low-cost and durable bipolar plates for proton exchange membrane electrolyzers

by:Petolar     2020-10-11
Cost reduction and efficiency improvement are the main challenges in the sustainable H2 production of proton exchange membranes (PEM)electrolysis. Titanium-
Basic components such as bipolar plates (BPP)
The greatest contribution to capital costs.
This work proposes the use of stainless steel BPPs for the coating of Nb and Ti by RF sputtering physical vapor deposition (PVD)
Vacuum plasma spraying (VPS), respectively.
Physical properties of the coating by scanning electron, atomic force microscope (SEM, AFM); and X-
Ray diffraction, photoelectric spectrum (XRD, XPS).
Ti coating (50u2009μm)
Protect stainless steel substrates from corrosion while 50-
The fold thin layer of Nb reduces the contact resistance by nearly an order of magnitude. The Nb/Ti-
Coated stainless steel bipolar BPPs withstand harsh environments where the anode exceeds 1000 km/h under nominal conditions, showing presence in large-
Large-scale production of H2 using renewable energy.
Anti-corrosion coating of Ti deposited by vacuum plasma spraying (VPS)
As reported elsewhere
Subsequently, the surface modification of Ti and Nb (Nb/Ti)
Physical Vapor Deposition (PVD).
Before the Nb coating is deposited, the Ti coating is polished with different grades of SiC and no abrasive agent is used until a smooth surface is obtained with SC4000 sandpaper.
The same process is used for reference stainless steel substrates.
Metal Nb coatings are deposited by RF sputtering process using industrial-sized gases
Flow auxiliary coating machine (
Wan, SYSTEC Co. SVS, Germany)
, Can accommodate 4 targets of 100 u2009 × 200200, able to deposit complex compounds.
Before coating with Nb, etching the substrate with ar plasma by reverse sputtering using a 500 v pulse bias voltage for 20 minutes.
The Nb layer is then deposited by applying a power of 1.
0kw kw, lasting 15 minutes, gets a layer thickness of 1. 4u2009μm.
20 cm active BPP was deposited by the coating (
The stacking model 92E of 92ics).
BPP has a complex flow field design, which is the proprietary information of hydrogen and cannot be disclosed. Cross-
Cross-Section anti-scattering electrons (BSE)
Micrographs were recorded with Zeiss superelectron microscopy with an acceleration voltage of 15 kv.
The images are recorded before and after the corrosion test described below.
Multi-Mode 8 AFM with Bruker (
Carlsruea, Germany).
The AFM is equipped with x-
Y closed loop scanner with open loop z-axis (nPoint, USA)
For Peakforce tapping.
The sample is fixed on a 12mm steel plate with silver glue.
For current recording and current-
Voltage curve measurement, Peakforce tuna amplifier and PtIr-
A coated AFM probe is used (PPP-NCHPT, 42u2009N/m; Nanosensors).
For all current measurements, apply a voltage of 3 µV between the scanner/sample and the AFM tip.
A bearing analysis with a threshold of 20 pa is used to evaluate the area of the relative conductive sample. The i(v)
The curve is increased from-2 v to 2 v.
For energy gap determination, the threshold value of 1 cucna is used.
Measurements were made at room temperature and relative humidity of 20%.
In Peakforce-, the roughness is measured with multi-mode 8 afm
Hit mode by evaluating 10 × 10 μm images of Ti/ss, Nb/ss and Nb/Ti/ss.
Determination of surface roughness parameters: Arithmetic mean value (R)
And the root square (R)
In these layers, 21 sub-regions of each measured image were selected, with a size of 1 × 1 μm.
Based on the depth profile recorded using AFM, the roughness of Nb coated samples is calculated to achieve the arithmetic mean value of the absolute value R. The X-
Measured by X-ray diffraction
X-ray diffraction diffractometer found v. tecntec-from Brook-bound area detector-
2000 under Prague reflection modeBrentano-conditions. The X-
The Ray is emitted from a copper anode with an acceleration voltage of 45 kv and a pipe current of 0,650.
The diameter of the straightener is 1mm.
4 frames were completed and the integration time per frame was 80 kbps s.
The starting position is 12 ° (2-Theta)
Until the straightener-angle of 46. 5° (in 4 steps)was reached.
XPS experiments were performed at room temperature in Thermal Science ESCALAB 250 ultra
High vacuum facility with base pressure of 1 × 10 mbar. The Ar-
The depth distribution of sputtering was carried out with a hot EX05 ion gun.
The Ar sub-pressure is set to 2-3 u2009 × 10 mbar, generating 3-7 in an area of 3 × 4mm at 2 kv acceleration voltage and 10 ma emission current
XPS measurements of Al k α X-ray source (Thermo XR4)
Lens mode covering 0.
The surface area of 8mm was selected.
No calibration of the sputtering output.
Therefore, the sputtering depth is provided at Ar ion dose.
Detailed spectra of C1s, O1s, Ti2p and Nb3d were recorded in each experiment.
In addition, the measured spectra were recorded in the binding energy range 0-1000 ev before and after the final sputtering step.
In order to obtain in-depth information on resistance behavior associated with compaction pressure, contact resistance measurements were carried out.
Virtual samples of Ti/ss, Nb/Ti, Nb/ss and Nb/Ti/ss (Coated 1. 8 to 1. 8u2009cm)
Placed between two Cu cylinders that were polished until the mirror was polished before.
Unprocessed Toray paper (280u2009μm thick)
No porous layer (MPL)
It is used as a compressed contact element for the measurement of the CRS.
Toray paper is placed between the coating and the Cu surface. The sandwich-
Just like compression arrangement with hydraulic press.
The measurement is carried out by applying a DC current of 5 u2009 a by a constant potential meter (
Zahner elektrik IM6)and booster (Module PP240).
The force applied varies from about.
Month to 650 ÷ N cm.
The ICRs of the coating are calculated according to the Circuit of the series resistance, which corresponds to the contact interface.
The Ohm drop caused by the copper/carbon interface is determined by using only carbon paper without any coating samples.
Both the original plate and the bipolar plate were also measured by the ICR.
More details are given about the measurement of the CRS.
Corrosion was measured in half a month.
Battery using the electrode sample holder, of which 1. 8u2009×u20091.
A square sample of 8 cm size was installed to expose the active area of 1 cm to 0.
5 m HSO electrolyte solution. A three-
The electrode assembly includes the above working electrode, Pt disk and reversible hydrogen electrode (RHE, HYDROFLEX)
Used as counter and reference electrode respectively.
The dynamic potential and timing current properties are recorded using a constant potential meter/ammeter (
PGSTAT12)in O-
The anode side conditions of proton exchange membrane electrolysis are simulated in a saturated environment of 65 °c.
Measurement protocols for all samples, namely Nb/Ti, Nb/Ti/ss, Ti/ss and Nb/ss, were established.
It starts with a positive and reverse linear scan KVA (LSV)from −0. 2 to 2u2009V RHE (
Scan rate of 5 kbps mV CUCs)
Clean the surface of the coating.
Again, another scan was performed at 1 mvmv CUCs to determine the corrosion current ()and potential ().
Timing current measurement (6u2009hours)
Tracking was performed at 2 mvv RHE, and finally a dynamic potential measurement was performed at 1 mvmvhe s to determine the change in the electrochemical properties of the sample. The Nb/Ti-
Coated stainless steel bipolar plate assembled in Rainbow 2-120 active area-
Short Stack of community (
92E type (hydrogen).
The coating was evaluated on the anode side of the two batteries.
Both batteries have the same good corrosion protection metal
Based on the current collector on the anode side, the carbon-based gas diffusion layer on the cathode side.
Multilateral Environmental Agreements on commerce (
E400 Green, Ir-
Base anode and Pt-
Base cathode electrode coated on Nafion n1153 cs)
Used in two cells.
The nature of the catalyst is green proprietary information and cannot be disclosed.
Difference between two batteries located on the cathode side: Battery 1: Pt/Ti-
Stainless steel coating; Cell 2: Nb/Ti-
Coated stainless steel, while BPPs for both batteries are coated with Nb/Ti on the anode side.
The stack was tested in a commercial proton exchange membrane electrolytic device (0. 75–2.
Hydrogen Generator, hydrogen).
The unit does not allow the control of operating temperature.
Neither the chimney nor the reservoir has a heating/cooling system.
Depending on the operating current density, the stack reaches a certain temperature.
Initially, the stack was evaluated under a constant 1 aa cm for about a few days. 38u2009°C, and 6.
5x10 pa balance pressure system.
After reaching the activation time of the stable state, the stack is characterized by recording the polarization curve (
Step 4 s of Momma cuccm)
Up to about 1 Cuca cuccm. 28u2009°C.
Similarly, the impedance spectrum (EIS)
At a constant current of 27 ° c, 20 ° c, an amplitude of 3 ° c and a frequency starting from 0.
1 and 750 hz were performed.
The amplitude selection is as low as possible, but high enough to observe the appropriate response.
In this particular case, given the low resistance of the large active surface of the 120 cm battery, choose 3 u2009 a as the amplitude.
1 month after the conditions of the Cuca cuccm 1000 Thanh.
5x10 pa balance pressure and ca.
38 °c repeated measurements under the same operating conditions.
External constant potential meter/galvanostat (
Zahner elektrik IM6)and booster (Module PP240)
Used to perform EIS.
The water quality is constantly controlled and does not reach a resistance below 10 m Ω (0. 1u2009μS). The ion-Exchange Resin (
Aldex chemicalLTD)
Before the stack entrance of the anode side circuit, the analysis was carried out before and after the long run
Determine the term test of the bipolar plate corrosion product.
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