Fabrication of CoO@ZnInS for photocatalytic hydrogen evolution: Insights into the synergistic mechanism of photothermal effect and heterojunction.

Integration of photothermal materials and photocatalysts can effectively improve photocatalytic hydrogen production. However, the synergistic mechanism of photothermal effect and heterojunction still need to be deeply investigated. Herein, CoO@ZnInS (ZIS) core-shell heterojunction was constructed as a photothermal/ photocatalytic integrated system for photocatalytic hydrogen production. The photothermal effect induced by CoO boosts the surface reaction kinetic of hydrogen evolution with an apparent activation energy decrease from 42.0 kJ⋅mol to 33.5 kJ⋅mol. The photothermal effect also increases the charge concentrations of CoO@ZIS, which ameliorates the conductivity of CoO@ZIS and thus benefits to charge transfer. In addition, a p-n junction forms between CoO and ZIS and provides a built-in electric field to enhance charge separate and prolong charge life time. Benefiting from the synergy of photothermal effect and heterojunction, the photocatalytic performance of CoO@ZIS is significantly improved with a highest hydrogen evolution rate of 4515 μmol⋅g⋅h, which is about 3.5 times higher than that of pure ZIS. This work offers a full perspective to understand the photothermal/photocatalytic integrated conception for solar hydrogen production.