Monovacant Janus WSSe designed as a bifunctional photocatalyst for OER and CO2RR with multiple C1 products

The photocatalytic CO₂RR is a promising strategy for carbon neutrality, while OER is a crucial half-reaction in energy storage and conversion processes, including water splitting, CO₂RR and metal-air batteries. However, developing effective and eco-friendly photocatalysts remains challengeable. In this study, Janus WSSe with monovacant Se (V_Se-WSSe) is designed as a bifunctional photocatalyst. Based on the evaluation of the thermodynamic stability and *CO₂ capability, the light absorption and photocatalytic performance of CO₂RR and OER are systematically investigated. In the lower energy range of visible light, V_Se-WSSe has better light absorption than pristine WSSe, facilitating photocatalytic efficiency. As for CO₂RR, all possible reaction pathways and multiple C1 products are explored, demonstrating that the products of HCOOH, CH₃OH and CH₄ have U_L values of -0.97 V, -1.52 V and -1.57 V, respectively. The photogenerated electrons potential of 0.69 eV at pH=0 will reduce the U_L values of CH₃OH and CH₄ to -0.83 V and -0.88 V, respectively. Moreover, the CO₂RR can greatly suppress the competitive HER. The PDS of OER occurs at the step of H₂O→*OH with U_L= -1.57 V. The photogenerated holes potential of 1.57 eV can make all the hydrogenation steps go downhill and result in a spontaneous reaction. This research unveils the new possibility of monovacant Janus WSSe as a bifunctional photocatalyst for CO₂RR and OER, which opens the application avenue of Janus materials.