# Why should we be interested in catalyst for electrolysis?

I've been reading papers on Phosphided metals (CoP, NiP, FeP) as a catalyst for electrolysis. They increase the current density of the cell for a voltage. If it still requires 39.4 kilowatt-hours per kilogram of hydrogen (https://en.wikipedia.org/wiki/Electrolysis_of_water), why does it matter how fast the reaction occurs?

For example, with no catalyst, an electrolyzer runs at 0.6A/cm2 at 2.3V or with a catalyst it runs at 1A/cm2 at 1.4V. Both cases require about the same amount of power and should produce the same amount of hydrogen, correct?

• The two examples you provide do not produce the same amount of hydrogen. Electrons are "stoichometric reagents/products" which can be indirectly measured in coloumbs ($\mathrm{1\ mol\ e^- =96485\ C}$). A higher current means more starting material is being consumed (or more product is being formed) for a given amount of time (recall that $\mathrm{1\ A=1\ C/s}$). This means that your second example would theoretically produce hydrogen $\mathrm{1/0.6=1.67}$ times faster. The lower voltage also decreases the chance of electrochemical side-reactions which would also consume/release electrons. – Nicolau Saker Neto Dec 8 '19 at 14:41

$$E=2 \cdot U \cdot F$$
where $$U$$ is the used voltage $$F$$ is the Faraday's constant cca 96490 C/mol