Efficient wide-spectrum photocatalytic overall water splitting over ultrathin molecular nickel phthalocyanine/BiVO4 Z-scheme heterojunctions without noble metals

Photocatalytic overall water splitting (OWS) is a promising route for sustainable production of hydrogen fuels. A grand challenge is developing efficient photocatalysts with extended light absorption, high charge separation and abundant catalytic sites. Here, we designed molecular nickel phthalocyanines on phosphate-functionalized bismuth vanadate nanosheets (NiPc/PO-BVNS) as ultrathin heterojunctions, targeting OWS without noble-metal cocatalysts or sacrificial agents. Optimal NiPc/PO-BVNS affords H2/O2 evolution rates of 23.89/ 12.23 mu mol g-1 h-1 with stoichiometric ratio under UV-vis irradiation, which reaches remarkable 50-fold enhancement over the benchmark g-C3N4/BVNS. The excellent photoactivities are ascribed to the novel Zscheme charge separation between NiPc and PO-BVNS, where phosphates are proved to induce quasi-singlemolecule-layer dispersion of NiPcs by H-bonding effect meanwhile create negative field to trap holes. Moreover, well-defined Ni2+-N4 center of NiPc could function as the catalytic sites for H2 evolution. This work diversifies the artificial photosynthesis systems with a facile strategy of constructing novel Z-scheme organic/ inorganic heterojunctions.

Automated summary

This study developed molecular nickel phthalocyanines on phosphate-functionalized bismuth vanadate nanosheets as ultrathin heterojunctions for photocatalytic overall water splitting without noble-metal cocatalysts or sacrificial agents. The Z-scheme charge separation between NiPc and PO-BVNS played a key role in achieving remarkable enhancement in H2/O2 evolution rates under UV-vis irradiation, showcasing a novel strategy for constructing artificial photosynthesis systems.