Magnetically stirrable photocatalysts binding the ZnS-decorated
Ni foam with the metal complex cocatalyst as a redox mediator and
light-absorbing composition were investigated. Loading metal complex
can improve light absorption, surface hydrophilicity, interfacial
charge migration, and H2 production activity. The variation
of the metal valences of the composite photocatalysts in an operando
environment (with sacrificial agent solution) with and without light
irradiation was investigated by X-ray absorption near-edge structure
(XANES) spectra and Fourier-transformed extended X-ray absorption
fine structure (EXAFS) spectra to monitor the charge carrier dynamics
of photocatalysis and explain how the macrocyclic Cu complex (CuC)
acted as a redox mediator better than the Ni complex. The smaller
valence difference of copper valence in ZS/CuC for dark and light
states revealed that the Cu complex facilitates a reversible electron
transfer between the ZnS photocatalyst and H+. Loading
the Cu complex can improve the separation of photogenerated carriers
by the redox couple of complexes, leading to a significantly improved
photocatalytic H2 production activity of 8150 μmol
h–1 g–1. The reactants can flow
through these magnetically stirrable Ni foam-based photocatalysts
by magnetic-field-driven stirring, which improves the contact between
photocatalysts and the sacrificial agents. The operando synchrotron
provides new insights for understanding the roles of redox mediators.