -quinols, but its large-scale application is still limited to difficulty in catalyst recovery. This paper discloses that a hydrated calcium silicate (CS)-supported calcium molybdate (CM) catalyst (CMS) is easily fabricated in high-yield and large-scale by simple coprecipitation. Compared to the unsupported CM and Na 2 MoO 4 , CMS has an enhanced catalytic activity for the selective oxidation of para -alkyl-phenols, but also it shows a drastically improved selectivity for the target products, which can achieve 84% conversion and 100% selectivity for the goal products in catalyzing the oxidation of 2,4-xylenol with H 2 O 2 in water. Also, it is very efficient for the selective oxidation of other p -alkyl substituted phenols in water or methanol, especially including the highly selective oxidation of p -cresol which is easy to be overoxidized. More importantly, the CMS catalytic system can be conveniently recovered and repeatedly run without significant activity loss, showing a good reusability. In situ UV-DRS and FT-IR spectra, as well as H 2 O 2 decomposition experiments support that the alkaline CS carrier can induce the reaction of CMS with H 2 O 2 to preferentially generate the mono-/di-peroxomolybdates as the key species for the selective oxidation of para -alkyl-phenols. Graphical Abstract

Electrocatalytic conversion of organic small molecules is a promising technique for value-added chemical productions but suffers from high precious metal consumption, poor stability of electrocatalysts and tedious product separation. Here, a Pd/NiMoO 4 /NF electrocatalyst with much lowered Pd loading amount (3.5 wt.%) has been developed for efficient, economic, and ultra-stable glycolate synthesis, which shows high Faradaic efficiency (98.9%), yield (98.8%), and ultrahigh stability (1500 h) towards electrocatalytic ethylene glycol oxidation. Moreover, the obtained glycolic acid has been converted to value-added sodium glycolate by in-situ acid-base reaction in the NaOH electrolyte, which is atomic efficient and needs no additional acid addition for product separation. Moreover, the weak adsorption of sodium glycolate on the catalyst surface plays a significant role in avoiding excessive oxidation and achieving high selectivity. This work may provide instructions for the electrocatalyst design as well as product separation for the electrocatalytic conversions of alcohols. Here, the authors report a path for electrocatalytic conversions of alcohols through in-situ acid-base reaction and the design of electrocatalysts. In this work, the electrocatalyst had reduced Pd content, improved efficiency, and lowered costs.

Simultaneously activating metal and lattice oxygen sites to construct a compatible multi-mechanism catalysis is expected for the oxygen evolution reaction (OER) by providing highly available active sites and mediate catalytic activity/stability, but significant challenges remain. Herein, Fe and S dually modulated NiFe oxyhydroxide (R-NiFeOOH@SO 4 ) is conceived by complete reconstruction of NiMoO 4 ·xH 2 O@Fe,S during OER, and achieves compatible adsorbate evolution mechanism and lattice oxygen oxidation mechanism with simultaneously optimized metal/oxygen sites, as substantiated by in situ spectroscopy/mass spectrometry and chemical probe. Further theoretical analyses reveal that Fe promotes the OER kinetics under adsorbate evolution mechanism, while S excites the lattice oxygen activity under lattice oxygen oxidation mechanism, featuring upshifted O 2 p band centers, enlarged d-d Coulomb interaction, weakened metal-oxygen bond and optimized intermediate adsorption free energy. Benefiting from the compatible multi-mechanism, R-NiFeOOH@SO 4 only requires overpotentials of 251 ± 5/291 ± 1 mV to drive current densities of 100/500 mA cm −2 in alkaline media, with robust stability for over 300 h. This work provides insights in understanding the OER mechanism to better design high-performance OER catalysts. The oxygen evolution reaction is crucial for energy conversion but faces challenges in catalyst optimization. Here, the authors present a dual-modulated NiFe oxyhydroxide (R-NiFeOOH@SO4) that enhances OER performance through optimized metal and lattice oxygen sites, achieving a compatible multi-mechanism.

Molybdate inhibits sulfate respiration in sulfate-reducing bacteria (SRB). It is used as an inhibitor to indirectly evaluate the role of SRB in mercury methylation in the environment. Here, the SRB Pseudodesulfovibrio hydrargyri BerOc1 was used to assess the effect of molybdate on cell growth and mercury methylation under various metabolic conditions. Geobacter sulfurreducens PCA was used as the non-SRB counterpart strain with the ability to methylate mercury. While PCA growth and methylation are not affected by molybdate, 1 mM of molybdate inhibits BerOc1 growth under sulfate respiration (50% inhibition) but also under fumarate respiration (complete inhibition). Even more surprising, mercury methylation of BerOc1 is totally inhibited at 0.1 mM of molybdate when grown under sulfate or fumarate respiration with pyruvate as the electron donor. As molybdate is expected to reduce cellular ATP level, the lower Hg methylation observed with pyruvate could be the consequence of lower energy production. Although molybdate alters the expression of hgcA (mercury methylation marker) and sat (involved in sulfate reduction and molybdate sensitivity) in a metabolism-dependent manner, no relationship with mercury methylation rates could be found. Our results show, for the first time, a specific mercury methylation inhibition by molybdate in SRB.

Non-noble transition metal oxides are abundant in nature. However, they are widely regarded as catalytically inert for hydrogen evolution reaction (HER) due to their scarce active electronic states near the Fermi-level. How to largely improve the HER activity of these kinds of materials remains a great challenge. Herein, as a proof-of-concept, we design a non-solvent strategy to achieve phosphate substitution and the subsequent crystal phase stabilization of metastable β-NiMoO 4 . Phosphate substitution is proved to be imperative for the stabilization and activation of β-NiMoO 4 , which can efficiently generate the active electronic states and promote the intrinsic HER activity. As a result, phosphate substituted β-NiMoO 4 exhibits the optimal hydrogen adsorption free energy (−0.046 eV) and ultralow overpotential of −23 mV at 10 mA cm −2 in 1 M KOH for HER. Especially, it maintains long-term stability for 200 h at the large current density of 1000 mA cm −2 with an overpotential of only −210 mV. This work provides a route for activating transition metal oxides for HER by stabilizing the metastable phase with abundant active electronic states. Non-noble transition metal oxides are common yet typically poor hydrogen evolution catalysts due to scarce active electronic states. This work provides a route for achieving hydrogen evolution at high current densities by stabilizing a metastable NiMoO 4 phase with abundant active electronic states.

Copper (Cu) is an essential trace element, but excessive Cu intake can induce poor performance and Cu poisoning and result in various health problems. Cu and molybdenum (Mo) antagonize each other in vivo. Therefore, Mo can reduce the absorption and utilization of Cu. The aims of this study were to investigate the impacts of Mo fertilization on antioxidant capacity of grazing Nanjiang brown goat on Cu-polluted meadow and explore the control methods of Cu pollution in natural pasture. Fertilization and grazing experiments were carried out in Liangshan Yi Nationality Prefecture of the Western Sichuan Plateau, Sichuan Province, Southwest China. Cu-polluted meadows of 12 hm2 were fenced, and randomly divided into two groups (3 replications/group, 2 hm2/replication), control group and treatment group, fed with basic diets supplemented with 0 and 3 kg Mo/hm2 [ammonium molybdate tetrahydrate, (NH4)6Mo7O24·4H2O], respectively. In the current study, 36 healthy Nanjiang brown goats (1 year old, 32.8 ± 1.1 kg) were randomly divided into two groups (3 replications/group, 6 goats/replication) and assigned to the experimental pastures. The grazing experiment lasted for 60 days. The results showed that the concentration of Mo in soil in treatment group was 96.28 mg/kg, far exceeding the normal levels. At days 30 and 60, the levels of Hb, RBC, and PCV in blood in treatment group and the activities of serum SOD, GSH-Px, T-AOC, CAT, and Cp were higher than those in control group (P < 0.01). The MDA content in treatment group was lower than that in control group (P < 0.01). The contents of Cu in blood and liver in treatment goats were lower than those in control animals (P < 0.01). The contents of Zn and Mo in blood and liver in treatment goats were higher than those in control animals (P < 0.01). The Mn content in liver in treatment group was higher than that in control animals (P < 0.01). These results indicated that fertilization of (NH4)6Mo7O24 not only markedly influenced the mineral contents in blood and liver, but also extremely improved antioxidant capacity of grazing Nanjiang brown goat from fertilized pastures and relieved the damage caused by Cu pollution.

A Molybdate intercalated copper–aluminium hydrotalcite (CAM) material was synthesised using a simple co-precipitation technique, employing varying amounts of molybdate anions. Powder XRD, FT-IR, and TEM studies revealed the presence of molybdate species in the interlayer spaces and the formation of layered hydrotalcite structures. The resultant CAM materials have been explored for the hydrogenation of 5-hydroxymethyl furan using water as a green solvent in liquid-phase conditions under a hydrogen atmosphere. The catalyst showed around 60% conversion with the selective formation of 2,5-bishydroxymethyl furan (BHMF). The activity remains intact for five cycles. The increase in reaction temperature enhanced the conversion level to 80%, with the cost of a decrease in the selectivity of BHMF to 74%. The uniform dispersion of copper-molybdenum and strong interaction in the presence of a hydrogen atmosphere favoured better activity.