If everything is connected correctly, that is normal. because some gas disolved in the electrolyte and becomes bubbles on the surface close. It will not affect to much. You can change the position of reference to avoid bubbles. for example, putting the reference below the working always works.

yeah it effects on the reading. you should stirr the solution remove the bubbles and take reading again

Bubbles on the reference electrode during the Hydrogen Evolution Reaction (HER) could be caused by various factors related to the reaction environment and the nature of the electrochemical setup. Here are some potential reasons:

1. Hydrogen Diffusion and Overproduction

• Cross-Talk of Hydrogen Gas: If the working electrode produces excessive hydrogen gas, some of it may diffuse or flow toward the reference electrode. This is common in setups with high hydrogen production rates or inadequate separation between electrodes.
• Proximity Effect: In small electrochemical cells or improperly designed setups, hydrogen generated at the working electrode might reach the reference electrode.

2. Electrolyte Contamination

• Impurities in the Electrolyte: Contaminants in the electrolyte might react near the reference electrode, producing gas bubbles. For example, trace amounts of dissolved oxygen can react with hydrogen to form water, releasing small amounts of gas.
• Electrolyte Decomposition: Certain electrolytes can undergo decomposition under HER conditions, releasing gases like oxygen or nitrogen.

3. Reference Electrode Instabilities

• Reference Electrode Reaction: If the reference electrode is not ideally inert (e.g., Ag/AgCl), small reactions might occur at its surface, potentially releasing gas bubbles.
• Dissolved Gases in Electrolyte: If the electrolyte is not degassed properly, dissolved gases like oxygen or nitrogen can form bubbles near the reference electrode due to agitation or supersaturation.

4. Cell Design Issues

• Hydrodynamics: Poor flow management or insufficient mixing in the electrochemical cell can lead to uneven gas distribution, causing bubbles to form at unintended sites, including the reference electrode.
• Insufficient Separation: In systems without proper separation or shielding (e.g., using a Luggin capillary or salt bridge), gases from other electrodes can affect the reference electrode.

5. Experimental Setup Conditions

• High Current Densities: If the HER is conducted at very high current densities, the excessive hydrogen gas production can saturate the electrolyte and lead to bubble formation throughout the cell, including near the reference electrode.
• Poorly Sealed Electrodes: Improper sealing of the reference electrode or an exposed junction could allow gas to accumulate on its surface.

Mitigation Strategies:

If the bubbles persist, carefully evaluate the experimental setup and conditions to identify and address the source of the problem.

Bubbles on the reference electrode during hydrogen evolution reaction (HER) are likely caused by hydrogen gas diffusion from the working electrode to the reference electrode, especially in a poorly sealed electrochemical cell or one with insufficient separation between electrodes. This can alter the reference electrode's stability and potential. To minimize this, ensure proper compartmentalization (e.g., using a salt bridge or frit) and adequate stirring to prevent gas accumulation.