The hydrogen evolution reaction (HER) is a chemical reaction that occurs in an electrolyzer during water electrolysis to produce hydrogen gas:

 The hydrogen evolution reaction (HER) is a chemical reaction that occurs in an electrolyzer during water electrolysis to produce hydrogen gas: 

 

• Explanation

  The HER is a half-cell reaction that takes place at the cathode of an electrolyzer, where water is reduced to produce hydrogen. The other half-cell reaction is the oxygen evolution reaction (OER), which takes place at the anode to produce oxygen. 

   
• Importance

  The HER is a clean and efficient way to produce hydrogen fuel. Hydrogen is considered a renewable resource and a potential alternative to fossil fuels. 

   
• Catalysts

  The HER typically requires a catalyst to convert protons to hydrogen. In commercial electrolyzers, supported platinum is often used as the catalyst at the anode. 

   
• Challenges

  The HER can be sluggish due to high overpotentials, which are a measure of kinetic energy barriers. To achieve large-scale hydrogen production, it's important to develop active, stable, and low-cost electrocatalysts. 

   

To test if a gas is hydrogen, you can bring a burning match to the mouth of the tube where the gas is evolving. If the match catches fire and makes a "pop" sound, then the gas is hydrogen