<i>In situ</i> observation of pH change during water splitting in neutral pH conditions: impact of natural convection driven by buoyancy effects

Obata, Keisuke; Krol, Roel van de; Schwarze, Michael; Schomäcker, Reinhard; Abdi, Fatwa F.

doi:10.1039/d0ee01760d

Cited by 77 publications

(81 citation statements)

References 78 publications

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“…4 ). Taking into account that the pH of unbuffered electrolytes in the vicinity of the cathode during electrolysis can be further elevated by a minimum of 1 unit 35 , the hypothesized transformation is possible from the thermodynamic point of view. Besides that, the ICP-OES characterization results also confirm that Fe's release by the mechanism speculated above is possible as, after 20 h HER treatment, the Fe content in 1.0 M KOH increased from 27.3 to 48.7 ppb.…”

Section: Resultsmentioning

confidence: 99%

Revealing the effect of electrocatalytic performance boost during hydrogen evolution reaction on free-standing SWCNT film electrode

Kordek-Khalil

Janas

Rutkowski

2021

Sci Rep

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Large-scale sustainable hydrogen production by water electrolysis requires a highly active yet low-cost hydrogen evolution reaction (HER) electrocatalyst. Conductive carbon nanomaterials with high surface areas are promising candidates for this purpose. In this contribution, single-walled carbon nanotubes (SWCNTs) are assembled into free-standing films and directly used as HER electrodes. During the initial 20 h of electrocatalytic performance in galvanostatic conditions, the films undergo activation, which results in a gradual overpotential decrease to the value of 225 mV. Transient physicochemical properties of the films at various activation stages are characterized to reveal the material features responsible for the activity boost. Results indicate that partial oxidation of iron nanoparticles encapsulated in SWCNTs is the major contributor to the activity enhancement. Furthermore, besides high activity, the material, composed of only earth-abundant elements, possesses exceptional performance stability, with no activity loss for 200 h of galvanostatic performance at − 10 mA cm−2. In conclusion, the work presents the strategy of engineering a highly active HER electrode composed of widely available elements and provides new insights into the origins of electrocatalytic performance of SWCNT-based materials in alkaline HER.

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Section: Resultsmentioning

confidence: 99%

Revealing the effect of electrocatalytic performance boost during hydrogen evolution reaction on free-standing SWCNT film electrode

Kordek-Khalil

Janas

Rutkowski

2021

Sci Rep

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“…The model solves the transient equation for conservation of ionic species. 46,58,59 Diffusion, migration and convection determines the flux, j i , of ionic species. The reaction term, R i , accounts for the equilibrium reaction of water (2 H 2 O −− −− H + + OH -) and dissociation of SNARF (SNARF -1 −− −− SNARF -2 + H + ) within the liquid domain.…”

Section: Discussionmentioning

confidence: 99%

Visualization of Concentration Gradients and Colloidal Dynamics under Electrodiffusiophoresis

Wang

Behdani

Batista

2022

Preprint

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In this work, we present an experimental study of the dynamics of charged colloids under direct currents and gradients of chemical species (electrodiffusiophoresis). In our approach, we simultaneously visualize the development of concentration polarization and the ensuing dynamics of charged colloids near electrodes. With the aid of confocal microscopy and fluorescent probes, we show that the passage of current through water confined between electrodes, separated about a hundred microns, results in significant pH gradients. Depending on the current density and initial conditions, steep pH gradients develop, thus becoming a significant factor in the behavior of charged colloids. Furthermore, we show that steep pH gradients induce the focusing of charged colloids away from both electrodes. Our results provide the experimental basis for further development of models of electrodiffusiophoresis and the design of non-equilibrium strategies for materials fabrication.

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“…After 10 s of illumination, there is a small current increase. Since the volume above the illuminated area of 1.0 × 0.25 mm 2 is only 0.02 µ L, due to the fluidic dimensions and no-flow conditions during the first 10 s, a reduced mass transfer can lead to a depletion of reaction partners, decreasing the current [33]. Hence, providing fresh solution with starting the flow after 10 s, the current increases to a nearly constant value of 1.04 µ A, as Similarly to the H + ions generated by the enzymatic reaction, it is possible to visualize the photoelectrocatalytically produced protons with differential chemical images by the LAPS.…”

Section: Ph Manipulation With Laementioning

confidence: 99%

Light-Addressable Actuator-Sensor Platform for Monitoring and Manipulation of pH Gradients in Microfluidics: A Case Study with the Enzyme Penicillinase

et al. 2021

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The feasibility of light-addressed detection and manipulation of pH gradients inside an electrochemical microfluidic cell was studied. Local pH changes, induced by a light-addressable electrode (LAE), were detected using a light-addressable potentiometric sensor (LAPS) with different measurement modes representing an actuator-sensor system. Biosensor functionality was examined depending on locally induced pH gradients with the help of the model enzyme penicillinase, which had been immobilized in the microfluidic channel. The surface morphology of the LAE and enzyme-functionalized LAPS was studied by scanning electron microscopy. Furthermore, the penicillin sensitivity of the LAPS inside the microfluidic channel was determined with regard to the analyte’s pH influence on the enzymatic reaction rate. In a final experiment, the LAE-controlled pH inhibition of the enzyme activity was monitored by the LAPS.

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In situ observation of pH change during water splitting in neutral pH conditions: impact of natural convection driven by buoyancy effects

Abstract: Photoelectrochemical water splitting in near-neutral pH conditions offers a safe and sustainable way to produce solar fuels, but operation at near-neutral pH is challenging because of the added concentration overpotentials...

Cited by 77 publications

References 78 publications

Revealing the effect of electrocatalytic performance boost during hydrogen evolution reaction on free-standing SWCNT film electrode

Revealing the effect of electrocatalytic performance boost during hydrogen evolution reaction on free-standing SWCNT film electrode

Visualization of Concentration Gradients and Colloidal Dynamics under Electrodiffusiophoresis

Light-Addressable Actuator-Sensor Platform for Monitoring and Manipulation of pH Gradients in Microfluidics: A Case Study with the Enzyme Penicillinase

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