[dnautics]

Beyond the expensive of the metals another problem is duty cycles. Most transition metal catalysis is oxygen sensitive, and it seems like for some reason the first step of splitting water is creating oxygen. Plants go through great lengths to separate oxygen synthesis (photosystem II) from electron consumption. Most hydrogen production in lower organisms (like e coli) occurs entirely in anoxic conditions. Engineered systems for generating hydrogen via algae typically are temporally segregated (harvest light during day, produce hydrogen at night) which defeats the purpose and is also chemically steppy (carbohydrate intermediates).

[novaleaf]

> and it seems like for some reason the first step of splitting water is creating oxygen

good laugh on that :)

[nine_k]

Consider a split to H + OH as a first step, as opposed to H + H + O.

[dnautics]

What exactly are you proposing? What do you do with the OH?

[nine_k]

This is a possible first step of a water-splitting reaction that does not produce oxygen.

[dnautics]

I suggest going back to your chemistry text and reviewing mass balance, conservation of matter, and balancing equations.

What is that OH? Is it hydroxide radical? Hydroxide? Hydroxyl radical? Where does it go? Does it recombine to make hydrogen peroxide?

Btw... To make oxygen from water the first part of the first step is to split it into H and HO. You can't really break two bonds simultaneously, or anyways it's equivalent to doing them stepwise by the principle of microscopic reversibility.