Nowhere is it stated how efficient either material is, other than to say that the researchers are 5-10 years away from a material that's 10% efficient. So they must have an efficiency of less than that I guess.

From the paper, the closest I can see is:

The applied bias photon-to-current efficiency (ABPE) of the Ni(OH)2/Co3O4/3C-SiC photoanode reached 0.47% at 0.65 V vs RHE, which is 15.6 and 1.8 times higher than that of the 3C-SiC and Co3O4/3C-SiC photoanodes, respectively (Figure 4b)

I don't know how representative that measurement is though.

[–] Hirom@beehaw.org 1 points 1 week ago* (last edited 1 week ago)

Good question.

The paper's PDF give clearer, less click-baity information on efficiency:

The applied bias photon-to-current efficiency (ABPE) of the Ni(OH)2/Co3O4/3C-SiC photoanode reached 0.47% at 0.65V vs RHE, which is 15.6 and 1.8 times higher than that of the 3C-SiC and Co3O4/3C-SiC photoanodes, respectively (Figure 4b).

A 8x increase is good progress for that specific technique, but 0.47% is very low efficiency. There's still ways to go.