Evaluation of the photoelectrochemical properties of mono and dual single-atom catalysts

Herein, we prepared poly(heptazine imide) (PHI), a layered structure of carbon nitride material containing sodium cations that were later exchanged, allowing us to obtain single-atom catalyst (SAC) sites of nickel, cobalt, and iron. In addition, combinations among these metals (NiCo, NiFe, and CoFe) were evaluated as dual single-atom catalysts (DSAC). The samples containing transition metal presented a photocurrent response far superior to the unmodified Na-PHI. The maximum photocurrent obtained was for the sample NiCo-PHI in alkaline media, being ~ 70 µA cm⁻² at 1.2 V vs. RHE; this value was higher than both Ni-PHI and Co-PHI combined, indicative of a cooperative effect in the DSAC sample. Lastly, all samples containing transition metal, when studied in acidic media, presented both cathodic and anodic photocurrent indicating a bifunctionality potential for application in both reduction and oxidation of water.