That looks like if it were paired with a cathode, you could take water and produce H2 more efficiently, but you'd need to keep the H+ sufficiently high or continue to supply it with more water, otherwise you develop higher OH- and H2O2 elsewhere in the solution from the H+ depletion, and that'll probably create some O2, but not at the rate you would with electrolysis, because the catalyzed reaction above would itself create a higher H+ environment, which feeds into itself from the H3O, but the H2 gas is escaping, depleting the H2 from the solution whereas the O2 is not gathering and escaping like that as much.
So, you could efficiently turn H2O into H2 source for a fuel cell.
But, you could also use this to make water more basic.
More detail:
Water is naturally a solution of H2, O2, H+, OH-, O--, H20, and H3O+, H2O2--. Except for H+ and O--, those are splitting and recombining most of the time while in liquid state, because the various ions in water and larger structures, etc. act as catalysts to the various reactions.
With light and the catalysts, the reaction above would seem to continue for quite a while, since the reaction produces H+ which will combine with surrounding H2O to product H3O.
Eventually, you're left with a greater concentration of OH- elsewhere in the solution (though surface of the catalyst near the reaction and the area above it that the H2 flows through would be more acidic). The reaction could stop if the availability of H3O and H2O would become too low, and at that point, the water would be more basic, because you wouldn't have sufficient free H+.
It's not one H20. I read the graphic as:
110 H30+ + 100 OH- -- 350-360nm UV light + Al-doped SrTiO3 selectively coloaded with Rh/Cr2O3 + CoOOH --> 210 H20 + 5 H2
That looks like if it were paired with a cathode, you could take water and produce H2 more efficiently, but you'd need to keep the H+ sufficiently high or continue to supply it with more water, otherwise you develop higher OH- and H2O2 elsewhere in the solution from the H+ depletion, and that'll probably create some O2, but not at the rate you would with electrolysis, because the catalyzed reaction above would itself create a higher H+ environment, which feeds into itself from the H3O, but the H2 gas is escaping, depleting the H2 from the solution whereas the O2 is not gathering and escaping like that as much.
So, you could efficiently turn H2O into H2 source for a fuel cell.
But, you could also use this to make water more basic.
More detail:
Water is naturally a solution of H2, O2, H+, OH-, O--, H20, and H3O+, H2O2--. Except for H+ and O--, those are splitting and recombining most of the time while in liquid state, because the various ions in water and larger structures, etc. act as catalysts to the various reactions.
With light and the catalysts, the reaction above would seem to continue for quite a while, since the reaction produces H+ which will combine with surrounding H2O to product H3O.
Eventually, you're left with a greater concentration of OH- elsewhere in the solution (though surface of the catalyst near the reaction and the area above it that the H2 flows through would be more acidic). The reaction could stop if the availability of H3O and H2O would become too low, and at that point, the water would be more basic, because you wouldn't have sufficient free H+.