Improving electrochemical performance of PEM water electrolyzer by optimizing side-chain structure and content of ionomer

Abstract

As the proton transport channel and binder within the catalytic layer (CL), the physicochemical properties of the ionomer can affect the CL microstructure and performance of the membrane electrode assembly. In this paper, we select ionomers with different side-chain lengths and investigate the effects of the side-chain structure and content of the ionomers on the performance of membrane electrode assembly (MEA). Electrochemical tests show that at a mass ratio of 10 wt.% of ionomer/Ir (I/Ir), long-side-chain (LSC) ionomer exhibits the best performance (2.141 V@2.00 A/cm², while short-side-chain (SSC) ionomer is 2.208 V@2.00 A/cm²). The MEA containing LSC ionomer shows better electrochemical performance than the SSC at the same I/Ir mass ratio, especially at high current density. The MEA containing LSC ionomer has a larger average pore size and porosity, which indicates that it may have better mass-transfer properties. From the analysis of voltage loss, it can be seen that LSC ionomers have a smaller ohmic impedance and mass transfer resistance than SSC ionomers. In conclusion, LSC ionomers are more conducive to water-gas transport, which can provide excellent water electrolysis performance. This article focuses on the optimization of ionomer side chains and content, which can enhance PEM water electrolysis performance at lower cost.

Keywords

water electrolysis / membrane electrode assembly / anode catalytic layer / ionomer side-chain length / voltage loss

References

[1] AnderssonÖ, BörjessonP. The greenhouse gas emissions of an electrified vehicle combined with renewable fuels: Life cycle assessment and policy implications [J]. Applied Energy, 2021, 289: 116621

[2] HurtubiaB, SaumaE. Economic and environmental analysis of hydrogen production when complementing renewable energy generation with grid electricity [J]. Applied Energy, 2021, 304: 117739

[3] SteinbergM. Fossil fuel and greenhouse gas mitigation technologies [J]. International Journal of Hydrogen Energy, 1994, 19(8): 659-665

[4] ZhangZ-h, LiX-m, YinJ, et al.. Emerging hydrovoltaic technology [J]. Nature Nanotechnology, 2018, 13(12): 1109-1119

[5] XuJ-p, LiL, ZhengB-b. Wind energy generation technological paradigm diffusion [J]. Renewable and Sustainable Energy Reviews, 2016, 59: 436-449

[6] AqachmarZ, Ben SassiH, LahrechK, et al.. Solar technologies for electricity production: An updated review [J]. International Journal of Hydrogen Energy, 2021, 46(60): 30790-30817

[7] WuY, XieY-h, LiuX-l, et al.. Functional nanomaterials for selective uranium recovery from seawater: Material design, extraction properties and mechanisms [J]. Coordination Chemistry Reviews, 2023, 483: 215097

[8] ZhouB-h, GaoR-j, ZouJ-j, et al.. Surface design strategy of catalysts for water electrolysis [J]. Small, 2022, 18(27): 2202336

[9] ChenY-h, LiuC-f, XuJ-c, et al.. Key components and design strategy for a proton exchange membrane water electrolyzer [J]. Small Structures, 2023, 4(6): 2200130

[10] BabicU, NilssonE, PătruA, et al.. Proton transport in catalyst layers of a polymer electrolyte water electrolyzer: Effect of the anode catalyst loading [J]. Journal of the Electrochemical Society, 2019, 166(4): F214-F220

[11] BühlerM, HeggeF, HolzapfelP, et al.. Optimization of anodic porous transport electrodes for proton exchange membrane water electrolyzers [J]. Journal of Materials Chemistry A, 2019, 7(47): 26984-26995

[12] RozainC, MayousseE, GuilletN, et al.. Influence of iridium oxide loadings on the performance of PEM water electrolysis cells: Part II—Advanced oxygen electrodes [J]. Applied Catalysis B: Environmental, 2016, 182: 123-131

[13] TianB, LiY-l, LiuY-y, et al.. Ordered membrane electrode assembly with drastically enhanced proton and mass transport for proton exchange membrane water electrolysis [J]. Nano Letters, 2023, 23(14): 6474-6481

[14] MoJ-k, YangG-q, LiY-f, et al.. Experimental studies on the effects of sheet resistance and wettability of catalyst layer on electro-catalytic activities for oxygen evolution reaction in proton exchange membrane electrolysis cells [J]. International Journal of Hydrogen Energy, 2020, 45(51): 26595-26603

[15] DingL, WangW-t, XieZ-q, et al.. Highly porous iridium thin electrodes with low loading and improved reaction kinetics for hydrogen generation in PEM electrolyzer cells [J]. ACS Applied Materials & Interfaces, 2023, 15(20): 24284-24295

[16] LvH, WangS, SunY-w, et al.. Anode catalyst layer with hierarchical pore size distribution for highly efficient proton exchange membrane water electrolysis [J]. Journal of Power Sources, 2023, 564: 232878

[17] QuE-l, HaoX-f, XiaoM, et al.. Proton exchange membranes for high temperature proton exchange membrane fuel cells: Challenges and perspectives [J]. Journal of Power Sources, 2022, 533: 231386

[18] LimJ, ParkD, JeonS S, et al.. Ultrathin IrO₂ nanoneedles for electrochemical water oxidation [J]. Advanced Functional Materials, 2018, 28(4): 1704796

[19] OhnoH, NoharaS, KakinumaK, et al.. Effect of electronic conductivities of iridium oxide/doped SnO₂ oxygen-evolving catalysts on the polarization properties in proton exchange membrane water electrolysis [J]. Catalysts, 2019, 9(1): 74

[20] GayenP, LiuX-q, HeC, et al.. Bidirectional energy & fuel production using RTO-supported-Pt-IrO₂ loaded fixed polarity unitized regenerative fuel cells [J]. Sustainable Energy & Fuels, 2021, 5(10): 2734-2746

[21] SuermannM, SchmidtT J, BüchiF N. Investigation of mass transport losses in polymer electrolyte electrolysis cells [J]. ECS Transactions, 2015, 69(17): 1141

[22] LeeJ K, LeeC, FahyK F, et al.. Accelerating bubble detachment in porous transport layers with patterned throughpores [J]. ACS Applied Energy Materials, 2020, 3(10): 9676-9684

[23] XuW, ScottK. The effects of ionomer content on PEM water electrolyser membrane electrode assembly performance [J]. International Journal of Hydrogen Energy, 2010, 35(21): 12029-12037

[24] ZhouZ-l, YangD-z, GuoY-q, et al.. Effect of the physical adsorption of ionomer on Pt particles on the fluid characteristics of PEMFC catalyst ink [J]. International Journal of Hydrogen Energy, 2023, 48(1): 318-326

[25] OttS, OrfanidiA, SchmiesH, et al.. Ionomer distribution control in porous carbon-supported catalyst layers for high-power and low Pt-loaded proton exchange membrane fuel cells [J]. Nature Materials, 2020, 19(1): 77-85

[26] KodamaK, MotobayashiK, ShinoharaA, et al.. Effect of the side-chain structure of perfluoro-sulfonic acid ionomers on the oxygen reduction reaction on the surface of Pt [J]. ACS Catalysis, 2018, 8(1): 694-700

[27] ChenF-d, ChenS-g, WangA-x, et al.. Blocking the sulfonate group in Nafion to unlock platinum’s activity in membrane electrode assemblies [J]. Nature Catalysis, 2023, 6: 392-401

[28] LiuS-c, LinR, LuJ-p, et al.. The impact of different side chain ionomer on membrane electrode assembly performance and durability [J]. Chemical Engineering Journal, 2023, 472: 145050

[29] ParkY C, KakinumaK, UchidaH, et al.. Effects of short-side-chain perfluorosulfonic acid ionomers as binders on the performance of low Pt loading fuel cell cathodes [J]. Journal of Power Sources, 2015, 275: 384-391

[30] RamaswamyN, KumaraguruS, KoestnerR, et al.. Editors’ choice: Ionomer side chain length and equivalent weight impact on high current density transport resistances in PEMFC cathodes [J]. Journal of the Electrochemical Society, 2021, 168(2): 024518

[31] RenH, TengY, MengX-c, et al.. Ionomer network of catalyst layers for proton exchange membrane fuel cell [J]. Journal of Power Sources, 2021, 506: 230186

[32] KuoA T, TakeuchiK, TanakaA, et al.. Exploring the effect of pendent side chain length on the structural and mechanical properties of hydrated perfluorosulfonic acid polymer membranes by molecular dynamics simulation [J]. Polymer, 2018, 146: 53-62

[33] SubiantoS, CavaliereS, JonesD J, et al.. Effect of side-chain length on the electrospinning of perfluorosulfonic acid ionomers [J]. Journal of Polymer Science A: Polymer Chemistry, 2013, 51(1): 118-128

[34] NiuW-h, YangY. Graphitic carbon nitride for electrochemical energy conversion and storage [J]. ACS Energy Letters, 2018, 3(11): 2796-2815

[35] BanerjeeT, PodjaskiF, KrögerJ, et al.. Polymer photocatalysts for solar-to-chemical energy conversion [J]. Nature Reviews Materials, 2021, 6: 168-190

[36] ZhangW-y, YaoQ-s, JiangG-p, et al.. Molecular trapping strategy to stabilize subnanometric Pt clusters for highly active electrocatalysis [J]. ACS Catalysis, 2019, 9(12): 11603-11613

[37] WuM, GongY-s, NieT, et al.. Template-free synthesis of nanocage-like g-C₃N₄ with high surface area and nitrogen defects for enhanced photocatalytic H₂ activity [J]. Journal of Materials Chemistry A, 2019, 7(10): 5324-5332

[38] YangD-z, GuoY-q, TangH-f, et al.. Influence of the dispersion state of ionomer on the dispersion of catalyst ink and the construction of catalyst layer [J]. International Journal of Hydrogen Energy, 2021, 46(66): 33300-33313

[39] GongQ, LiC-z, LiuY-d, et al.. Effects of ink formulation on construction of catalyst layers for high-performance polymer electrolyte membrane fuel cells [J]. ACS Applied Materials & Interfaces, 2021, 13(31): 37004-37013

[40] HongZ-h, ShenB, ChenY-l, et al.. Enhancement of photocatalytic H₂ evolution over nitrogen-deficient graphitic carbon nitride [J]. Journal of Materials Chemistry A, 2013, 1(38): 11754-11761

[41] MandalM, MooreM, SecanellM. Measurement of the protonic and electronic conductivities of PEM water electrolyzer electrodes [J]. ACS Applied Materials & Interfaces, 2020, 12(44): 49549-49562

[42] LvC-d, QianY-m, YanC-s, et al.. Defect engineering metal-free polymeric carbon nitride electrocatalyst for effective nitrogen fixation under ambient conditions [J]. Angewandte Chemie International Edition, 2018, 57(32): 10246-10250

[43] PapakonstantinouG, Algara-SillerG, TeschnerD, et al.. Degradation study of a proton exchange membrane water electrolyzer under dynamic operation conditions [J]. Applied Energy, 2020, 280: 115911

[44] PomillaF R, CortesM A L R M, HamiltonJ W J, et al.. An investigation into the stability of graphitic C₃N₄ as a photocatalyst for CO₂ reduction [J]. The Journal of Physical Chemistry C, 2018, 122(50): 28727-28738

[45] SunW, LiuJ-y, GongX-q, et al.. OER activity manipulated by IrO₆ coordination geometry: An insight from pyrochlore iridates [J]. Scientific Reports, 2016, 6: 38429

[46] KimB J, JinH, MoonS J, et al.. Novel J _eff=1/2 Mott state induced by relativistic spin-orbit coupling in Sr₂IrO₄ [J]. Physical Review Letters, 2008, 101(7): 076402

RIGHTS & PERMISSIONS

Central South University