Quantification of the Effect of an External Magnetic Field on Water Oxidation with Cobalt Oxide Anodes.

Here, we quantify the effect of an external magnetic field (ß) on the oxygen evolution reaction (OER) for a cobalt oxide|fluorine-doped tin oxide coated glass (CoOx|FTO) anode. A bespoke apparatus enables us to precisely determine the relationship between magnetic flux density (ß) and OER activity at the surface of a CoOx|FTO anode. The apparatus includes a strong NdFeB magnet (ßmax = 450 ± 1 mT) capable of producing a magnetic field of 371 ± 1 mT at the surface of the anode. The distance between the magnet and the anode surface is controlled by a linear actuator, enabling submillimeter distance positioning of the magnet relative to the anode surface. We couple this apparatus with a finite element analysis magnetic model that was validated by Hall probe measurements to determine the value of ß at the anode surface. At the largest tested magnetic field strength of ß = 371 ± 1 mT, a 4.7% increase in current at 1.5 V vs the normal hydrogen electrode (NHE) and a change in the Tafel slope of 14.5 mV/dec were observed. We demonstrate through a series of OER measurements at sequential values of ß that the enhancement consists of two distinct regions. The possible use of this effect to improve the energy efficiency of commercial water electrolyzers is discussed, and major challenges pertaining to the accurate measurement of the phenomenon are demonstrated.

Direct H2O2 Synthesis, without H2 Gas.

We report here the direct hydrogenation of O2 gas to form hydrogen peroxide (H2O2) using a membrane reactor without H2 gas. Hydrogen is sourced from water, and the reactor is driven by electricity. Hydrogenation chemistry is achieved using a hydrogen-permeable Pd foil that separates an electrolysis chamber that generates reactive H atoms, from a hydrogenation chamber where H atoms react with O2 to form H2O2. Our results show that the concentration of H2O2 can be increased ∼8 times (from 56.5 to 443 mg/L) by optimizing the ratio of methanol-to-water in the chemical chamber, and through catalyst design. We demonstrate that the concentration of H2O2 is acutely sensitive to the H2O2 decomposition rate. This decomposition rate can be minimized by using AuPd alloy catalysts instead of pure Pd. This study presents a new pathway to directly synthesize H2O2 using water electrolysis without ever using H2 gas.

Electrocatalysts Derived from Copper Complexes Transform CO into C2+ Products Effectively in a Flow Cell.

Electrochemical reactors that electrolytically convert CO2 into higher-value chemicals and fuels often pass a concentrated hydroxide electrolyte across the cathode. This strongly alkaline medium converts the majority of CO2 into unreactive HCO3 - and CO3 2- byproducts rather than into CO2 reduction reaction (CO2RR) products. The electrolysis of CO (instead of CO2 ) does not suffer from this undesirable reaction chemistry because CO does not react with OH- . Moreover, CO can be more readily reduced into products containing two or more carbon atoms (i. e., C2+ products) compared to CO2 . We demonstrate here that an electrocatalyst layer derived from copper phthalocyanine (CuPc) mediates this conversion effectively in a flow cell. This catalyst achieved a 25 % higher selectivity for acetate formation at 200 mA/cm2 than a known state-of-art oxide-derived Cu catalyst tested in the same flow cell. A gas diffusion electrode coated with CuPc electrolyzed CO into C2+ products at high rates of product formation (i. e., current densities ≥200 mA/cm2 ), and at high faradaic efficiencies for C2+ production (FEC2+ ; >70 % at 200 mA/cm2 ). While operando Raman spectroscopy did not reveal evidence of structural changes to the copper molecular complex, X-ray photoelectron spectroscopy suggests that the catalyst undergoes conversion to a metallic copper species during catalysis. Notwithstanding, the ligand environment about the metal still impacts catalysis, which we demonstrated through the study of a homologous CuPc bearing ethoxy substituents. These findings reveal new strategies for using metal complexes for the formation of carbon-neutral chemicals and fuels at industrially relevant conditions.

Physical Separation of H2 Activation from Hydrogenation Chemistry Reveals the Specific Role of Secondary Metal Catalysts.

An electrocatalytic palladium membrane reactor (ePMR) uses electricity and water to drive hydrogenation without H2 gas. The device contains a palladium membrane to physically separate the formation of reactive hydrogen atoms from hydrogenation of the unsaturated organic substrate. This separation provides an opportunity to independently measure the hydrogenation reaction at a surface without any competing H2 activation or proton reduction chemistry. We took advantage of this feature to test how different metal catalysts coated on the palladium membrane affect the rates of hydrogenation of C=O and C=C bonds. Hydrogenation occurs at the secondary metal catalyst and not the underlying palladium membrane. These secondary catalysts also serve to accelerate the reaction and draw a higher flux of hydrogen through the membrane. These results reveal insights into hydrogenation chemistry that would be challenging using thermal or electrochemical hydrogenation experiments.

Strain Influences the Hydrogen Evolution Activity and Absorption Capacity of Palladium.

Strain engineering can increase the activity and selectivity of an electrocatalyst. Tensile strain is known to improve the electrocatalytic activity of palladium electrodes for reduction of carbon dioxide or dioxygen, but determining how strain affects the hydrogen evolution reaction (HER) is complicated by the fact that palladium absorbs hydrogen concurrently with HER. We report here a custom electrochemical cell, which applies tensile strain to a flexible working electrode, that enabled us to resolve how tensile strain affects hydrogen absorption and HER activity for a thin film palladium electrocatalyst. When the electrodes were subjected to mechanically-applied tensile strain, the amount of hydrogen that absorbed into the palladium decreased, and HER electrocatalytic activity increased. This study showcases how strain can be used to modulate the hydrogen absorption capacity and HER activity of palladium.

Axial EBIC oscillations at core/shell GaAs/Fe nanowire contacts.

Electron beam induced current (EBIC) measurements were carried out in situ in the scanning electron microscope on free-standing GaAs/Fe core-shell nanowires (NWs), isolated from the GaAs substrate via a layer of aluminum oxide. The excess current as a function of the electron beam energy, position on the NW, and scan direction were collected, together with energy dispersive x-ray spectroscopy. A model that included the effects of beam energy and Fe thickness predicted an average collection efficiency of 60%. Small spatial oscillations in the EBIC current were observed, that correlated with the average Fe grain size (30 nm). These oscillations likely originated from lateral variations in the interfacial oxide thickness, affecting the resistance, barrier potentials, and density of minority carrier recombination traps.

Regrowth mechanism for oxide isolation of GaAs nanowires.

Oxide-isolated GaAs nanowires (NWs) were obtained through a lithography-free method in which axial growth of NWs coated in aluminum oxide (Al2O3) is restarted using an annealing step. NWs are grown using the vapor-liquid-solid method and coated in nanometer thin oxide films using atomic layer deposition. Continued growth at the oxide-coated nanoparticle (NP) occurs after the thermally-induced fracture of the oxide during annealing. This oxide fracture is observed to depend on NP diameter, oxide thickness and annealing temperature. A thermal expansion mismatch model for stresses on the oxide shell is put forward to explain these results.

Oxygen and Bis(3',5')-cyclic Dimeric Guanosine Monophosphate Binding Control Oligomerization State Equilibria of Diguanylate Cyclase-Containing Globin Coupled Sensors.

Bacteria sense their environment to alter phenotypes, including biofilm formation, to survive changing conditions. Heme proteins play important roles in sensing the bacterial gaseous environment and controlling the switch between motile and sessile (biofilm) states. Globin coupled sensors (GCS), a family of heme proteins consisting of a globin domain linked by a central domain to an output domain, are often found with diguanylate cyclase output domains that synthesize c-di-GMP, a major regulator of biofilm formation. Characterization of diguanylate cyclase-containing GCS proteins from Bordetella pertussis and Pectobacterium carotovorum demonstrated that cyclase activity is controlled by ligand binding to the heme within the globin domain. Both O2 binding to the heme within the globin domain and c-di-GMP binding to a product-binding inhibitory site (I-site) within the cyclase domain control oligomerization states of the enzymes. Changes in oligomerization state caused by c-di-GMP binding to the I-site also affect O2 kinetics within the globin domain, suggesting that shifting the oligomer equilibrium leads to broad rearrangements throughout the protein. In addition, mutations within the I-site that eliminate product inhibition result in changes to the accessible oligomerization states and decreased catalytic activity. These studies provide insight into the mechanism by which ligand binding to the heme and I-site controls activity of GCS proteins and suggests a role for oligomerization-dependent activity in vivo.

Visualization of CO2 electrolysis using optical coherence tomography.

Electrolysers offer an appealing technology for conversion of CO2 into high-value chemicals. However, there are few tools available to track the reactions that occur within electrolysers. Here we report an electrolysis optical coherence tomography platform to visualize the chemical reactions occurring in a CO2 electrolyser. This platform was designed to capture three-dimensional images and videos at high spatial and temporal resolutions. We recorded 12 h of footage of an electrolyser containing a porous electrode separated by a membrane, converting a continuous feed of liquid KHCO3 to reduce CO2 into CO at applied current densities of 50-800 mA cm-2. This platform visualized reactants, intermediates and products, and captured the strikingly dynamic movement of the cathode and membrane components during electrolysis. It also linked CO production to regions of the electrolyser in which CO2 was in direct contact with both membrane and catalyst layers. These results highlight how this platform can be used to track reactions in continuous flow electrochemical reactors.

Bioelectrocatalysis with a palladium membrane reactor.

Enzyme catalysis is used to generate approximately 50,000 tons of value-added chemical products per year. Nearly a quarter of this production requires a stoichiometric cofactor such as NAD+/NADH. Given that NADH is expensive, it would be beneficial to regenerate it in a way that does not interfere with the enzymatic reaction. Water electrolysis could provide the proton and electron equivalent necessary to electrocatalytically convert NAD+ to NADH. However, this form of electrocatalytic NADH regeneration is challenged by the formation of inactive NAD2 dimers, the use of high overpotentials or mediators, and the long-term electrochemical instability of the enzyme during electrolysis. Here, we show a means of overcoming these challenges by using a bioelectrocatalytic palladium membrane reactor for electrochemical NADH regeneration from NAD+. This achievement is possible because the membrane reactor regenerates NADH through reaction of hydride with NAD+ in a compartment separated from the electrolysis compartment by a hydrogen-permselective Pd membrane. This separation of the enzymatic and electrolytic processes bypasses radical-induced NAD+ degradation and enables the operator to optimize conditions for the enzymatic reaction independent of the water electrolysis. This architecture, which mechanistic studies reveal utilizes hydride sourced from water, provides an opportunity for enzyme catalysis to be driven by clean electricity where the major waste product is oxygen gas.

Diagnosis of ST-elevation myocardial infarction in the presence of left bundle branch block with the ST-elevation to S-wave ratio in a modified Sgarbossa rule.

STUDY OBJECTIVE: Sgarbossa's rule, proposed for the diagnosis of acute myocardial infarction in the presence of left bundle branch block, has had suboptimal diagnostic utility. We hypothesize that a revised rule, in which the third Sgarbossa component (excessively discordant ST-segment elevation as defined by ≥5 mm of ST-segment elevation in the setting of a negative QRS) is replaced by one defined proportionally by ST-segment elevation to S-wave depth (ST/S ratio), will have better diagnostic utility for ST-segment elevation myocardial infarction (STEMI) equivalent, using documented coronary occlusion on angiography as reference standard. METHODS: We collected admission ECGs for all patients with an acutely occluded coronary artery and left bundle branch block at 3 institutions. The ECGs of emergency department patients with chest pain or dyspnea and left bundle branch block, but without coronary occlusion, were used as controls. The R or S wave, whichever was most prominent, and ST segments, relative to the PR segment, were measured to the nearest 0.5 mm. The ST/S ratio was calculated for each lead that has both discordant ST deviation of greater than or equal to 1 mm and an R or S wave of opposite polarity; others were set to 0. The cut point for the most negative ST/S ratio with at least 90% specificity was determined. The revised rule is unweighted, requiring just 1 of 3 criteria. Diagnostic utilities of the original and revised Sgarbossa rules were computed and compared. McNemar's test was used to compare sensitivities and specificities. RESULTS: The study and control groups included 33 and 129 ECGs, respectively. The cut point selected for relative discordant ST-segment elevation was -0.25. Excessive absolute discordant ST-segment elevation of 5 mm was present in at least one lead in 30% of ECGs in patients with confirmed coronary occlusion versus 9% of the control group, whereas excessive relative discordant ST-segment elevation less than -0.25 was present in 79% vs. 9% [corrected].Sensitivity of the revised rule in which ST-segment elevation with an ST/S ratio less than or equal to -0.25 replaces ST-segment elevation greater than or equal to 5 mm was significantly greater than either the weighted (P<.001) or unweighted (P=.008) Sgarbossa rule: 91% (95% confidence interval [CI] 76% to 98%) versus 52% (95% CI 34% to 69%) versus 67% (95% CI 48% to 82%). Specificity of the revised rule was lower than that of the weighted rule (P=.002) and similar to that of the unweighted rule (P=1.0): 90% (95% CI 83% to 95%) versus 98% (95% CI 93% to 100%) versus 90% (95% CI 83% to 95%). Positive and negative likelihood ratios for the revised rule were 9.0 (95% CI 8.0 to 10) and 0.1 (95% CI 0.03 to 0.3). The revised rule was significantly more accurate than both the weighted (16% difference; 95% CI 5% to 27%) and unweighted (12% difference; 95% CI 2% to 22%) Sgarbossa rules. CONCLUSION: Replacement of the absolute ST-elevation measurement of greater than or equal to 5 mm in the third component of the Sgarbossa rule with an ST/S ratio less than -0.25 greatly improves diagnostic utility of the rule for STEMI. An unweighted rule using this criterion resulted in excellent prediction for acute coronary occlusion.

Electrolytic conversion of carbon capture solutions containing carbonic anhydrase.

The electrolysis of carbon capture solutions bypasses energy-intensive CO2 recovery steps that are often required to convert CO2 into value-added products. We report herein an electrochemical flow reactor that converts carbon capture solutions containing carbonic anhydrase enzymes into carbon-based products. Carbonic anhydrase enzymes benefit CO2 capture by increasing the rate of reaction between CO2 and weakly alkaline solutions by 20-fold. In this study, we reduced CO2-enriched bicarbonate solutions containing carbonic anhydrase ("enzymatic CO2 capture solutions") into CO at current densities of 100 mA cm-2. This result demonstrated how to electrolyse enzymatic CO2 capture solutions, but the selectivity for CO production was two-thirds less than bicarbonate solutions without carbonic anhydrase. This reduction in performance occurred because carbonic anhydrase deactivated the catalyst surface. A carbon microporous layer was found to suppress this deactivation.

High-Efficiency Perovskite Solar Cells with Sputtered Metal Contacts.

Sputter deposition produces dense, uniform, adhesive, and scalable metal contacts for perovskite solar cells (PSCs). However, sputter deposition damages the other layers of the PSC. We here report that the damage caused by sputtering metal contacts can be reversed by aerial oxidation. We support this claim by making PSCs sputtered with Au contacts that exhibit higher efficiencies (18.7%) and stabilities than those made with thermally evaporated Au contacts (18.4%). We performed a series of experiments that show that the post-sputtering oxidation step reconstructs the molecular order of the hole transport layer (HTL) and reverses Au atom diffusion into the HTL. This potential restoration was previously neglected in PSC fabrication recipes because metal contact deposition is generally performed after the HTL oxidation. This result is important for scaling PSCs because sputtering is a superior method for manufacturing optimal-quality coatings or large-area devices.

A self-driving laboratory advances the Pareto front for material properties.

Useful materials must satisfy multiple objectives, where the optimization of one objective is often at the expense of another. The Pareto front reports the optimal trade-offs between these conflicting objectives. Here we use a self-driving laboratory, Ada, to define the Pareto front of conductivities and processing temperatures for palladium films formed by combustion synthesis. Ada discovers new synthesis conditions that yield metallic films at lower processing temperatures (below 200 °C) relative to the prior art for this technique (250 °C). This temperature difference makes possible the coating of different commodity plastic materials (e.g., Nafion, polyethersulfone). These combustion synthesis conditions enable us to to spray coat uniform palladium films with moderate conductivity (1.1 × 105 S m-1) at 191 °C. Spray coating at 226 °C yields films with conductivities (2.0 × 106 S m-1) comparable to those of sputtered films (2.0 to 5.8 × 106 S m-1). This work shows how a self-driving laboratoy can discover materials that provide optimal trade-offs between conflicting objectives.

Design rules for high mobility xanthene-based hole transport materials.

Tunable and highly conductive hole transport materials are crucial for the performance of organic electronics applications such as organic light emitting diodes and perovskite solar cells. For commercial applications, these materials' requirements include easy synthesis, high hole mobility, and highly tuned and compatible electronic energy levels. Here, we present a systematic study of a recently discovered, easy-to-synthesize class of spiro[fluorene-9,9'-xanthene]-based organic hole transport materials. Systematic side group functionalization allows us to control the HOMO energy and charge carrier mobility. Analysis of the bulk simulations enables us to derive design rules for mobility enhancement. We show that larger functional groups (e.g. methyl) decrease the conformational disorder due to steric effects and thus increase the hole mobility. Highly asymmetric or polar side groups (e.g. fluorine), however, increase the electrostatic disorder and thus reduce the hole mobility. These generally applicable design rules will help in the future to further optimize organic hole transport materials.

Solution-Deposited Solid-State Electrochromic Windows.

Commercially available electrochromic (EC) windows are based on solid-state devices in which WO3 and NiOx films commonly serve as the EC and counter electrode layers, respectively. These metal oxide layers are typically physically deposited under vacuum, a time- and capital-intensive process when using rigid substrates. Herein we report a facile solution deposition method for producing amorphous WO3 and NiOx layers that prove to be effective materials for a solid-state EC device. The full device containing these solution-processed layers demonstrates performance metrics that meet or exceed the benchmark set by devices containing physically deposited layers of the same compositions. The superior EC performance measured for our devices is attributed to the amorphous nature of the NiOx produced by the solution-based photodeposition method, which yields a more effective ion storage counter electrode relative to the crystalline NiOx layers that are more widely used. This versatile method yields a distinctive approach for constructing EC windows.

Acute myocardial infarction and renal dysfunction: a high-risk combination.

BACKGROUND: Survival is poor in patients with acute myocardial infarction (MI) who also have severe renal disease. Less is known about the outcome of acute MI in patients with mild to moderate renal insufficiency. OBJECTIVE: To compare outcomes after acute MI in patients with varying levels of renal disease and in patients without renal failure. DESIGN: Retrospective cohort study. SETTING: Academic medical center. PATIENTS: 3106 total patients admitted with acute MI and end-stage renal disease (n = 44), severe renal insufficiency (creatinine clearance < 0.59 mL/s [<35 mL/min]) (n = 391), moderate renal dysfunction (creatinine clearance > or = 0.59 mL/s [<35 mL/min] but < or =0.84 mL/s [< or =50 mL/min]) (n = 491), mild chronic renal insufficiency (creatinine clearance > 0.84 mL/s [>50 mL/min] but < or =1.25 mL/s [< or =75 mL/min]) (n = 860), or no renal disease (n = 1320). MEASUREMENTS: Clinical characteristics, treatment strategies, and short- and long-term survival were compared after patients were stratified by creatinine clearance. RESULTS: In-hospital mortality rates were 2% in patients with normal renal function, 6% in those with mild renal failure, 14% in those with moderate renal failure, 21% in those with severe renal failure, and 30% in those with end-stage renal disease (P < 0.001). Compared with patients without renal disease, similar adjusted trends were present for postdischarge death in patients with end-stage renal disease (hazard ratio, 5.4 [95% CI, 3.0 to 9.7]; P < 0.001), severe renal insufficiency (hazard ratio, 1.9 [CI, 1.2 to 3.0]; P = 0.006), moderate renal dysfunction (hazard ratio, 2.2 [CI, 1.5 to 3.3]; P < 0.001), and mild chronic renal insufficiency (hazard ratio, 2.4 [CI, 1.7 to 3.3]; P < 0.001). Patients with renal failure received adjunctive and reperfusion therapies less frequently than those with normal renal function (P < 0.001). Postdischarge death was less likely in patients who received acute reperfusion therapy (odds ratio, 0.7 [CI, 0.6 to 0.9]), aspirin (odds ratio, 0.7 [CI, 0.5 to 0.8]), and beta-blocker therapy (odds ratio, 0.7 [CI, 0.6 to 0.9]). CONCLUSION: Patients with renal failure are at increased risk for death after acute MI and receive less aggressive treatment than patients with normal renal function.

Baseline comorbidities and treatment strategy in elderly patients are associated with outcome of cardiogenic shock in a community-based population.

BACKGROUND: Cardiogenic shock (CGS) historically results in high inhospital mortality, particularly in elderly patients. Factors that contribute to increased mortality and treatment strategies that improve short- and long-term outcomes in patients with CGS remain to be established. METHODS: The study consisted of 1263 consecutive patients with acute myocardial infarction admitted from Olmsted County, Minn, during the period 1988 to 2000; of these, 73 (6%) developed cardiogenic shock. Short- and long-term mortality was compared between the elderly and younger populations in both shock and nonshock groups. RESULTS: In patients with acute myocardial infarction, age of > or =65 years was associated with increased long-term mortality for nonshock patients (unadjusted relative risk [RR] 5.23, 95% CI 4.10-6.67, P <.001) and to a lesser degree in patients with cardiogenic shock (unadjusted RR 2.02, 95% CI 1.12-3.65, P =.02). Among cardiogenic shock patients, estimated survival at 1 and 5 years for elderly patients was 38% and 24%, respectively, and in younger patients, 57% and 52%, respectively. When adjusted for confounding variables, elderly noncardiogenic shock patients had significantly increased long-term mortality (adjusted RR 4.38, 95% CI 3.42-5.61, P <.001) compared to younger nonshock patients. In contrast, elderly patients with cardiogenic shock demonstrated a weaker trend toward worse outcomes (adjusted RR 1.80, 95% CI 1.00-3.27, P =.051) compared to younger patients with shock. CONCLUSIONS: The relationship between age and long-term mortality is stronger among patients who do not develop cardiogenic shock. Advanced age was not found to be as strong a risk factor for survival in patients with cardiogenic shock; comorbidities and less aggressive treatment appear to be the major factors resulting in poor outcomes in the elderly patient with cardiogenic shock.

Effect of diabetes on the mortality risk of cardiogenic shock in a community-based population.

OBJECTIVE: To examine the mortality of diabetic vs nondiabetic patients with anterior myocardial infarction (AMI) among the subsets of this population who did and did not develop cardiogenic shock. PATIENTS AND METHODS: The study population consisted of a consecutive series of 1263 Olmsted County, Minnesota, patients admitted to the coronary care unit at the Mayo Clinic in Rochester, Minn, between January 1, 1988, and July 31, 2000. Of these patients, 73 met the criteria for cardiogenic shock during their hospitalization. In-hospital and postadmission mortality were compared between diabetic and nondiabetic patients within the cardiogenic shock and nonshock patient groups, respectively. RESULTS: In patients with AMI and cardiogenic shock, diabetes was associated with a trend for increased in-hospital mortality (odds ratio, 2.82; 95% confidence interval [CI], 0.90-9.92; P = .08). In 73 patients with cardiogenic shock, estimated survival at 1, 3, and 5 years was 25%, 17%, and 17%, respectively, for diabetic patients, and 50%, 44%, and 36%, respectively, for nondiabetic patients (P = .046). The association between diabetic patients and increased long-term mortality was stronger in patients with cardiogenic shock than in patients without cardiogenic shock (adjusted relative risk, 2.08; 95% CI, 1.11-3.90; P = .02). In diabetic patients without cardiogenic shock, estimated survival at 1, 3, and 5 years was low, at 75%, 61%, and 45%, respectively, compared with 83%, 76%, and 69%, respectively, for nondiabetic patients (adjusted relative risk, 1.29; 95% CI, 1.02-1.62; P = .03). CONCLUSION: The presence of diabetes as a comorbidity in patients with AMI appears to be associated with increased mortality compared with nondiabetic patients, and this relationship may be potentially magnified in patients who develop cardiogenic shock.