High-entropy layered oxides nanosheets for highly efficient photoelectrocatalytic reduction of CO2 and application research

High-entropy oxides receive significant attention owing to their “four effects”. However, they still suffer from harsh construction conditions such as high temperature and high pressure and present a block-like structure. Herein, in this work, Ni-Mn-Cu-Co-Fe-Al high-entropy layered oxides (HELOs) with a layered nanosheet structure were constructed by a simple pathway of topological transformation under relatively low temperature (300 °C) with six-membered Ni-Mn-Cu-Co-Fe-Al layered double hydroxides (LDHs) precursors, which exhibited an outstanding activity and excellent selectivity for CO2 photoelectroreduction (obtaining the highest carbon monoxide yield of 909.55 µmol·g−1·h−1 under −0.8 V vs. reversible hydrogen electrode (RHE), which is almost twice that of pure electrocatalysis). In addition, the charging voltage of a photo-assisted Zn-CO2 battery with HELOs as electrode was reduced from 2.62 to 2.40 V; the discharging voltage of the battery was increased from 0.51 to 0.59 V with the assistance of illumination. The improvement of round-trip efficiency of the battery indicates that light played a positive role in both the charging and discharging processes. This study not only lays an important foundation for the development of high-entropy oxides but also expands their application in the field of photoelectrochemistry.