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

Abstract

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 μmol 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 Z-scheme charge separation between NiPc and PO-BVNS, where phosphates are proved to induce quasi-single-molecule-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.