Solid Solution Photocatalyst with Spontaneous Polarization Exhibiting Low Recombination Toward Efficient CO2 Photoreduction.

Decreasing the recombination of photogenerated carriers is a major challenge for efficiently converting solar energy into chemical energy by photocatalysis. Here, we have demonstrated that growth of a polar GaN:ZnO solid solution single crystal along its polarization axis is beneficial to efficient separation of photogenerated carriers, owing to the periodic potential barriers and wells generated from the periodically positive and negative atom arrangements in crystal structure. Local charge imbalance caused by replacing Ga3+ with Zn2+ leads to a polarization vector in the {0001} planes of GaN:ZnO solid solution, thus forming a 1D electron transport path along in the {0001} planes of GaN:ZnO solid solution to decrease recombination. Shorting the hole-transport distance by synthesizing porous nanoplates can further decrease recombination under the polarization field and improve the performance of polar photocatalyst in photoreduction of CO2 into CH4.