Photocatalytic–electrocatalytic dual hydrogen production system

• A photocatalytic-electrocatalytic dual hydrogen production system (PEHPS) was designed.
• 24.1 mLg−1 h−1 hydrogen evolution rate was observed with the CdZnS/10% Pt core–shell particles.
• S2O3−2 produced in the photocatalytic chamber was used as redox species in the electrocatalytic chamber.
• The potential of water electrolysis from 2.50 V to 1.70 V on the glassy carbon electrodes in the residual electrolyte.
• The over-potential of cathode coated with Poly-CoPc decreased as 0.230 V for HER.

In this paper, in order to produce efficient and low cost hydrogen by using alternative energies with simple ways; a photocatalytic–electrocatalytic dual hydrogen production system (PEHPS) which combined discontinuous photocatalytic and electrocatalytic systems in one continuous dual system was designed and optimized. In the photocatalytic chamber of PEHPS, nano-sized Cd(1 − x)ZnxS/Pt photocatalysts were utilized. The synthesized Cd(1 − x)ZnxS/Pt photocatalysts were characterized with scanning electron microscopy (SEM), X-Ray Diffraction (XRD) and diffuse reflectance UV–Vis spectroscopy. The most active photocatalyst having CdZnS2 core and 10% Pt shell showed 24.0 mLg−1 h−1 (963.6 μmol g−1 h−1) hydrogen evolution rate with 4.01% solar energy conversion efficiency (SECE%). S2O3−2S2O3−2 produced in the photocatalytic chamber of PEHPS was used as redox species in the electrocatalytic chamber. This process decreased the cell potential of water electrolysis from 2.50 V to 1.70 V on glassy carbon electrodes. Moreover, usage of electropolymerized metallophthalocyanines (Poly-MPc) as cathode active electrocatalyst, the over-potential of cathode of the electrocatalytic chamber for hydrogen reduction reaction decreased by 0.230 V.