Insight into the intrinsic driving force of NiCoP/ZnIn2S4−x boosting solar urea synthesis and hydrogen production

Urea not only can fertilizing more than quarter human beings, but also can be used in direct urea fuel cell. However, traditional multi-step Bosch–Meiser process consumes tremendous fossil energy and release greenhouse gas carbon dioxide. Therefore, renewable energy powered urea synthesis technique is priority. Herein, we developed a solar urea synthesis route from N 2 , CO 2 and H 2 O with S defected ZnIn 2 S 4 (ZnIn 2 S 4- x , ZIS) flowerlike microspheres as photocatalyst and NiCoP (NCP) nanoparticles as co-catalyst. The solar urea conversion rate reached to 13.9 μmol g −1 h −1 (15%-NCP/ZIS) at ambient temperature and 1 bar, which increased to 19.6 μmol g −1 h −1 (15%-NCP/ZIS) with mild rising temperature (80 ℃) and pressure (10 bar). Moreover, the solar urea conversion rate at mild pressure (1 bar to 10 bar) shows the same tendency as hydrogen production for NCP/ZIS photocatalysts. Smaller ΔG H* energy and spin-polarization effect of dual function photocatalyst NCP/ZIS serve as the driving force for the urea synthesis and hydrogen production. This work opens a new avenue for searching highly efficient solar urea conversion photocatalysts. • NiCoP/ZnIn 2 S 4- x heterojunction was constructed for urea synthesis. • Photocatalytic urea synthesis by coupling CO 2 and N 2 in water under visible light. • NiCoP/ZnIn 2 S 4- x shows superior photocatalytic activity than 1%Pt/ ZnIn 2 S 4- x . • The driving force of NiCoP as superior cocatalyst is mainly spin-polarisation effect.