o3 Deep Research main response (part 3 of 3)
7. Producing 12 Matched Electrodes for Academic Trials
When producing a larger batch (e.g. 12 electrodes) for multi-lab trials or comparative experiments, the process must be highly repeatable so that all electrodes are as identical as possible. Below is a detailed, repeatable method for plating 12 titanium rod electrodes in one run or in consistent sub-batches:
7.1. Batch Preparation:
Material Prep: Obtain 12 titanium rods from the same source lot if possible to ensure identical composition and surface condition. Number or mark each rod (e.g. 1–12) on the unplated end for tracking.
Follow Surface Prep (Section 5) meticulously for each rod: It’s best to process all rods together in each step to maintain consistency. For instance, degrease all 12, then etch all 12 in one acid bath (using a holder or doing a few at a time in quick succession). Use fresh cleaning solutions as needed (don’t let one rod’s dirt redeposit on another). If using HF etch, you can dip multiple rods at once using a Teflon rack or by holding several with PTFE string—just ensure equal exposure time (Titanium platinum plating question | Gold Refining & Metal Extraction Forum).
Setup Plating Bath: Use a plating vessel large enough to accommodate all 12 rods at once or be prepared to plate in smaller batches (e.g. 3–4 at a time) with identical conditions. Plating all 12 simultaneously is ideal for uniformity, but requires a bit more setup:
- Arrange an inert anode (or multiple anodes) so that each cathode (Ti rod) “sees” a similar anode-to-cathode distance. For example, you can use a platinized titanium mesh sheet bent into a cylindrical shape surrounding the rods, or a pair of mesh strips on either side of a row of rods, to provide even current distribution.
- Mount the 12 rods on a non-conductive rack or holder. Ensure they are parallel, separated (no touching each other), and all dipped to the same depth (35 mm). A possibility: drill 6 mm holes in a plastic bar as a holder, or 3D-print a jig, to hold rods in place.
- Connect all rods electrically together to the power supply’s negative output. This can be done by clamping all their unplated ends with a single bus bar or using wires that join to a common node (make sure the contact resistance to each rod is low and similar – tighten screws or clips firmly).
- Essentially, you create a “cathode tree” of 12 identical parts.
Solution Volume: Use a sufficient volume of plating solution so that the total platinum in solution can plate all rods without significant depletion. For 12 rods at ~0.035 g Pt each (for ~2.5 µm), that’s ~0.42 g Pt total. If your solution has 4 g/L, use at least 0.5 L (which has ~2 g Pt) so that even after plating, plenty of Pt remains in solution (and the concentration drop is at most 20%). This ensures plating rate doesn’t slow toward the end and all rods get the same environment. Alternatively, if using a smaller volume, you may need to replenish the solution with concentrate after a certain number of rods – but in one simultaneous batch, that’s not possible, so better to use a sufficiently sized bath initially.
7.2. Plating Process (for batch):
Constant Current Plating: For best uniformity, use a constant current source and divide the current among the 12 rods. First, calculate the total area to be plated: one rod ~6.59 cm² (side) + ~0.28 cm² (tip) ≈ 6.87 cm². Twelve rods ~82.5 cm² total. Decide on a current density (say 10 mA/cm² as a moderate value). That would require ~0.825 A total current for 82.5 cm². Set the power supply to current-control mode at 0.825 A. If your supply can’t output that high, use a lower current density (5 mA/cm² → 0.412 A total). Make sure the anode area is ample so it can supply this current without polarization issues (platinum mesh has high capacity).
Begin Plating: With rods immersed and all connections double-checked, turn on the current. Bubbles (hydrogen at cathodes) will evolve; gentle agitation helps dislodge them so they don’t cause bare spots. You can manually stir the solution or use a magnetic stir bar. Ensure all rods are bubbling similarly – this is a visual cue that current is distributed evenly.
Time Control: Plate for the calculated time to reach desired thickness. Using Faraday’s law: the charge (Q) needed = area × thickness × density × (F/z/M) basically, but easier is to use the known plating efficiency if given. Many platinum baths have ~>90% cathode efficiency. For simplicity, one can empirically time based on earlier single tests or weight targets. For example, if one rod needed 15 minutes at 10 mA/cm² to get ~2.5 µm, then 12 rods at same current density also need ~15 minutes (since each cm² gets the same current density, the plating rate per area is the same). Monitor the process but avoid stopping midway (an interruption can sometimes cause oxidation or slight variation unless handled carefully).
Rotation (if needed): If you suspect slight unevenness (rods closer to an anode plate might get more current), you can rotate the rod holders halfway through plating to even it out – but if the anode setup is symmetric, this shouldn’t be necessary.
Completion: Once the time or charge is reached, turn off the current. Do not over-plate excessively as very thick deposits can introduce stress. Remove the rods from the bath promptly.
Rinsing: Immediately rinse all plated rods in a large volume of distilled water. This removes residual acidic solution and prevents any chemical attack or staining. Then rinse in deionized water. Handle rods gently; though platinum is deposited, it’s best not to knock them together to avoid any potential mechanical damage when freshly plated.
Post-Treatment: Some platers recommend a post-plating heat treatment for adhesion (e.g. annealing in hydrogen at ~700 °C as mentioned in literature for Pt/Ti) (Titanium platinum plating question | Gold Refining & Metal Extraction Forum) (Titanium platinum plating question | Gold Refining & Metal Extraction Forum). However, this is usually not feasible in most labs and likely unnecessary if prep and plating were done well. Our electrodes should have good adhesion as-is. You may simply dry the rods (air dry or gentle blow dry). If any plating solution components tend to stain, a dip in very dilute nitric acid can neutralize residues (though with modern platinum baths this isn’t usually an issue).
7.3. Ensuring Reproducibility:
Characterize one or two rods: Take weight measurements of a couple of rods to ensure thickness met the target (Section 6). If the result is slightly off, you can adjust plating time for the next batch.
Uniformity Check: All 12 should look identical. Compare their appearance and weight. If one rod appears different, you may have had a contact issue on that rod – this needs addressing before the next run.
Document the Process: Write down the exact parameters used: solution type and volume, current (or voltage) and time, temperature, agitation method. This recipe should be followed by other labs. Encourage each lab to replicate these conditions as closely as possible. For instance: “Plated 12 electrodes simultaneously at 5 mA/cm² for 30 min at ~25 °C in 500 mL of Spa Plating solution, using a Pt mesh anode encircling the cathodes.” Such details help others match your process.
Batching vs Sequential: If a lab lacks the ability to do all 12 at once (maybe their power supply can’t source enough current or they only have a small beaker), it’s acceptable to plate in two or three batches. In that case, it’s vital to keep conditions constant:
- Use the same solution (or same volume replenished to original concentration) for each batch.
- Plate each batch for the same time and current density.
- Perhaps swap the order of rods (don’t always put the same subset in the first batch) in case there’s slight solution depletion over batches.
But ideally, design the plating setup so even small labs can do one batch. For example, plating 6 at a time (two batches) is workable – still, all 6 in a batch should be uniform, and you’d compare batch1 vs batch2 by weight to ensure consistency.
7.4. Cross-Lab Consistency:
Once Lab A produces 12 electrodes, Lab B in another location should attempt the same protocol. They should compare notes: e.g., weights of their electrodes, visual appearance, any differences. Minor discrepancies can be ironed out (maybe Lab B’s power supply was uncalibrated, giving slightly lower current – they might increase plating time by 2 min to compensate).
It might be wise for one lab to send a couple of electrodes to another as references. Alternatively, all labs send one electrode to a central facility for thickness measurement (via XRF or SEM). This external validation can certify that “all labs achieved ~2.5 µm ±0.2 µm plating” – boosting confidence in experimental data obtained with those electrodes.
In the AMYBO context, the community’s collaboration (as seen with sharing designs and Spa Plating’s input (Evaluating platinized electrodes for electrolysis - Development - AMYBO.org)) is valuable. If one lab perfects the plating procedure, they should share any tips or slight modifications needed. Over a few iterations, a robust standard operating procedure (SOP) for making 12 matched electrodes will emerge.
By following the above method, you can reliably produce a dozen platinum-plated Ti electrodes that are virtually identical. These can then be distributed to different research groups, used in parallel experiments, or kept as spares – all with confidence that each electrode is equivalently manufactured. This level of consistency is crucial for academic trials comparing results across different locations.
8. Producing 2 Matched Electrodes Using an ElectroPioreactor
For small-scale needs – say you want to make just a pair of electrodes for a pilot experiment or to test the feasibility – you might consider using the ElectroPioreactor itself as a mini-plating setup to save cost. This section outlines a cost-effective methodology for plating a pair of electrodes and assesses using the electroPioreactor versus a bench supply in this scenario.
8.1. Setup for 1–2 Electrodes in the ElectroPioreactor:
Using the Pioreactor Vessel: Leverage the 20 mL vial and cap designed for electrolysis. The community has a vial cap design with a hole for a 6 mm electrode (Evaluating platinized electrodes for electrolysis - Development - AMYBO.org), which is perfect for holding your titanium rod. Print or obtain this cap, and mount the titanium rod (to be plated) through it so that ~35 mm extends into the vial. For the counter electrode, you can use a small platinized titanium mesh or the second titanium rod (though if the second rod is also to be plated, you’d have to configure a way to plate one as cathode and use another as temporary anode, then swap).
Wiring: Connect the rod to the Pioreactor’s LED driver channel (for instance, channel D positive to the rod for cathode, and channel D negative to the counter electrode if the Pioreactor is sourcing current in that configuration as it did for electrolysis (Evaluating platinized electrodes for electrolysis - Development - AMYBO.org) – note, previously they connected platinized electrode to positive and SS to negative to generate hydrogen (Evaluating platinized electrodes for electrolysis - Development - AMYBO.org); for plating, the titanium rod must be the cathode (negative) so it receives platinum). You may need to invert connections: titanium rod on negative, platinum mesh on positive of channel D.
Plating Solution in Vial: Fill the vial with a small volume of platinum plating solution. 20 mL might be sufficient for a thin plating on one rod. Since volume is small, platinum concentration will deplete faster – consider using the highest concentration solution available or replenishing after one electrode. Alternatively, if you can get a slightly larger container (maybe a 50 mL tube) that still fits in the Pioreactor heater/stir base, that could allow ~30–40 mL solution.
Parameters: Set the Pioreactor to drive current. For example, start with a low LED intensity (e.g. 10–20%) as per the earlier electrolysis tests (Evaluating platinized electrodes for electrolysis - Development - AMYBO.org). You might need to determine empirically what current that corresponds to. One approach: connect a multimeter (in series or use a shunt resistor) to measure the actual current at a given setting (e.g. 10% gave X mA). Suppose 10% intensity yields ~10 mA through the electrode pair – that might be ~1.5 mA/cm² for a 6.59 cm² area (very low). You may increase intensity to max (100%) if needed. If 100% corresponds to, say, 50 mA (this is hypothetical), that would be ~7.6 mA/cm² – which might plate slowly but at least reasonably.
Plating Procedure with Pioreactor:
- Clean and etch the titanium rod as in Section 5 (do this outside the Pioreactor).
- Insert it into the cap/vial with plating solution. Insert the anode (mesh) as well – maybe attach it to another port on the cap or dangle it in solution without touching the Ti rod.
- Start the current via Pioreactor software. Let it run for an extended time – possibly several hours. Monitor occasionally for any signs of problems (excessive bubbling, which could raise pH or cause non-uniformity in such a tiny volume – if so, you might dial down the intensity intermittently).
- After the time, stop and rinse the rod.
Swap and Repeat: Plate the second rod in the same manner. (If you used the second rod as an anode initially, that rod will not really receive Pt – it might get slight oxidation. Clean it and then plate it as cathode with the first rod or mesh as anode.) Because conditions in the Pioreactor are limited, try to ensure the total charge passed (current × time) is the same for both rods. For instance, if you ran 10 mA for 4 hours (~144 C of charge) for rod 1, do the same for rod 2. This should give comparable thickness.
8.2. Bench Supply vs. Pioreactor for 2 Electrodes:
Feasibility: It is feasible to use the Pioreactor alone, as demonstrated by the team’s electrolysis experiments. The Pioreactor effectively acted as a low-current power source (Evaluating platinized electrodes for electrolysis - Development - AMYBO.org). For plating 2 small electrodes, this can work – albeit slowly. The advantage is cost: you avoid buying a bench supply, using the hardware you already have.
Drawbacks to consider:
- Time: Plating could take a long time due to low current. If the Pioreactor can only supply, say, 10 mA, depositing 0.035 g Pt might take on the order of tens of hours (depending on efficiency). This ties up the device and requires patience.
- Monitoring: The Pioreactor’s software isn’t built to measure plating current or automatically stop at a certain point, so you have to approximate or manually time it.
- Solution Volume: 20 mL is a very small bath. The local platinum ion concentration near the cathode may drop during plating, risking a rough or non-uniform coat. Agitation is limited in the tiny vial (though bubble stirring from gas evolution might help a bit). If possible, stirring with a small magnetic flea in the vial (if the Pioreactor has a stirrer) or manually swirling occasionally will improve uniformity.
- Quality: There is some risk the deposit might be less adherent or uniform compared to a proper setup. However, if all you need is a functional platinized surface and you’re willing to potentially re-plate or accept a slightly thinner coating, this method can be acceptable.
Bench Power (even for 2 electrodes): If a bench supply is available (or can be borrowed), you could still use the Pioreactor vial as the container, but drive the plating with the bench supply. This hybrid approach might be best:
- You’d still benefit from the small volume (less solution used) and convenient electrode holding of the Pioreactor setup, but get more control with the supply. For instance, set 20 mA on the bench supply and plate for a calculated time to get ~2 µm.
- This way, you reduce plating time and have a clearer idea of the deposition. The Pioreactor itself can be turned off or just used to hold the vial (ensuring the Raspberry Pi isn’t sourcing the current).
- Using the bench supply also avoids any chance of damaging the Pioreactor electronics if something draws more current than expected.
Cost Analysis: If truly avoiding extra cost is crucial, the Pioreactor-only method saves ~£60–£100 (cost of a PSU). All other materials (plating solution, etc.) you’d need regardless. But consider the value of your time: a bench supply might plate an electrode in 30 minutes that would otherwise take 5+ hours on the Pioreactor. For two electrodes, maybe that’s manageable; for larger numbers it’s not. If many labs are going to do this, likely at least one bench supply per lab is a good investment (often labs have one already for general use).
8.3. Procedure Recap for 2 Electrodes (Pioreactor method):
- Clean/etch both rods (maybe etch them together in the same bath).
- First rod plating: Setup in Pioreactor vial with Pt solution and inert anode. Run Pioreactor channel at highest safe setting for a fixed time (record this).
- Second rod plating: Repeat with identical setting/time.
- Rinse and test both rods. They should have a visible Pt coating. Perform a simple check (weight or appearance). If one looks thinner, you might give it another session in the plating bath (with fresh solution if the first run exhausted it).
8.4. Outcome and Use:
- The two electrodes produced should be comparable to each other. They might have a slightly thinner platinum layer than the “ideal” 2.5 µm if time/current were limited. If they function well in initial tests (e.g. they produce no discoloration and remain stable during electrolysis, like the short platinum electrode in the forum test which maintained clear solution (Evaluating platinized electrodes for electrolysis - Development - AMYBO.org) (Evaluating platinized electrodes for electrolysis - Development - AMYBO.org)), then the method is a success.
- If problems are encountered (e.g. plating flakes off), you may need to resort to a bench supply or improve surface prep. Often, inadequate current can cause poor adhesion because the initial nucleation (“strike”) might not have been strong – one trick is to give a very short burst at a higher current (if possible) at the start to help nucleate Pt, then lower it. The Pioreactor might not allow a “burst” easily unless you manually swap to a bench supply briefly for a strike.
8.5. Conclusion on Small-Scale Method:
Using the ElectroPioreactor to plate a couple of electrodes is feasible and cost-effective, but it comes with trade-offs in time and possibly plating quality. It’s a clever use of existing equipment for a one-off or pilot run. However, for reproducibility across labs, if each lab tries to do this with their Pioreactor, slight differences in how the Pioreactor outputs current could introduce variability. Therefore:
- If the goal is absolute consistency across the world, it might still be better for each lab to use a standard power supply method.
- If the goal is to enable even resource-limited labs to create functional electrodes, then the Pioreactor method is valuable – just advise them on careful execution.
In summary, for two matched electrodes, one can successfully use the ElectroPioreactor as a micro-plating setup, but must be attentive to detail and possibly accept a longer process. Whenever possible, verify the end results (by weight or performance) to ensure those two electrodes meet the criteria. This approach underscores the flexibility of the Pioreactor system but also highlights why dedicated plating hardware is recommended for larger-scale standardization efforts.
References:
(Evaluating platinized electrodes for electrolysis - Development - AMYBO.org), (Evaluating platinized electrodes for electrolysis - Development - AMYBO.org) – Gerrit’s experiment setup with Pioreactor for electrolysis (indicates Pioreactor channel usage).
(Evaluating platinized electrodes for electrolysis - Development - AMYBO.org) – Observation of cheap platinized electrode failing (importance of quality plating).
(Evaluating platinized electrodes for electrolysis - Development - AMYBO.org) – Martin suggesting electroplating titanium bolt anodes (need for plating process).
(Evaluating platinized electrodes for electrolysis - Development - AMYBO.org) – Spa Plating’s Richard providing custom electrodes and videos (expert endorsement of DIY plating).
(Microsoft Word - Surface World Article - Web Copy 27.03.07.doc) – Typical platinum thickness ~2.5 µm on titanium anodes.
(P52510 | Platinum Plating Solution) – Example platinum plating solution specs (4 g Pt/L, 0.2–20 µm range, high uniformity).
(Titanium platinum plating question | Gold Refining & Metal Extraction Forum) – Expert advice on titanium activation: detergent, HF or alternatives (ammonium bifluoride + sulfuric) to enable plating.
(Bench Power Supply - Amazon.co.uk) – Example bench power supply on Amazon (~£60, widely used).
(72-2540 - Single Output DC Bench Power Supply with RS232 … - CPC) – Example bench power supply spec/price from Farnell (~£89).
(Titanium, rod, 100mm, diameter | GF04311638-1EA) – Titanium rod 6 mm spec (Grade 2, 99.6% pure).
(uxcell 5Pcs GR5 Titanium Rod, Dia 6mm 0.23" Length 100mm 3.94 …) – Availability of small GR5 titanium rods pack (for DIY).
(How to Estimate Gold Content in Gold Plated Parts - A.G. Metals) – Formula linking surface area, thickness, density to plating mass (used for thickness calc).
(Plating Thickness Measurements - Applied Technical Services) – XRF is a nondestructive method for measuring coating thickness (suitable for Pt on Ti).
ENDS