What can be used as an electrolyte in water to perform electrolysis other than salt?
You can actually just use salt. It is because that the chemical reaction on the top is for one condition which is that your halide solution ($\ce{NaCl}$) has a very high concentration.

If you halide solution has lower concentration,the hydrogen ion and hydroxide ion in the water will discharged and the two half equation will be

$\ce{4H^+ + 4e^- -&gt; 2H_2}$

$\ce{4OH^- -&gt; 2H_2O + O_2 + 4e^-}$

So, the overall equation is

$\ce{4H^+ + 4OH^- -&gt; 2H_2 + 2H_2O + O_2}$

Thus, is okay to use salt.

Besides Salt

You can also use hydrochloric acid besides salt. Just remember that don't use a high concentration hydrochloric acid as the anode will just discharge the chloride ion instead of hydroxide ion.