What are the by-products of hydrogen-oxygen fuel cells?

The by-products of hydrogen-oxygen fuel cells are water and heat.

Hydrogen-oxygen fuel cells, also known as proton exchange membrane fuel cells (PEMFCs), are a type of fuel cell that uses hydrogen as the fuel and oxygen as the oxidant. The by-products of these fuel cells are water (H2O) and heat. This is because the hydrogen and oxygen combine in a chemical reaction to produce water, releasing energy in the form of heat in the process.

The chemical reaction that takes place in a hydrogen-oxygen fuel cell can be summarised as follows: 2H2 + O2 → 2H2O + heat. This reaction takes place in two steps. Firstly, at the anode (the positive electrode), hydrogen gas (H2) is split into two hydrogen ions (H+) and two electrons (e-). These electrons are then conducted through an external circuit, creating an electric current. Meanwhile, the hydrogen ions move through the proton exchange membrane to the cathode (the negative electrode).

At the cathode, oxygen gas (O2) is reduced by taking up the electrons from the external circuit and combining with the hydrogen ions to form water. This is the overall reaction that produces the by-products of water and heat.

The production of water and heat as by-products makes hydrogen-oxygen fuel cells environmentally friendly, as water is harmless and the heat can be used for useful purposes, such as heating buildings. Furthermore, unlike combustion reactions, this process does not produce any harmful greenhouse gases, making it a clean and sustainable source of energy.