Electrochemical behavior of the ZnO NWs/GO heterostructures. (a) CV curves of GO, ZnO NWs, ZnO NWs/GO heterostructure. (b) Magnified CV curve of GO. (c) Magnified CV curve of ZnO NWs. The scan rate of curves in (a-c) is 100 mV s−1. (d) CV curves of ZnO NWs/GO heterostructure at different scan rates.