Influence of Water Transport across Microscale Bipolar Interfaces on the Performance of Direct Borohydride Fuel Cells

Zhongyang Wang; Mrinmay Mandal; Shrihari Sankarasubramanian; Garrett Huang; Paul A. Kohl; Vijay K. Ramani

doi:10.1021/acsaem.0c00145

Influence of Water Transport across Microscale Bipolar Interfaces on the Performance of Direct Borohydride Fuel Cells

Zhongyang Wang, Mrinmay Mandal, Shrihari Sankarasubramanian, Garrett Huang, Paul A. Kohl, Vijay K. Ramani

Research output: Contribution to journal › Article › peer-review

45 Scopus citations

Abstract

Direct borohydride fuel cells (DBFCs) can operate at double the voltage of proton exchange membrane fuel cells (PEMFCs) by employing an alkaline NaBH4 fuel feed and an acidic H2O2 oxidant feed. The pH-gradient-enabled microscale bipolar interface (PMBI) facilitates the creation and maintenance of an alkaline environment at the anode and an acidic environment at the cathode for the borohydride oxidation and peroxide reduction reactions. However, given the need to dissociate water at the interface to ensure ionic conduction, PMBI can be efficient only when anion exchange ionomer (AEI) moieties enable fast water transport for autoprotolysis. Herein, a series of polynorbornene-based AEIs with a range of water uptake values are examined to unravel the optimum water uptake required to enable high performance DBFCs. The DBFC with PMBI configuration containing the optimal AEI composition delivers a current density of 302 mA cm-2 at 1.5 V and a peak power density of 580 mW cm-2 at 1 V. This AEI composition exhibits high hydroxide ionic conductivity of 90.7 mS cm-1 at 80 °C with an IEC of 2.01 mequiv g-1 and demonstrates impressive chemical stability by retaining 98.75% of its initial ionic conductivity after immersion into anolyte (3 M KOH and 1.5 M NaBH4) at 70 °C for 536 h.

Original language	English
Pages (from-to)	4449-4456
Number of pages	8
Journal	ACS Applied Energy Materials
Volume	3
Issue number	5
DOIs	https://doi.org/10.1021/acsaem.0c00145
State	Published - May 26 2020

Keywords

alkaline stability
anion exchange ionomer
bipolar interface
direct borohydride fuel cell
liquid fuel cell
water transport

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10.1021/acsaem.0c00145

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title = "Influence of Water Transport across Microscale Bipolar Interfaces on the Performance of Direct Borohydride Fuel Cells",

abstract = "Direct borohydride fuel cells (DBFCs) can operate at double the voltage of proton exchange membrane fuel cells (PEMFCs) by employing an alkaline NaBH4 fuel feed and an acidic H2O2 oxidant feed. The pH-gradient-enabled microscale bipolar interface (PMBI) facilitates the creation and maintenance of an alkaline environment at the anode and an acidic environment at the cathode for the borohydride oxidation and peroxide reduction reactions. However, given the need to dissociate water at the interface to ensure ionic conduction, PMBI can be efficient only when anion exchange ionomer (AEI) moieties enable fast water transport for autoprotolysis. Herein, a series of polynorbornene-based AEIs with a range of water uptake values are examined to unravel the optimum water uptake required to enable high performance DBFCs. The DBFC with PMBI configuration containing the optimal AEI composition delivers a current density of 302 mA cm-2 at 1.5 V and a peak power density of 580 mW cm-2 at 1 V. This AEI composition exhibits high hydroxide ionic conductivity of 90.7 mS cm-1 at 80 °C with an IEC of 2.01 mequiv g-1 and demonstrates impressive chemical stability by retaining 98.75\% of its initial ionic conductivity after immersion into anolyte (3 M KOH and 1.5 M NaBH4) at 70 °C for 536 h.",

keywords = "alkaline stability, anion exchange ionomer, bipolar interface, direct borohydride fuel cell, liquid fuel cell, water transport",

author = "Zhongyang Wang and Mrinmay Mandal and Shrihari Sankarasubramanian and Garrett Huang and Kohl, \{Paul A.\} and Ramani, \{Vijay K.\}",

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doi = "10.1021/acsaem.0c00145",

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T1 - Influence of Water Transport across Microscale Bipolar Interfaces on the Performance of Direct Borohydride Fuel Cells

AU - Wang, Zhongyang

AU - Mandal, Mrinmay

AU - Sankarasubramanian, Shrihari

AU - Huang, Garrett

AU - Kohl, Paul A.

AU - Ramani, Vijay K.

PY - 2020/5/26

Y1 - 2020/5/26

N2 - Direct borohydride fuel cells (DBFCs) can operate at double the voltage of proton exchange membrane fuel cells (PEMFCs) by employing an alkaline NaBH4 fuel feed and an acidic H2O2 oxidant feed. The pH-gradient-enabled microscale bipolar interface (PMBI) facilitates the creation and maintenance of an alkaline environment at the anode and an acidic environment at the cathode for the borohydride oxidation and peroxide reduction reactions. However, given the need to dissociate water at the interface to ensure ionic conduction, PMBI can be efficient only when anion exchange ionomer (AEI) moieties enable fast water transport for autoprotolysis. Herein, a series of polynorbornene-based AEIs with a range of water uptake values are examined to unravel the optimum water uptake required to enable high performance DBFCs. The DBFC with PMBI configuration containing the optimal AEI composition delivers a current density of 302 mA cm-2 at 1.5 V and a peak power density of 580 mW cm-2 at 1 V. This AEI composition exhibits high hydroxide ionic conductivity of 90.7 mS cm-1 at 80 °C with an IEC of 2.01 mequiv g-1 and demonstrates impressive chemical stability by retaining 98.75% of its initial ionic conductivity after immersion into anolyte (3 M KOH and 1.5 M NaBH4) at 70 °C for 536 h.

AB - Direct borohydride fuel cells (DBFCs) can operate at double the voltage of proton exchange membrane fuel cells (PEMFCs) by employing an alkaline NaBH4 fuel feed and an acidic H2O2 oxidant feed. The pH-gradient-enabled microscale bipolar interface (PMBI) facilitates the creation and maintenance of an alkaline environment at the anode and an acidic environment at the cathode for the borohydride oxidation and peroxide reduction reactions. However, given the need to dissociate water at the interface to ensure ionic conduction, PMBI can be efficient only when anion exchange ionomer (AEI) moieties enable fast water transport for autoprotolysis. Herein, a series of polynorbornene-based AEIs with a range of water uptake values are examined to unravel the optimum water uptake required to enable high performance DBFCs. The DBFC with PMBI configuration containing the optimal AEI composition delivers a current density of 302 mA cm-2 at 1.5 V and a peak power density of 580 mW cm-2 at 1 V. This AEI composition exhibits high hydroxide ionic conductivity of 90.7 mS cm-1 at 80 °C with an IEC of 2.01 mequiv g-1 and demonstrates impressive chemical stability by retaining 98.75% of its initial ionic conductivity after immersion into anolyte (3 M KOH and 1.5 M NaBH4) at 70 °C for 536 h.

KW - alkaline stability

KW - anion exchange ionomer

KW - bipolar interface

KW - direct borohydride fuel cell

KW - liquid fuel cell

KW - water transport

UR - https://www.scopus.com/pages/publications/85087943684

U2 - 10.1021/acsaem.0c00145

DO - 10.1021/acsaem.0c00145

M3 - Article

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SN - 2574-0962

VL - 3

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EP - 4456

JO - ACS Applied Energy Materials

JF - ACS Applied Energy Materials

IS - 5

ER -

Influence of Water Transport across Microscale Bipolar Interfaces on the Performance of Direct Borohydride Fuel Cells

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