Jeongwon Kim

Inset: pH value of the solution with CO2 flushing as a function of the time aerated. All electrolysis in this system was performed in 1 M NH3 in 5 M KOH solution at 60oC. (c) The amount (mL) and (d) faradaic efficiency (%) of each gas produced during operation of ammonia electrolysis time over 200 min discharge at 200 mA. e) Chronopotentiometric profile in three-electrode configuration system and (f) Hydrogen production per current consumption during continuous discharge at 200 mA. Figure 7-12 a).

Introduction

• Research background
• Polymer electrolyte membrane fuel cell
• Metal-air batteries
• Metal-CO 2 batteries
• Electrochemical reaction in devices
• The Sabatier principle and volcano plots
• Oxygen reduction reaction
• Oxygen evolution reaction
• Hydrogen evolution reaction
• Thesis structure

In either proton exchange membrane fuel cells (PEMFCs) or metal–air batteries (MAB), oxygen reduction reaction (ORR) is one of the important electrochemical processes for the efficient operation of whole devices. On the contrary, for metals that bind oxygen too weakly, the activity is limited by proton electron transfer to O2* or cleavage of the O-O bond.

A New Strategy for Outstanding Performance and Durability in Acidic

Experimental

• Preparation of Pt/FeN-GnPs composite
• Characterization of electrochemical measurements
• Polymer electrolyte membrane fuel cell tests

For the FeN-GnPs-based cathodes, the charge density of the catalyst was 1.5 mg cm-2 and the binder was 1 mg cm-2. For the Pt/FeN-GnPs-based cathodes, the charge density of the catalyst was 0.23 mgPtcm-2 and the binder was 1 mg cm-2.

Result and discussion

• Characterization of Pt/FeN-GnPs catalyst
• Electrochemical properties for oxygen reduction reaction
• Structural analysis between before and after operation for ORR
• Electric configuration of targe catalyst
• Electrochemical performances in an acidic PEM fuel cell
• Stability measurements in an acidic PEM fuel cell

Face-centered cubic (fcc) crystalline platinum is measured as Pt (111) and Pt (200) facets along with the graphitic carbon peak in the XRD patterns of Pt/FeN-GnPs. Furthermore, the limiting current of Pt/FeN-GnPs is even larger than that of the commercial Pt/C at the high overpotential region.

Conclusions

Synergistic Coupling Derived Cobalt Oxide with Nitrogenated Holey Two-

Introduction

The Co3O4/Fe@C2N NP catalyst exhibits comparable Tafel slope for ORR and OER to that of commercial Pt/C and IrO2 catalysts, as well as excellent electrochemical stability caused by the bonding interaction between the Co3O4 NPs and the C2N framework. Together with these favorable properties, we have demonstrated that the NP Co3O4/Fe@C2N catalyst is a promising bifunctional catalyst for metal–air batteries, and the synergistic coupling of the metal oxide with the C2N framework represents an approach for the development of advanced energy conversion catalysts.

Experimental

• Synthesis of Fe@C 2 N
• Synthesis of NP Co 3 O 4 /Fe@C 2 N
• Structural characterization and electrochemical tests
• Zinc (Zn)-air cell assembly and measurements

The exposed planes of the Co3O4 phase on the Fe@C2N structure with NP morphology are well controlled to be a (111) plane, leading to superior bifunctional activities for the ORR and the OER compared to that of their counterpart catalysts with different exposed faces (e.g. the cubic and octahedral nanostructures of Co3O4). Fe@C2N was dispersed in the anhydrous ethanol (EtOH) where the concentration of the Fe@C2N in EtOH solution was ~0.3 mg/ml.

Result and discussion

• Structural Characterization
• Electrocatalytic activities
• Electrochemical characterization
• Alkaline Metal (Zn, Li) -Air Batteries

114 mV dec−1, resp., corresponding to electroactivities following the order of Co3O4/Fe@C2N > IrO2 > Fe@C2N NPs. Based on the fitted results, the relative content (Olattice/Oad) of NP Co3O4/Fe@C2N and composite Co3O4+Fe@C2N are 1.94 and 2.93, respectively. In Figure 3-14c, the Co3O4+Fe@C2N composition is also evaluated and compared to the Co3O4/Fe@C2N NP catalyst.

The specific capacity normalized to the mass of reacted Zn was 790.1 mAh g-1Zn for NP Co3O4/Fe@C2N catalyst. The electrochemical performances of the NP Co3O4/Fe@C2N and Pt/C+IrO2 catalysts were also evaluated in hybrid Li-air batteries.

Conclusions

Cloud-like graphene nanoplatelets on Nd0.5Sr0.5CoO3-δNanorods as an efficient bifunctional electrocatalyst for hybrid Li-Air batteries. An efficient oxygen evolution catalyst for hybrid lithium-air batteries: almond stick type composite of perovskite and cobalt oxide. Enables highly efficient, flexible and rechargeable quasi-solid-state Zn-air batteries via catalyst engineering and electrolyte functionalization.

2D-Metal Zeolitic-Imidazolate-Frame-(Zif)-Dual-Metal Bifunctional Air Electrode with Ultra High Electrochemical Properties for Zinc-Air Rechargeable Batteries. Carbon Nanosheets Containing Discrete Co-Nx-By-C Active Sites for Efficient Oxygen Electrocatalysis and Zn-Air Rechargeable Batteries.

Efficient CO 2 utilization via a hybrid Na-CO 2 system based on CO 2

• Introduction
• Experimental
• Half-cell configured electrochemical analysis
• Characterization techniques
• Full-cell measurements
• Result and discussion
• The proposed hybrid Na-CO 2 cell and its reaction mechanism
• Half-cell configured electrochemical analysis
• Performance and stability of hybrid Na-CO 2 cell
• Reversibility of hybrid Na-CO 2 cell
• Conclusions

Morphological analysis of the working electrode before and after the discharge process in Na-CO2 hybrid. A titanium wire was used as a cathode current collector and the aqueous electrolytes were saturated with CO2. Further, the pH of the NaOH solution saturated with CO2 after 1000 hours of operation was investigated and determined to be 6.62, indicating that the pH of the solution is stably maintained over 1000 hours (Figure 4-7).

The additional XRD profiles of the powder obtained by different drying processes are shown in Figure 4-10. The present work indicates the new hydrogen generation technology from the use of CO2 and is significant because it proves the additional dissolution of CO2 during the discharge process, but further work is needed to investigate the CO2 conversion efficiency and power density of the hybrid Na-CO2 cell improve.

Highly Efficient CO 2 Utilization via Novel Aqueous Zn or Al-CO 2 Systems

Introduction

Experimental

• Catalysts preparation and characterization techniques
• Half-cell analysis
• Full-cell measurements

The microstructure of the prepared catalysts was investigated by scanning electron microscopy (SEM, Nova FE-SEM). The structural identification of the catalysts was carried out by X-ray powder diffraction (XRD) (Bruker diffractometer, Cu Kα radiation) at a scan rate of 1 omin-1. Half-cell measurements were continued in three-electrode configuration using a platinum wire used as both working electrode and counter electrode with Ag/AgCl (saturated KCl filled) reference electrode in 1 M potassium hydroxide (KOH, Sigma-Aldrich Co.) aqueous solution and sea water (taken from the sea of ​​Ulsan and filtered to remove visible impurities).

Each catalyst was prepared in a catalyst ink by dispersing 10 mg of the catalyst in 1 mL of a binder solution ethanol : isopropyl alcohol : 5 wt% Nafion solution (Sigma-Aldrich Co., volumetric ratio) followed by ' a bath sonication process. Then, RDE profiles were measured by dropping 5 mL of the drop-coated catalyst ink onto glassy carbon disk electrode, where the area is 0.1256 cm2, at a scan rate of 5 mV s-1.

Result and discussion

• The proposed aqueous Zn- or Al-CO 2 system and its reaction mechanism 74
• Electrochemical performances and in-operando quantitatively analysis
• Structural analysis of product and feed gas after long-term stability test

This spontaneous dissolution of CO2 contributes to the acidification of the aqueous solution and the lowering of the pH value. An apparent oxygen reduction peak appeared near -0.15 V (vs. Ag/AgCl) in 1 M KOH saturated with O2, which probably corresponds to the oxygen reduction reaction (ORR) at the Pt electrode.[12]Typical diffusion controlled region. with the current limit was observed close to -0.4 V from the O2 mass transfer limit in the ORR profile. [11c, 12b] In the lower potential region, steep reduction profiles were observed around -1.05 V under O2 and N2 saturated conditions, corresponding to typical hydrogen evolution reactions (HER). [13] In contrast, for the CO2 saturated condition, the initial HER potential shifted positive by 0.4 V due to the lowered pH due to CO2 dissolution. This performance indicates that this Zn-CO2 system has a facile and highly efficient cathodic reaction compared to the highest performance reported for metal-CO2 cells (i.e. Zn-CO2 cell based on CO2-HCOOH interconversion: 5.5 mW cm -2 at 11 mA cm-2). [5j] The I-V polarization profiles obtained at different catalyst loading densities and KOH solution concentration are presented in Figure 5-7. It is important to note that this cell uses CO2 to generate not only electricity but also H2 gas in a quasi-neutral state (Note: H2 is a by-product during discharge.

We investigated the continuity of the system when the electrolyte is saturated with the carbonate ions. In terms of reaction efficiency, that is, the efficiency of HER, it can be understood as follows.

Conclusions

Typical credit card was offered to compare the size of the cell (Any personal information or card number is not shown). c) Screen captured image of raw data of Zn-CO2 cell performances measured by small H-type cell and large-scale H-type cell.

Indirect Surpassing CO 2 Utilization in Membrane-free CO 2 Battery 94

Experimental

• Purchasing chemicals
• Materials synthesis
• Characterization techniques
• Half-cell configured electrochemical testing
• Electrode preparation for half-cell testing
• Full-cell measurements
• Computational method

The gas generated during the discharge process was analyzed with a gas chromatograph with thermal conductivity detector (GC-TCD), using argon as a carrier gas (GC-2010 Plus, SHIMADZU Co.) using an H-type cell. The membrane-free Mg-CO battery is composed of Mg metal/aqueous electrolyte/gas evolution. The gas generation electrode was fabricated by dropwise applying the catalyst ink (Pt/C+_IrO2 ink) onto a gas diffusion layer (Toray carbon paper, TGP-H-090, Fuel Cell Store Co.) with a loading density of 2 mg cm _2 .

-dimensional electrochemical modeling is performed by simulating the physical appearance of the Mg-CO2 battery system. a) Schematic of the Mg-CO2 battery model, (b) Meshes containing 0.1 million tetrahedral elements, (c) Electronic potential distribution at , (d) Spatial distribution of current density along the length of the magnesium metal, and (e) Corresponding current density distribution in the electrodes. Therefore, the potential drop due to concentration overvoltage is not significant even at high current density, which can be confirmed in the polarization profile of the Mg-CO2 battery.

Result and discussion

• The proposed battery and electrochemical mechanism
• Half-cell configured electrochemical analysis
• Full-cell performances of membrane-free Mg-CO 2 battery
• Structure and morphology analysis after discharge process
• Reversibility of membrane-free Mg-CO 2 battery

To investigate the effects of CO2 dissolution, the polarization curve of the discharge in the N2-saturated solution was also recorded, as shown in Figure 6-5. The chronopotentiometry profile of the MF Mg-CO2 battery was measured at a current density of 20 mA cm-2 (Figure 6-6b), which shows a stable reduction potential (Ecell=~ about 1.0 V) over 35 hours. Climate ions in the electrolyte have led not only to stable oxidation of the Mg electrode, but also to an increase in the charging kinetics of the MF Mg-CO2 battery.

The performance of the MF Mg-CO2 battery was tested at different flow rates. As shown in Figure 6-14, the concentration of Mg ions in the electrolyte solution gradually increased due to the partial corrosion of the Mg electrode even without charging for the first 2 hours.

Conclusions

Kim, Highly efficient CO2 use via aqueous zinc or aluminum CO2 systems for hydrogen gas development and electricity production, Angew. Archer, The O2-assisted Al/CO2 electrochemical cell: a system for CO2 capture/conversion and electrical power generation, Sci. Zhou, Metal – CO2 batteries on the move: CO2 from polluting gas to energy source, Adv.

Dai, Highly rechargeable lithium-CO2 batteries with a boron and nitrogen doped graphene cathode, Angew. Lee, Iridium oxide dendrite as a highly efficient dual electrocatalyst for water splitting and H2O2 sensing, J.

A Rigorous Electrochemical Ammonia Electrolysis Protocol with In-

• Introduction
• Experimental
• Electrochemical Pt deposition
• Electrochemical measurements
• Gas chromatography analysis
• Result and discussion
• Procedure for synthesis of electrode
• Structural analysis for AOR electrode
• Electrochemical activities for optimized AOR progress
• Full-cell measurements for AOR
• In-operando quantitative analysis with gas chromatography
• Conclusions

From the CV measurements, the CP-Pt electrode and the 100 CV-Pt electrode showed a similar peak current density of 182 and 176 mA cm-2, respectively. Ammonia oxidation kinetics also increased with 500 CV-Pt electrodes as shown in Figure 7-4b. Therefore, the CV deposition process was optimized for 500 CV-Pt electrode according to the ammonia oxidation performance regarding the maximum current density and kinetics for AOR.

Among the electrocatalysts, the 500 CV-Pt electrode exhibits excellent durability performance for 10 h at a current density of 50 mA cm-2. After stability using the "initial electrode", the peak current density of the electrode was dramatically reduced (denoted After stability test with blue color).

General conclusions and outlook

Conclusions and Outlook