Alkaline Electrolyte Solution Research Articles

Uniform Doping of Titanium in Hematite Nanorods for Efficient Photoelectrochemical Water Splitting.

Doping elements in hematite nanostructures is a promising approach to improve the photoelectrochemical (PEC) water-splitting performance of hematite photoanodes. However, uniform doping with precise control on doping amount and morphology is the major challenge for quantitatively investigating the PEC water-splitting enhancement. Here, we report on the design and synthesis of uniform titanium (Ti)-doped hematite nanorods with precise control of the Ti amount and morphology for highly effective PEC water splitting using an atomic layer deposition assisted solid-state diffusion method. We found that Ti doping promoted band bending and increased the carrier density as well as the surface state. Remarkably, these uniformly doped hematite nanorods exhibited high PEC performance with a pronounced photocurrent density of 2.28 mA/cm(2) at 1.23 V vs reversible hydrogen electrode (RHE) and 4.18 mA/cm(2) at 1.70 V vs RHE, respectively. Furthermore, as-prepared Ti-doping hematite nanorods performed excellent repeatability and durability; over 80% of the as-fabricated photoanodes reproduced the steady photocurrent density of 1.9-2.2 mA/cm(2) at 1.23 V vs RHE at least 3 h in a strong alkaline electrolyte solution.

Effects of Alkali Metal and Organic Cations on the Hydrogen Oxidation Reaction in Alkaline Electrolytes

Spectator ionic species in electrolyte solutions affect the rate and mechanism of electro-catalytic reactions. For example, it is well known that many anions, including (bi)sulfate and organic sulfonate can specifically adsorb to a platinum electrode at high potentials and affect the rate of the oxygen reduction reaction, important to fuel cell performance. If organic anions can specifically adsorb at high potentials and effect reaction rates, it should be determined if the organic cations proposed for use in new anion exchange membrane (AEM) fuel cells could specifically adsorb to platinum at low potentials and affect the rate of the hydrogen oxidation reaction. Recent evidence has shown that alkali metal cations can affect a variety of electro-catalytic reactions on platinum, including methanol oxidation, hydrogen oxidation, and oxygen reduction, but direct experimental evidence for their specific adsorption is lacking. Previously, we have used density functional theory (DFT), an ab initio quantum mechanics based technique to show that alkali metal cations can specifically adsorb to platinum and palladium electrodes at low potentials and compete with hydrogen adsorption in high pH electrolytes. We have found experimentally that the rate of the hydrogen oxidation reaction is dependent on the cation present in an alkaline electrolyte solution. We proposed and evaluated a mechanism for this effect using DFT to show alkali metal cations can specifically adsorb to the most active low index platinum facet for hydrogen oxidation, Pt(110), and can promote the adsorption of hydroxide, an important reaction intermediate. We have extended both our computational and experimental work to find that quaternary ammonium cations can also specifically adsorb to low index platinum electrode surfaces. The development of the mechanism for the effect of alkali metal cations on the rate of the hydrogen oxidation reaction and the DFT methods for simulating alkali metal cation and organic cation specific adsorption will be discussed.

Nafion Coated Lithium Ion Conducting Ceramic for Aqueous Li-Air Batteries

Protected lithium anodes use a lithium ion conducting ceramic membrane to separate the anode side and the cathode side, making it possible to use aqueous catholytes in a Li-air battery. However, this ceramic membrane is not chemically stable in acidic or alkaline electrolyte solutions. In order to extend the operational life of this protecting ceramic, modifications of its surface are needed. In this work, we coat the ceramic membrane with a thin layer of lithiated Nafion. Nafion coatings were obtained by using a doctor-blade method, with a typical thickness in the range of 6 to 10 μm. Electrochemical impedance spectroscopy showed that the Nafion coatings lead to a small increase in the membrane resistance. The coated ceramic showed better capacity and stability in cell performance when tested in extended discharge.

Ultrathin porous Co3O4 nanoplates as highly efficient oxygen evolution catalysts

Porous Co3O4 nanoplates with easily controllable pore size, pore density and crystalline size, synthesized by hydrothermal and subsequent high temperature treatment, exhibit a high electrocatalytic efficiency and stability for water oxidation in alkaline electrolyte solution.

Electrocatalytic activity of electrodeposited cobalt oxide films to produce oxygen gas from water

An electrocatalytic cobalt oxide film for water oxidation was prepared on an indium tin oxide (ITO)-coated substrate by anodic electrodeposition. Atomic force microscopy measurements revealed that numerous particles with a diameter of 100–250nm were uniformly dispersed on the ITO substrate and the particle size increased when prepared at higher temperature. Cyclic voltammograms of the Co oxide-coated ITO electrodes were measured in alkaline and neutral aqueous solutions to examine their redox characteristics and ability to catalyze water oxidation. When Co oxide was electrodeposited from solutions kept at 10, 25 and 50°C, the amount of electroactive Co oxide per unit area (Γea) was 1.06×10−8, 1.72×10−8, and 2.31×10−8molcm−2, respectively. The increase in Γea accompanied the increase in particle size observed with rising deposition temperature. Quantitative analyses of O2 gas produced by water electrolysis were carried out under potentiostatic conditions using these Co oxide-modified electrodes and a bare ITO electrode for comparison. For the Co oxide-coated electrode prepared at 10°C, the amount of O2 evolved by electrolysis for 2h at 1.3V vs. Ag/AgCl was 1.3×10−5molcm−2 in alkaline electrolyte solution and 1.52×10−5molcm−2 in neutral electrolyte solution containing phosphate ions. In addition, when the Co oxide-coated electrode treated at 450°C was used, the amount of O2 evolved by the electrolysis increased to 2.58×10−5molcm−2 in the neutral electrolyte solution containing phosphate ions, resulting from a stable catalytic current.

Preparation of LaMnO3-CNF and Its Activity for Oxygen Electrode Reaction in Alkaline Electrolyte Solution

Cathode catalysts with low overpotential for oxygen electrode reaction including oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are required for the batteries that air and an alkaline electrolyte are used. For this purpose, a kind of perovskite metal oxides is promised. Although the electric conductivity is low, LaMnO3shows relatively high activity for both ORR and OER [1, 2]. To support the electric conductivity, some kinds of carbon must be required to practical use. Among the carbon materials, carbon nano fiber, which is partially used in lithium battery, is considered to be favorable because of adequate electric conductivity, high hydrophobicity, low surface area and quite low amount of surface functional groups.In this study, we attempted to prepare a new composite catalyst, that LaMnO3particles are supported on carbon nano fiber, and evaluated catalyst activity for ORR and OER. La(NO3)3 and Mn(NO3)2 aqueous solutions were respectively prepared at desired concentration and well mixed. Then, the solution was poured into (CH3)4NOH aqueous solution. After that, CNF (VGCF, SHOWA DENKO K.K.) was immediately added to the solution and stirred for 1 hour at room temperature. The product was washed with pure water and dried at 120oC for 12 hour. Finally, it was calcined under Ar atmosphere at 600oC for 5, 10 and 20 hour, 800 and 1000oC for 5 hour (600-5, 600-10, 600-20, 800-5 and 1000-5) to obtain LaMnO3 and CNF composites (LaMnO3-CNT).X-ray diffraction (XRD) was used to identify the product. The product was observed by field emission scanning electron microscope (FE-SEM). ORR and OER activity were evaluated in 0.1 mol dm-3 and 6.0 mol dm-3KOH solution by using glassy carbon or Ti substrate. Figure 1 shows FE-SEM image of 800-5. As indicated by allows in this figure, CNF is covered with particles of LaMnO3. In addition, the product that only edge parts were covered with particles and the product that was not covered with particles occasionally.Figure 2 shows XRD patterns of 800-5 and 1000-5. The patterns of 600-5, 600-10, 600-20 and 800-5 show the formation of LaMnO3 and the different crystallite size. In the case of 1000-5, La2O3and MnO are confirmed, suggesting that oxygen in the products should be consumed by CNF oxidation.Figure 3 shows hydrodynamic voltammograms of the samples in 0.1 mol dm-3KOH solution. Reduction current originated from ORR is shown below 0.85 V. From this point of view, 600-10 shows the highest on-set potential (lowest overpotential) among the samples. The detail including OER activity of the samples will be also presented. This work was supported by “Advanced Low Carbon Technology Research and Development Program (ALCA)” of Japan Science and Technology Agency (JST). [1] J Suntivich, H A. Gasteiger, N Yabuuchi, H Nakanishi, J B. Goodenough and Y Shao-Horn, DOI: 10.1038/NCHEM.1069.[2]J O’M. Bockris and Takaaki Otagawa,J Electronchem.Soc. :ELECTROCHEMICAL SCIENCE AND TECHNOLOGY p.290-302 Vol. 131,No. 2.(1984)

Modeling of Triple-Phase Boundary in Air Electrodes for Metal-Air Secondary Batteries Using Partially Immersed Electrodes

Introduction There has been increasing interest in metal-air secondary batteries such as Zn-air secondary batteries, Al-air secondary batteries, etc. These batteries are expected to have high energy densities because they can utilize ambient air as their positive electrode material. They are also expected to be very safe because they can utilize aqueous electrolyte solutions. Therefore, they are very attractive power sources for electric vehicles. However, there are many problems at negative and positive electrodes, and in alkaline electrolyte solution for practical use. Among them, the low power density of air electrode is one of the most serious problems as power sources for electric vehicles. In air electrode, the electrochemical reactions of oxygen reduction and oxygen evolution only occur at the regions where the three species, the electron, the electrolyte and the oxygen, have contact with each other, so-called triple-phase boundary. Therefore, well-fabricated triple-phase boundaries can lead to great improvement of the power densities. However, it is difficult to investigate the properties of the triple-phase boundaries by using the practical gas-diffusion electrodes, because their microstructures are very complicated. Therefore, partially immersed electrode system have been applied for the investigation of the properties of triple-phase boundaries[1 - 3]. In these systems, mass transport of the gases and ions will be very similar to those in the catalyst layers. In this research, we use partially immersed Pt-supported glassy carbon electrode and partially immersed Pt interdigitated array electrode (Fig. 1) systems in alkaline condition for modeling of triple-phase boundary in air electrodes for metal-air secondary batteries. Experimental A three-electrode electrochemical cell was used for electrochemical measurements. Preparation of partially immersed electrode for working electrode was done by fully immersing Pt-supporting area of electrode (h = 0 mm) and vertically raising electrode by micrometer head to h = 10 mm. Pt wire and Hg, HgO electrode (Hg/HgO) were used as counter and reference electrodes, respectively. Solutions of 0.10 ~ 10 mol dm- 3 KOH (saturated with mixed gas of O2 and Ar ) were used as an electrolyte. Potentiostatic measurements were carried out under the mixed gas atmosphere. Steady-state oxygen reduction currents were measured. Segmental currents of Pt interdigitated array electrode were also measured simultaneously with I-V converter. Results and discussion Figure 2 shows the segmental currents of Pt interdigitated array electrode in 1.0 mol dm- 3 KOH (saturated with mix gas of O2 and Ar (P o2= 0.2 atm) ). Relatively low segmental currents were observed from 0.0 mm to 2.9 mm. This is because intrinsic meniscus was formed at these regions. It is assumed that electrolyte thin film was formed at upper regions exceeding 3.0 mm. In these regions, current crowding at the low segments was observed. The higher the applied potential was and the lower the electrolyte conductivity was, the greater the current crowding became. This suggests that ohmic-loss should be caused at electrolyte thin film. Limiting current was also observed at low segments of electrolyte thin film. With the increase of the oxygen partial pressure, the limiting currents were increased. This indicates that oxygen diffusion should be a rate-determining step at the regions where local overpotentials were sufficiently high. Reference H. J. Maget et al., J. Electrochem.Soc. 112, 1034 (1965).D. N. Bennion and C. W. Tobias, J. Electrochem. Soc., 113, 589 (1966).M. Inaba, et. al., J. electrochem. Soc., 417, 105 (1996).

A portable air-aluminum power source with an alkaline electrolytic solution

The results from development of a portable air-aluminum chemical power source (AA CPS) with an alkaline electrolytic solution without any additional service circuits are presented. The feasibility of making air cathodes on the basis of a metal-carbon composite produced by the plasma method has been shown. Special features of the operational conditions of a portable AA CPS have been investigated. It has been found that the aluminum cathode passivation when aluminum hydroxide precipitates from a solution significantly restricts the specific capacity of such power sources. It was shown that it is possible to overcome the anode passivation and to considerably increase the specific capacity of an AA CPS with an alkaline electrolytic solution by means of modifying an anode alloy.

CdS quantum dots sensitized platelike WO3 photoelectrodes with a TiO2 buffer-layer

High chemical stability of WO3 photoelectrode sensitized with CdS quantum dots (QDs) was reported for the first time using nano-TiO2 as a buffer layer, permitting their stable operation for photoelectrochemical water splitting in a strongly alkaline electrolyte solution. The CdS QDs modification of the TiO2/WO3 electrode resulted in an increase in the visible light absorption and exhibited a significant improvement in photoelectrochemical performance. The photocurrent density at −0.1V (vs. Ag/AgCl) of the CdS QDs/TiO2/WO3 electrode is 10 times higher than that of the TiO2/WO3 electrode under visible light irradiation. The demonstrated strategies of utilizing a TiO2/WO3 structure to protect the WO3 electrode surface open up new opportunities for other WO3 nanostructures.

Electrolysis of ammonia for hydrogen production catalyzed by Pt and Pt-Ir deposited on nickel foam

Electrolysis of ammonia in alkaline electrolyte solution was applied for the production of hydrogen. Both Pt-loaded Ni foam and Pt-Ir loaded Ni foam electrodes were prepared by electrodeposition and served as anode and cathode in ammonia electrolytic cell, respectively. The electrochemical behaviors of ammonia in KOH solution were individually investigated via cyclic voltammetry on three electrodes, i.e. bare Ni foam electrode, Pt-loaded Ni foam electrode and Pt-Ir loaded Ni foam electrode. The morphology and composition of the prepared Ni foam electrode were analyzed by scanning electron microscopy (SEM) and X-ray diffraction (XRD). Effects of the concentration of electrolyte solution and temperature of electrolytic cell on the electrolysis reaction were examined in order to enhance the efficiency of ammonia electrolysis. The competition of ammonia electrolysis and water electrolysis in the same alkaline solution was firstly proposed to explain the changes of cell voltage with the electrolysis proceeding. At varying current densities, different cell voltages could be obtained from galvanostatic curves. The low cell voltage of 0.58 V, which is less than the practical electrolysis voltage of water (1.6 V), can be obtained at a current density of 2.5 mA/cm2. Based on some experimental parameters, such as the applied current, the resulting cell voltage and output of hydrogen gas, the power consumption per gram of H2 produced can be estimated.

An Oxalate Method for Measuring the Surface Area of Nickel Electrodes

This work establishes a new method to measure the electrochemically active surface area (AECSA) of nickel electrodes, in situ. The addition of 0.08 mol L−1 of an oxalate salt to an alkaline electrolyte solution shifts the half-wave potential of the Ni(II)/Ni(III) redox pair by about −80 mV. Further, these peaks are very narrow. The sharpest peak in this work has a full width at half maximum (FWHM) of just 11 mV. This unusual sharpness is attributed to the layered structure of nickel hydroxides and the adsorption of oxalate from the solution on the (001) surface. This is supported by attenuated total reflectance infrared (ATR-IR) peaks measured at 1265 cm−1, 1655 cm−1, and 1713 cm−1, which correspond to mononuclear bidentate oxalate bonded to nickel. At sufficiently fast potential scan rates (≥150 mV s−1), the adsorbed oxalate limits growth of the surface hydroxide to a single layer. During the reverse scan, the surface NiOOH/Ni(OH)2 reduction peak is well-separated from other electrochemical processes and may be used to accurately and precisely measure the AECSA. The error of this method is estimated at < 10%.

Seeking effective dyes for a mediated glucose–air alkaline battery/fuel cell

A significant level of power generation from an abiotic, air breathing, mediated reducing sugar–air alkaline battery/fuel cell has been achieved in our laboratories at room temperature without complicated catalysis or membrane separation in the reaction chamber. Our prior studies suggested that mass transport limitation by the mediator is a limiting factor in power generation. New and effective mediators were sought here to improve charge transfer and power density. Forty-five redox dyes were studied to identify if any can facilitate mass transport in alkaline electrolyte solution; namely, by increasing the solubility and mobility of the dye, and the valence charge carried per molecule. Indigo dyes were studied more closely to understand the complexity involved in mass transport. The viability of water-miscible co-solvents was also explored to understand their effect on solubility and mass transport of the dyes. Using a 2.0 mL solution, 20% methanol by volume, with 100 mM indigo carmine, 1.0 M glucose and 2.5 M sodium hydroxide, the glucose–air alkaline battery/fuel cell attained 8 mA cm–2 at short-circuit and 800 μW cm–2 at the maximum power point. This work shall aid future optimization of mediated charge transfer mechanism in batteries or fuel cells.

Amperometric Nitric Oxide Sensors with Enhanced Selectivity Over Carbon Monoxide via Platinum Oxide Formation Under Alkaline Conditions

An improved planar amperometric nitric oxide (NO) sensor with enhanced selectivity over carbon monoxide (CO), which represents a volatile interfering species for NO sensors that has been largely overlooked until recently, is described. Formation of an oxide film on the inner platinum working electrode via anodic polarization using an inner alkaline electrolyte solution provides the basis for improved selectivity. Cyclic voltammetry reveals that formation of an oxidized Pt film inhibits adsorption of CO to the electrode surface, which is a necessary initial step in the electrocatalytic oxidation of CO on Pt. Previous NO gas sensors that employ internal electrolyte solutions have been assembled using acidic internal solutions that inhibit the formation of a dense platinum oxide film on the working electrode surface. It is demonstrated herein that increasing the internal electrolyte pH promotes oxidized platinum film formation, resulting in improved selectivity over CO. Selectivity coefficients (log KNO,j) for sensors assembled with internal solutions at various pH values range from -0.08 at pH 2.0 to -2.06 at pH 11.7, with average NO sensitivities of 1.24 nA/μM and a limit of detection (LOD) of <1 nM.

Electrochemical hydrogen charge and discharge properties of La0.1Sr0.9Co1−yFeyO3−δ (y = 0, 0.2, 1) electrodes in alkaline electrolyte solution

In this work, we studied the hydrogen storage properties of some La0.1Sr0.9Co1−yFeyO3−δ perovskite oxides for the application in Ni–H batteries. Sr-doped La0.1Sr0.9FeO3−δ (LSF), La0.1Sr0.9CoO3−δ (LSC) and La0.1Sr0.9Co0.8Fe0.2O3−δ (LSCF) oxides were synthesized by conventional solid state method and were selected as anode materials for Ni–H battery. Their electrochemical hydrogen charge/discharge properties of oxide electrodes were investigated and exchange current density and proton diffusivity were calculated using linear polarization measurement and the potential-step method, respectively. X-ray photoelectron spectroscopy (XPS) analysis was used to show the changes in oxidation states of transition metal ions during charging/discharging process. The proton diffusion rates for LSF, LSC and LSCF were 6.73×10−17, 1.45×10−16 and 2.16×10−16cm2s−1, respectively.

Voltammetric Sensing of Amino Acids in the Presence of Cu(II) in Acidic and Alkaline Solutions

AbstractA number of amino acids have been determined at carbon film electrodes in the presence of copper. Strongly acidic, 0.1 M HCl, in the presence of 0.1 mM Cu(II), as well as alkaline, 0.1 M NaOH, solution permit successful measurement of individual amino acids, clearer separation between oxidation of Cu and Cu‐complexes occurring in alkaline solution. Electrochemical impedance showed that Cu(II) facilitates charge transfer, particularly in alkaline medium. Square wave voltammetry with preconcentration increased the response compared to linear sweep voltammetry. Protein hydrolysis rates were monitored through determination of amino acids produced by decomposition, injecting samples into alkaline electrolyte solution.

Cyanamide derived thin film on carbon nanotubes as metal free oxygen reduction reaction electrocatalyst

Nitrogen–carbon complex coated carbon nanotubes were synthesized by a metal-free post treatment of commercial carbon nanotubes with cyanamide. Following a reflux and pyrolysis procedure, these materials were found to display increased oxygen reduction reaction (ORR) activity and selectivity towards an overall four electron reduction mechanism with increasing cyanamide loadings in alkaline electrolyte solution. The ORR activity was attributed to a thin surface layer remaining after pyrolysis, most likely containing pyridinic and quaternary nitrogen species acting as the active site structures. These materials also displayed considerable ORR activity in neutral conditions, with insight into the mechanistic pathway of oxygen reduction presented. This work demonstrates that the utilization of non-precious metal precursor species is not a stringent requirement for the formation of oxygen reduction active catalyst materials and presents a sustainable class of fuel cell electrocatalyst.

Electrochromic properties of NiOOH thin films prepared by reactive sputtering in an H2O atmosphere in various aqueous electrolytes

Nickel oxyhydroxide (NiOOH) thin films were prepared by reactive sputtering using H2O as a reactive gas, and the electrochromic (EC) properties of these thin films were investigated in alkaline, neutral, and acidic aqueous electrolyte solutions. A stable EC cycling of up to 100 cycles was obtained for the NiOOH thin films in electrolyte solutions with a wide pH range of 4.1–13.5. However, the EC cycling degraded drastically after several tens of cycles in an electrolyte with pH=2.0. In the stable pH region, the NiOOH films exhibited a large transmittance change from approximately 30–90%, although the response speed slowed with decreasing pH of the electrolytes.

Synthesis and characterisation of Fe–Pt and Co–Fe–Pt nanocrystalline magnetic thin films electrodeposited from tartrate–alkaline electrolyte solution

Fe–Pt and Co–Fe–Pt nanocrystalline thin films were electrodeposited on brass substrates from a tartrate–alkaline plating bath. The composition, crystallographic structure, microstructure, surface morphology and magnetic properties of the Fe–Pt and Co–Fe–Pt alloy films were investigated. Ammonium tartrate and ammonia solution were used as complex forming additives to stabilise the Fe2+ and Co2+ ions and to enhance codeposition with platinum complexes. The as synthesised thin films were characterised by energy dispersive X-ray spectroscopy, X-ray diffraction (XRD), scanning electron microscopy, atomic force microscopy, magnetic force microscopy and alternating gradient magnetometer. The energy dispersive X-ray spectroscopy results showed that cobalt was preferentially deposited compared to iron during Co–Fe–Pt film electrodeposition. The scanning electron microscopy results showed that the microstructure of the films consisted of spherical granules and clusters. The XRD showed the formation of a disordered face centred cubic Fe–Pt phase, and all the peaks were shifted to slightly higher diffraction angles with increasing cobalt content. The average crystallite size calculated from XRD peak broadening was <10 nm. Atomic force microscopy characterisation showed that the surface roughness increased with increasing Co content in the film. The magnetic force measured by magnetic force microscopy was found to correlate to the topography of the films. The magnetic properties obtained from alternating gradient magnetometer increased with increasing surface roughness, granule size and clusters of the film. The addition of Co was found to enhance the saturation magnetisation and coercivity.

Potentiostatic electrodeposition of cuprous oxide thin films for photovoltaic applications

Potentiostatic deposition of Cu 2O thin films on glass substrates coated with F-doped SnO 2 from an alkaline electrolyte solution (pH 12.5) containing copper (II) sulfate and lactic acid was studied for fabrication of a Cu 2O/Al-doped ZnO (AZO) heterojunction solar cell. The band gap of the electrodeposited Cu 2O films was determined by photoelectrochemical measurements to be around 1.9 eV irrespective of the applied potentials. The solar cells with a glass/FTO/Cu 2O/AZO structure were fabricated by sputtering an AZO film onto the Cu 2O film followed by deposition of an Al contact by vacuum evaporation. The highest efficiency of 0.603% was obtained with a Cu 2O film deposited at −0.6 V (vs. Ag/AgCl). This was attributed to better compactness and purity of the Cu 2O film than those of the Cu 2O films deposited at other potentials.

Compatibilidad física del bicarbonato sódico con fármacos de uso frecuente en la unidad de cuidados intensivos

Introduction Acid-base disorders are associated with many diseases of the critically ill patient. Early treatment with sodium bicarbonate of these metabolic disorders is required for their normalization. This is an alkaline electrolyte solution administered by continuous or intermittent infusion. Its incompatibility due to its alkaline pH has been described, as it produces insoluble carbonate precipitation and causes carbon dioxide gas when mixed with acidic solutions. Material and method An in vitro experimental study was performed. Bicarbonate was mixed with 13 drugs simulating Y-site administration. We combined 5 ml bicarbonate with 5 ml of every drug, at highest daily concentration used. The samples were visually examined to detect color changes, cloudiness, precipitation or gas formation, pH measurement and spectrophotometric analysis at 450 nm and 620 nm. The samples were evaluated at 0, 15, 30, 60 and 120 minutes. The compatibility criteria were absence of visual changes, pH changes < 0.5 and variability of absorbance <0.01. Results We studied each drug individually and mixed with bicarbonate with 27 samples, and 135 measurements were performed. The incompatibilities did not always produce visual changes. Knowing the pH of drugs does not guarantee the compatibility of the mixture. Nitroglycerin with pH 4 is compatible with bicarbonate. Thiopental with pH 11 makes precipitation. Higher absorbances showed color changes, cloudiness and precipitation. Conclusions Bicarbonate is physically compatible with esmolol, furosemide, heparin, insulin, morphine, nimodipine, nitroglycerin and urapidil and incompatible with amiodarone, cisatracurium, haloperidol, midazolam and thiopental.