Photoelectrocatalytic Reduction of CO₂ to Paraffin Using p-n Heterojunctions

Nowadays, photoelectrocatalytic (PEC) reduction of CO₂ represents a very promising solution for storing solar energy in value-added chemicals, but so far it has been hampered by the lack of highly efficient catalyst of photocathode. Enlightened by the Calvin cycle of plants, here we show that a series of three-dimensional C/N-doped heterojunctions of Zn_x:Co_y@Cu are successfully fabricated and applied as photocathodes in the PEC reduction of CO₂ to generate paraffin product. These materials integrate semiconductors of p-type Co₃O₄ and n-type ZnO on Cu foam to construct fine heterojunctions with multiple active sites, which result in excellent C-C coupling control in reduction of CO₂. The best catalyst of Zn_0.2:Co₁@Cu yields paraffin at a rate of 325 μg·h^-1 under -0.4 V versus saturated calomel electrode without H₂ release. The apparent quantum efficiency of PEC cell is up to 1.95%.