Entropy-Increasing Single-Atom Photocatalysts Strengthening the Polarization Field for Boosting H₂O Overall Splitting into H₂

Entropy-increasing single-atom photocatalytic systems with a strengthened polarization field have been constructed by confining Ni atoms within interlayers of g-C3N4 nanotubes (Ni-C3N4Ts) by directly using the hydrothermal method for H2O overall splitting into H2 fuel. Theoretical and experimental results indicate that single-atom confinement increases the entropy of the system, which induces a strengthened polarization field, resulting in the smooth transfer of photogenerated e– and h+ from Ni-C3N4T interlayers to surface Ni-(s-triazine)4 active sites via Ni–N bonds as channels. Stable stoichiometric H2 and O2 evolution rates with an optimal solar-to-H2 efficiency of 1.23% have been obtained under AM 1.5 G solar simulator irradiation. Mechanistic studies based on density functional theory (DFT) calculations and in situ DRIFTS measurement confirm that abundant active sites for H2O overall splitting on the surface of the entropy-increasing single-atom system play the key role in translation, rotation, and transformation of protons and H2O intermediates for H2O reduction and oxidation.