Raney-nickel alloy electrodes for alkaline water electrolysis. Asif Ansar. German Aerospace Center

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1 Raney-nickel alloy electrodes for alkaline water electrolysis Asif Ansar German Aerospace Center

2 Regine Reissner, Daniela Aguiar, Taikai Liu, Günter Schiller - Light House Project Power-to-Gas ZSW (DE) Andreas Brinner - RESelyer DTU (DK) Jake Bowen - Bilateral collaboration FZJ (DE) Marcelo Carmo

3 Projekt HYSOLAR Hydrogen from solar energy 1980 / 90 s: German Saudi-Arabia Joint Project on Hydrogen Production with AWE coupled with Photovoltaic R&D AWE demonstrators: 350 kw in Riyadh, 10 kw in Stuttgart System efficiency: 5.2 %, Efficiency PV: 8.1 %, Efficiency AWE: 80.0 %

4 Electrolyser Systems and Test stations P = 2 350/500kW, p = 1-10bar abs, T = C HT HT/DLR HT/ DLR OEM supplier: HYDROGEN SYSTEMS / METKON ALYZER 10kW OEM supplier: HYDROTECHNIK 3 / 2 kw HS HS/DLR FZJ MA OEM supplier: FZ JÜLICH 10 kw FZJ/DLR MA/DLR FZJ/DLR

5 Hydrogen Production Today - 4% from electrolysis Source: DoW chemic. Nature gas: US$8.5/GJ Coal: US$6.3/GJ Biomass: US$14.2/GJ Datasource: PSI, Switzerland AWE: US$19.9/GJ Wind+AWE: US$11.4/GJ 1GJ m 3 H Kg H2 at 1 bar at 25 C

6 Targets Performance: Operate at 1.2 A cm 2 with a cell potential of 1.8 V Source: %20Electrolysis%20Status%20and%20Potential%20fo r%20development.pdf Durability: hours with on-off cycles with less than 10% degradation Cost: Reduce by 30% at stack level

7 Ligh House Power to Gas Project Pressurized Alkaline Electrolyzer of ZSW

8 Block Diagram and System Interfaces of the R&D Electrolysis Plant

9 Advanced Alkaline Electolysis Stack of ZSW (300kW-Stack for Pressurized Plant Operation) - 9 -

10 3000 cm 2 Electrode Packages (Eff. area 2750 cm 2 ) for Pressurized Alkaline Electrolyzers Bipolar plate Perforated Sheet as a Working Electrode on both sides of the Bipolar Plate - Anode - Cathode Nominal Current Density: 1 A/cm 2

11 Catalysts for AWE Bodner et al., WIREs Energy Environ 2014, doi: /wene.150

12 Benchmarked Catalyst for AWE HER NiAl (54:46 wt%) alloy NiAlMo (52:38:10 wt%) alloy OER NiAl (54:46 wt%) alloy NiAl + Co 3 O 4

13 Electrodes Fabrication Vacuum Plasma Spraying (VPS) Principle of Plasma Spraying Plasma Gases Ar H 2 N 2 He Particle Injection Coating as-sprayed activated

14 Electrode Performance Half Cell Test Configuration Hafl cell measurement Electrode area: 4 cm 2 ; Cathode: NiAlMo / Anode: NiAl; Conditions: 70 C, 30 wt.% KOH

15 Electrode Performance Full Cell Test 2.4 mm 0.5 mm Zirfon layer 1 Internal electrolyte by-pass Zirfon layer 2 Double side coated PPS spacer-fabric, Zirfon (ZrO 2 /polymer composite) dual layer Variation of permeability of Zirfon layers: from 120 l/(h m 2 bar) to 900 l/(h m 2 bar) Separators of 300 cm 2 delivered for cell and stack integration Technical scale (2500 cm 2 ) producibility demonstrated

16 Electrode Performance Full Cell Test with Alternative diaphrams/membranes

17 Electrode Performance Durability Overpotential Cathode / V -0,1-0,2-0,3-0,4-0,5-0,6-0,7 NiAlMo coated electrode long term test; original and IRcorrected voltage at 0.5 A/cm On-off operation OCV Coated electrode U measured coated electrode U IRcorrected On-off operation OCV RES-Ni228 days

18 Electrode Fabrication by Air Plasma Spraying APS normal (Single electrode plasma gun) VPS APS (normal) APS Triplex (Three electrode plasma gun) APS (Triplex)

19 APS Electrodes Performance Half Cell Configuration

20 APS Electrodes Performance Half Cell Configuration normal

21 APS Electrodes Performance Half Cell Configuration normal

22 APS Electrodes Performance Half Cell Configuration NiAlMo coating cross section after spraying with APS-Triplex with different particle velocity and activation Plasma in-flight particle velocity

23 Electrochemical Characterization of APS-Anodes NiAl/NiAl+Co 3 O 4 Process: APS Triplex Catalyst: NiAl + Co 3 O 4

24 APS vs VPS Electrodes Cost VPS APS Yield per day 3 m² 3 m² CAPEX 2,8 million 0,480 million Depreciation time 10 years 10 years Machine cost per day Other operating costs per day Machine + other operating cost per m² Staff cost per day Coating cost per m² Cost reduction from VPS to APS can be above 50% and as much as 72%

25 Electrodes Structure

26 Electrodes Structure - Raney-Ni/NiMo electrodes (Vacuum Plasma Spray - VPS) TEM Before in-situ operation - High surface area - BET: 40 m 2 /g - Presence of nano dendrides

27 Electrodes Structure Highly heterogeneous microstructure with many subdomains. Dendritic structures stemming from the dissolution of Al from the Raney type NiAl alloy particles. Desert rose like nano flake structures (Ni(OH) 2 ) observed in the pores especially after long term operation

28 Electrodes Structure Influence on performance is still open question

29 Electrodes Structure - Raney-Ni/NiMo electrodes (Vacuum Plasma Spray - VPS)

30 Electrodes Structure - Loss of Surface Area after in-situ operation Transmission Electron Microscopy TEM Anode Side Oxygen Evolution Before in-situ operation - High surface area - BET: 40 m 2 /g - Presence os nano dendrides After in-situ operation - Low surface area - BET: < 4 m 2 /g - Nano-dendrides are gone! TEM Analysis very challenging due to the high NiO concentration

31 Electrodes Structure - XPS data indicating CoO formation in APS anodes

32 Compact AWE - More than 35% of the surface of electrodes is empty Philipp Lettenmeier et al, Abstarct 39 Tuesday 13/6 at 17:00

33 Thank you Asif Ansar German Aerospace Center (DLR)