The post-harvest fumigant, sulfuryl fluoride (SO2F2), is a >1000-fold more potent greenhouse gas than carbon dioxide and methane. Pilot studies have shown that SO2F2 fumes vented from fumigation chambers can be captured and hydrolyzed by hydroxide (OH-) and hydrogen peroxide (H2O2) at pH ∼ 12 in a scrubber, producing SO42- and F- as waste salts. To reduce the costs and challenges associated with purchasing and mixing these reagents onsite, this study evaluates the electrochemical generation of OH- and H2O2 within spent scrubbing solution, taking advantage of the waste SO42- and F- as free sources of electrolyte. The study used a gas diffusion electrode constructed from carbon paper coated with carbon black as a catalyst selective for the reduction of O2 to H2O2. Under galvanostatic conditions, the study evaluated the effect of electrochemical conditions, including applied cathodic current density and electrolyte strength. Within an electrolyte containing 200 mM SO42- and 400 mM F-, comparable to the waste salts generated by a SO2F2 scrubbing event, the system produced 250 mM H2O2 at pH 12.6 within 4 h with a Faradaic efficiency of 98.8% for O2 reduction to H2O2. In a scrubbing-water sample from lab-scale fumigation, the system generated ∼200 mM H2O2 at pH 13.5 within 4 h with a Faradaic efficiency of 75.6%. A comparison of the costs to purchase NaOH and H2O2 against the electricity costs for electrochemical treatment indicated that the electrochemical approach could be 38-71% lower, depending on the local cost of electricity.

The hydroxide exchange membrane fuel cells (HEMFCs) are promising but lack of high-performance anode hydrogen oxidation reaction (HOR) electrocatalysts. The platinum group metals (PGMs) have the HOR activity in alkaline medium two to three orders of magnitude lower than those in acid, leading to the high required PGMs amount on anode to achieve high HEMFC performance. The mechanism study demonstrates the hydrogen binding energy of the catalyst determines the alkaline HOR kinetics, and the adsorbed OH and water on the catalyst surface promotes HOR. Iridium (Ir) has a unique advantage for alkaline HOR due to its similar hydrogen binding energy to Pt and enhanced adsorption of OH. However, the HOR activity of Ir/C is still unsatisfied in practical HEMFC applications. Further fine tuning the adsorption of the intermediate on Ir-based catalysts is of great significance to improve their alkaline HOR activity, which can be reasonably realized by structure design and composition regulation. In this concept, we address the current understanding about the alkaline HOR mechanism and summarize recent advances of Ir-based electrocatalysts with enhanced alkaline HOR activity. We also discuss the perspectives and challenges on Ir-based electrocatalysts in the future.

Di-μ-hydroxido-bis-[di-bromido-(di-methyl-formamide-κO)ethyl-tin(IV)], [Sn2Br4(C2H5)2(OH)2(C3H7NO)2], was prepared from ethyl-tin(IV) bromide and N,N-di-methyl-formamide (DMF) in air. The crystal structure exhibits the typical structural features of dimeric Lewis-base-stabilized monoorganotin(IV)-dihalide-hydroxides, RSnHal2(OH), i.e. two octa-hedrally coordinated Sn atoms are linked together via two bridging hydroxide groups, resulting in a centrosymmetric four-membered rhomboid-like Sn-OH ring with acute angles at the Sn atom, obtuse angles at the O atoms and two different tin-oxygen bond lengths. With the shorter bond trans to the ethyl group, this observation underlines once more the so-called trans-strengthening effect in monoorganotin(IV) com-pounds with octa-hedrally coordinated Sn atoms. Differences and similarities in the bond lengths and angles in the four-membered Sn-OH rings have been worked out for the rings in dimeric diorganotin(IV)-halide-hydroxides, [R 2SnHal(OH)]2, and hydrates of dimeric tin(IV)-trihalide-hydroxide-aqua-hydrates, [SnHal3(OH)(H2O)]2·nH2O.

Advanced photocatalysts are highly desired to activate the photocatalytic CO2reduction reaction (CO2RR) with low concentration. Herein, the NiSn(OH)6with rich surface lattice hydroxyls was synthesized to boost the activity directly under the natural air. Results showed that terminal Ni-OH could serve as donors to feed protons and generate oxygen vacancies (VO), thus beneficial to convert the activated CO2(HCO3-) mainly into CO (5.60μmol g-1) in the atmosphere. It was flexible and widely applicable for a stable CO2RR from high pure to air level free of additionally adding H2O reactant, and higher than the traditional gas-liquid-solid (1.58μmol g-1) and gas-solid (4.07μmol g-1) reaction system both using high pure CO2and plenty of H2O. The strong hydrophilia by the rich surface hydroxyls allowed robust H2O molecule adsorption and dissociation at VOsites to achieve the Ni-OH regeneration, leading to a stable CO yield (11.61μmol g-1) with the enriched renewable VOregardless of the poor CO2and H2O in air. This work opens up new possibilities for the practical application of natural photosynthesis.

Hydroxides are the archetype of layered crystals with metal-oxygen (M-O) octahedron units, which have been widely investigated as oxygen evolution reaction (OER) catalysts. However, the better crystallinity of hydroxide materials, the more perfect octahedral symmetry and atomic ordering, resulting in the less exposed metal sites and limited electrocatalytic activity. Herein, a glassy state hydroxide material featuring with short-range order and long-range disorder structure is developed to achieve high intrinsic activity for OER. Specifically, a rapid freezing point precipitation method is utilized to fabricate amorphous multi-component hydroxide. Owing to the freezing-point crystallization environment and chaotic M-O (M = Ni/Fe/Co/Mn/Cr etc.) structures, the as-fabricated NiFeCoMnCr hydroxide exhibit a highly-disordered glassy structure, as-confirmed by X-ray/electron diffraction, enthalpic response, and pair distribution function analysis. The as-achieved glassy-state hydroxide materials display a low OER overpotential of 269 mV at 20 mA cm-2 with a small Tafel slope of 33.3 mV dec-1 , outperform the benchmark noble-metal RuO2 catalyst (341 mV, 84.9 mV dec-1 ) . Operando Raman and density functional theory studies reveal that the glassy state hydroxide converted into disordered active oxyhydroxide phase with optimized oxygen intermediates adsorption under low OER overpotentials, thus boosting the intrinsic electrocatalytic activity.

The agricultural waste (Goji branch) was pyrolyzed into biochars with one-step potassium hydroxide (KOH) activation under different processing conditions. The biochars were first characterized in structural features and functional groups and then evaluated for adsorptive performance with methylene blue as a model pollutant. Different adsorption models were applied to fit the adsorption process and reveal the possible mechanisms. The adsorption capacity was found to strongly correlate (R2 = 0.9642) with the surface area of the biochars, among which biochar K50%W29%C-700 (pyrolysis at 700 °C in the presence of 50 % KOH and 29 % water) possessed the largest surface area (1378 m2/g) and exhibited the highest adsorption capacity (769 mg/g) compared to its homologous products. Biochar K50%W29%C-700 also showed excellent recyclability and potent adsorption capacity toward other common organic pollutants. The results suggest that traces of water in agricultural wastes could significantly intensify the KOH-involved activation efficiency of producing porous biochar.

Developing efficient and affordable electrocatalysts for the sluggish oxygen evolution reaction (OER) remains a significant barrier that needs to be overcome for the practical applications of hydrogen production via water electrolysis, transforming CO2 to value-added chemicals, and metal-air batteries. Recently, hydroxides have shown promise as electrocatalysts for OER. In situ or operando techniques are particularly indispensable for monitoring the key intermediates together with understanding the reaction process, which is extremely important for revealing the formation/OER catalytic mechanism of hydroxides and preparing cost-effective electrocatalysts for OER. However, there is a lack of comprehensive discussion on the current status and challenges of studying these mechanisms using in situ or operando techniques, which hinders our ability to identify and address the obstacles present in this field. This review offers an overview of in situ or operando techniques, outlining their capabilities, advantages, and disadvantages. Recent findings related to the formation mechanism and OER catalytic mechanism of hydroxides revealed by in situ or operando techniques are also discussed in detail. Additionally, some current challenges in this field are concluded and appropriate solution strategies are provided.

Developing a fast and highly active oxygen evolution reaction (OER) catalyst to change energy kinetics technology is essential for making clean energy. Herein, we prepare three-dimensional (3D) hollow Mo-doped amorphous FeOOH (Mo-FeOOH) based on the precatalyst MoS2 /FeC2 O4 via in situ reconstruction strategy. Mo-FeOOH exhibits promising OER performance. Specifically, it has an overpotential of 285 mV and a durability of 15 h at 10 mA cm-2 . Characterizations indicate that Mo was included inside the FeOOH lattice, and it not only modifies the electronic energy levels of FeOOH but also effectively raises the inherent activity of FeOOH for OER. Additionally, in situ Raman analysis indicates that FeC2 O4 gradually transforms into the FeOOH active site throughout the OER process. This study provides ideas for designing in situ reconstruction strategies to prepare heteroatom doping catalysts for high electrochemical activity.

Bone is a highly hierarchical complex structure that consists of organic and mineral components represented by collagen molecules (CM) and hydroxyapatite crystals (HAC), respectively. The nanostructure of bone can significantly affect its mechanical properties. There is a lack of understanding how collagen fibrils (CF) in different orientations may affect the mechanical properties of the bone. The objective of this study is to investigate the effect of interaction, orientation, and hydration on atomic models of the bone composed of collagen helix (CH) and HAC, using molecular dynamics simulations and therefrom bone-related disease origins. The results demonstrate that the mechanical properties of the bone are affected significantly by the orientation of the CF attributed to contact areas at 0° and 90° models. The molecular dynamics simulation illustrated that there is significant difference (p < 0.005) in the ultimate tensile strength and toughness with respect to the orientation of the hydrated and un-hydrated CF. Additionally, the results indicated that having the force in a longitudinal direction (0°) provides more strength compared with the CF in the perpendicular direction (90°). Furthermore, the results show that substituting glycine (GLY) with any other amino acid affects the mechanical properties and strength of the CH, collagen−hydroxyapatite interface, and eventually affects the HAC. Generally, hydration dramatically influences bone tissue elastic properties, and any change in the orientation or any abnormality in the atomic structure of either the CM or the HAC would be the main reason of the fragility in the bone, affecting bone pathology.

The triclinic structures of poly[(μ4-4,4\'-bi-phenyldi-carboxyl-ato)di-μ-hydroxido-dicobalt], [Co2(C14H8O4)(OH)2] n , and poly[(μ4-4,4\'-bi-phenyldi-carboxyl-ato)di-μ-hydroxido-dinickel], [Ni2(C14H8O4)(OH)2] n , were established using laboratory X-ray powder diffraction data. These structures, as well as that of poly[(μ4-4,4\'-bi-phenyldi-carboxyl-ato)di-μ-hydroxido-dimanganese], [Mn2(C14H8O4)(OH)2] n , were optimized using density functional techniques. The structure of di-ammonium 4,4\'-bi-phenyldi-carboxyl-ate, 2NH4 +·C14H8O4 2-, was also solved using laboratory powder data. The Mn and Co compounds are isostructural: the octa-hedral MO6 groups share edges to form chains running parallel to the c-axis. These chains share corners (OH groups) to link into layers lying parallel to the bc plane. The hydroxyl groups do not participate in hydrogen bonds. The structure of (NH4)2BPDC consists of alternating layers of BPDC and ammonium ions lying parallel to the ab plane. Each hydrogen atom of the ammonium ions in (NH4)2BPDC participates in a strong N-H⋯O hydrogen bond.