Ultrathin p-n type Cu2O/CuCoCr-layered double hydroxide heterojunction nanosheets for photo-assisted aqueous Zn-CO2 batteries

As one of the promising avenues for resource utilization of CO2, photo-assisted Zn-CO2 batteries can not only consume CO2 to alleviate environmental problems, but also generate high-value chemicals and at the same time realize the generation of electrical energy. This technology can be described as "shoot two birds with one stone". However, the round trip efficiency of Zn-CO2 batteries has been a major obstacle for depth development. Herein, we report photo-assisted Zn-CO2 batteries over a Cu2O/CuCoCr-LDH (layered double hydroxide) photocathode with ultrathin p-n type heterojunction nanosheets fabricated by in situ reduction of the CuCoCr-LDH precursor which allowed the achievement of the photoelectric catalytic conversion of CO2 to CO (maximum product yield of 1167.6 mu mol g(-1) h(-1) and an outstanding selectivity of 90.14% under -1.0 V RHE). Compared with the photo-free Zn-CO2 counterpart, the discharge voltage for the photo-assisted Zn-CO2 battery increased to 1.22 V from 0.59 V and the round trip efficiency increased to 58.94% from 23.79%. This performance improvement can be attributed to the ultrathin p-n type heterojunction nanosheets on the photocathode for the effective separation of photogenerated electrons and holes, not only for the discharge process of CO2 reduction, but also for the charge process of water oxidation. This work confirmed that the ultrathin p-n type heterojunction nanosheets played a significant role for photogenerated carriers in Zn-CO2 batteries and provided a prospective and innovative approach for developing metal-CO2 electrochemical devices.