The anode oxygen evolution reaction (OER) is known to largely limit the efficiency of electrolyzers owing to its sluggish kinetics. While crystalline metal oxides are promising as OER catalysts, ...their amorphous phases also show high activities. Efforts to produce amorphous metal oxides have progressed slowly, and how an amorphous structure benefits the catalytic performances remains elusive. Now the first scalable synthesis of amorphous NiFeMo oxide (up to 515 g in one batch) is presented with homogeneous elemental distribution via a facile supersaturated co‐precipitation method. In contrast to its crystalline counterpart, amorphous NiFeMo oxide undergoes a faster surface self‐reconstruction process during OER, forming a metal oxy(hydroxide) active layer with rich oxygen vacancies, leading to superior OER activity (280 mV overpotential at 10 mA cm−2 in 0.1 m KOH). This opens up the potential of fast, facile, and scale‐up production of amorphous metal oxides for high‐performance OER catalysts.
Amorphous NiFeMo oxide (up to 515 g one batch) with homogeneous elemental distribution was synthesized through a facile supersaturated co‐precipitation method. The amorphous NiFeMo oxide undergoes rapid surface self‐reconstruction during OER that forms a metal oxy(hydroxide) active layer with oxygen vacancies, enabling efficient OER catalysis.
Hydroxide exchange membrane fuel cells offer possibility of adopting platinum-group-metal-free catalysts to negotiate sluggish oxygen reduction reaction. Unfortunately, the ultrafast hydrogen ...oxidation reaction (HOR) on platinum decreases at least two orders of magnitude by switching the electrolytes from acid to base, causing high platinum-group-metal loadings. Here we show that a nickel-molybdenum nanoalloy with tetragonal MoNi
phase can catalyze the HOR efficiently in alkaline electrolytes. The catalyst exhibits a high apparent exchange current density of 3.41 milliamperes per square centimeter and operates very stable, which is 1.4 times higher than that of state-of-the-art Pt/C catalyst. With this catalyst, we further demonstrate the capability to tolerate carbon monoxide poisoning. Marked HOR activity was also observed on similarly designed WNi
catalyst. We attribute this remarkable HOR reactivity to an alloy effect that enables optimum adsorption of hydrogen on nickel and hydroxyl on molybdenum (tungsten), which synergistically promotes the Volmer reaction.
The roles of soluble Fe and Ni species in the alkaline oxygen evolution reaction (OER) at a Ni anode are reported. The Fe impurities in the electrolyte turn out to be insufficient to directly improve ...the OER activity. The Ni(OH)2/NiOOH film undergoes chemical dissolution to give a stable Ni(ii) species that plays a hindering role in the OER.
The anode oxygen evolution reaction (OER) is known to largely limit the efficiency of electrolyzers owing to its sluggish kinetics. While crystalline metal oxides are promising as OER catalysts, ...their amorphous phases also show high activities. Efforts to produce amorphous metal oxides have progressed slowly, and how an amorphous structure benefits the catalytic performances remains elusive. Now the first scalable synthesis of amorphous NiFeMo oxide (up to 515 g in one batch) is presented with homogeneous elemental distribution via a facile supersaturated co‐precipitation method. In contrast to its crystalline counterpart, amorphous NiFeMo oxide undergoes a faster surface self‐reconstruction process during OER, forming a metal oxy(hydroxide) active layer with rich oxygen vacancies, leading to superior OER activity (280 mV overpotential at 10 mA cm−2 in 0.1 m KOH). This opens up the potential of fast, facile, and scale‐up production of amorphous metal oxides for high‐performance OER catalysts.
Entwicklungshilfe: Amorphes NiFeMo‐Oxid (bis 515 g pro Charge) mit homogener Elementverteilung wurde durch einfache Coabscheidung aus übersättigter Lösung erhalten. Während einer Sauerstoffentwicklungsreaktion (OER) erfährt es eine rasche Oberflächen‐Selbstrekonstruktion, wobei eine aktive Metalloxy(hydroxid)‐Schicht mit Sauerstoff‐Fehlstellen entsteht, was eine effiziente OER‐Katalyse ermöglicht.
Developing atomically precise catalysts for hydrogen evolution reaction (HER) will help understand the catalytic reaction mechanisms for guiding the synthesis of new HER catalysts. A Cu-based ...metal-organic framework (CuII-MOF) consisting of trinuclear mixed-ligand units was prepared under hydrothermal conditions, and the structure, morphology, and elemental composition were characterized by (single crystal) XRD, TEM, SEM, XPS, BET, TGA and ATR-FTIR. Doping of 9.2 wt% CuII-MOF powder into the carbon paste electrode caused a roughly 440 mV positive shift of the HER potential at 10 mA cm−2 in 1.0 M H2SO4. The CuII-MOF showed a high working stability due to the dual-ligand-protected Cu active centers. The intrinsic catalytic mechanism was investigated by Tafel slope analysis, solid state electrochemistry and electrochemical impedance spectroscopy. The CuII ions in the CuII-MOF are successively reduced through two single-electron steps over a potential range of 0.7 to 0.1 V vs. RHE to form single-atom Cu0 active centers, on which adsorbed H atoms can be generated with a positive onset potential of about 100 mV vs. RHE through a following chemical redox reaction. The mechanistic findings point out the necessity and feasibility of developing bicomponent or bifunctional MOF-based catalysts to efficiently accelerate both the first and second electron transfer steps of HER.
Display omitted
•A CuII-MOF single crystal as a new HER catalyst is synthesized and characterized.•The catalyst brings about a positive onset potential of 100 mV vs. RHE for the first electron transfer of HER.•The formation and spillover of adsorbed H atoms are investigated.•A new insight into the mechanism how the Cu active sites catalyze HER.
The roles of soluble Fe and Ni species in the alkaline oxygen evolution reaction (OER) at a Ni anode are reported. The Fe impurities in the electrolyte turn out to be insufficient to directly improve ...the OER activity. The Ni(OH)
2
/NiOOH film undergoes chemical dissolution to give a stable Ni(
ii
) species that plays a hindering role in the OER.
Ni(
ii
) in electrolyte hinders the alkaline oxygen evolution reaction on a nickel anode.
Ammonia（NH3） plays vital roles in new particle formation and atmospheric chemistry. Although previous studies have revealed that it also influences the formation of secondary organic aerosols（SOA） ...from ozonolysis of biogenic and anthropogenic volatile organic compounds（VOCs）, the influence of NH3 on particle formation from complex mixtures such as vehicle exhausts is still poorly understood. Here we directly introduced gasoline vehicles exhausts（GVE） into a smog chamber with NH3 absorbed by denuders to examine the role of NH3 in particle formation from GVE. We found that removing NH3 from GVE would greatly suppress the formation and growth of particles. Adding NH3 into the reactor after 3 h photo-oxidation of GVE, the particle number concentration and mass concentrations jumped explosively to much higher levels, indicating that the numbers and mass of particles might be enhanced when aged vehicle exhausts are transported to rural areas and mixed with NH3-rich plumes. We also found that the presence of NH3 had no significant influence on SOA formation from GVE. Very similar oxygen to carbon（O：C） and hydrogen to carbon（H：C） ratios resolved by aerosol mass spectrometer with and without NH3 indicated that the presence of NH3 also had no impact on the average carbon oxidation state of SOA from GVE.
This study aimed to assess the reliability of experienced Chinese orthodontists in evaluating treatment outcome and to determine the correlations between three diagnostic information sources. ...Sixty-nine experienced Chinese orthodontic specialists each evaluated the outcome of orthodontic treatment of 108 Chinese patients. Three different information sources： study casts （SC）, lateral cephalometric X-ray images （LX） and facial photographs （PH） were generated at the end of treatment for 108 patients selected randomly from six orthodontic treatment centers throughout China. Six different assessments of treatment outcome were made by each orthodontist using data from the three information sources separately and in combination. Each assessment included both ranking and grading for each patient. The rankings of each of the 69 judges for the 108 patients were correlated with the rankings of each of the other judges yielding 13 873 Spearman rs values, ranging from -0.08 to ＋0.85. Of these, 90% were greater than 0.4, showing moderate-to-high consistency among the 69 orthodontists. In the combined evaluations, study casts were the most significant predictive component （R2=0.86, P〈0.000 1）, while the inclusion of lateral cephalometric films and facial photographs also contributed to a more comprehensive assessment （R2=0.96, P〈0.000 1）. Grading scores for SC＋LX and SC＋PH were highly significantly correlated with those for SC＋LX＋PH （r（SC＋LX）vs.（SC＋LX＋PH）=0.96, r（SC＋PH）vs.（SC＋LX＋PH）=0.97）, showing that either SC＋LX or SC＋PH is an excellent substitute for all three combined assessment,
AIM：To evaluate the efficacy and safety of emergency transcatheter arterial embolization （ETAE） for patients with acute massive duodenal ulcer hemorrhage. METHODS：Twenty-nine consecutive patients ...with acute massive bleeding of duodenal ulcer were admitted to our hospital from 2006 to 2011. Superselective angiography of the celiac and gastroduodenal arteries was performed to find out the bleeding sites before ETAE, then, embolotherapy was done with gelatin sponge particles or microstrips via a 5 French angio-graphic catheter or 3 French microcatheter. After ETAE, further superior mesenteric arteriography was under-taken in case collateral circulation supplied areas of the duodenal ulcer. Technical and clinical success rates were analyzed. Changes in the mucous membrane were observed using endoscopy following ETAE. RESULTS：Angiography showed active bleeding with extravasation of contrast medium in seven cases with a 24% positive rate of celiac artery bleeding, and in 19 cases with a 65.5% rate of gastroduodenal artery bleeding. There were no angiographic signs of bleeding in three patients who underwent endoscopy prior to ETAE. Twenty-six patients achieved immediate hemostasis and technical success rate reached 90%. No hemostasis was observed in 27 patients within 30 d after ETAE and clinical success rate was 93%. Recurrent hemorrhage occurred in two patients who drank a lot of wine who were treated by a second embolotherapy in the same way. Five patients underwent transient ischem with light abdominal pain under xiphoid, spontaneous restoration without special treatment. No mucous necrosis happened to 29 cases for ischem of gastroduodenal arteries embolized. CONCLUSION：ETAE is an effective and safe measure to control acute massive bleeding of duodenal ulcer.
Background Improving the success rate of ureteroscopic lithotripsy for proximal ureteral stones is the hot issue in this field. Here we reported our experience on the treatment of proximal ureteral ...stones.
Methods From 2005 to 2010, 187 consecutive patients with proximal ureteral stones who underwent ureteroscopic lithotripsy were enrolled. The initial 52 patients treated by semi-rigid ureteroscope alone were classified as group 1. The subsequent 135 patients treated by semi-rigid ureteroscope with the aid of stone basket and flexible ureteroscope were classified as group 2.
Results In group 1, the overall stone-free rate was 67.3%. By a single procedure of ureteroscopic lithotripsy using a semi-rigid instrument, patients with ureteral stones below the 4th lumbar vertebra level achieved 91.7% stone-free rate, which was only 50% in patients with stones above the 4th lumbar vertebra level. Conversion to open surgery occurred in two patients since ureteral perforation was observed. In group 2, the stone-free rate achieved 93.2% with the aid of an N-Trap basket, which was significantly higher than that of patients without the aid of the basket （51.6%）. Flexible ureteroscope was subsequently used in patients with fragment migration, thus making the overall success rate in group 2 increases to 97.0%.
Conclusions Ureteroscopic lithotripsy is a safe and efficacious treatment for proximal ureteral stones. A single procedure of ureteroscopic lithotripsy using semi-rigid ureteroscope could achieve a satisfactory stone-free rate in patients with proximal ureteral stones below the 4th lumbar vertebra level. However, patients with ureteral stones above the 4th lumbar vertebra level experienced higher stone-migration rate, which would decrease the success rate. Fortunately, the stone-free state could possibly be achieved with the aid of an N-trap basket and flexible ureteroscope.
PDF
