Porous Zn1-xCdxS nanosheets/ZnO nanorod heterojunction photoanode via self-templated and cadmium ions exchanged conversion of ZnS(HDA)0.5 nanosheets/ZnO nanorod

Abstract

Herein, we synthesized porous Zn1-xCdxS nanosheets (PNS)/ZnO nanorod (NR) heterojunction photoanode via self-templated conversion using successively hydrothermal and Cd2+ ion exchange methods. Moreover, after conversion of ZnO to inorganic–organic hybrid ZnS-1,6-hexanediamine (HDA)0.5nanosheets/ZnO NR material, Cd2+ ion exchange was conducted. It was confirmed from X-ray photoelectron spectroscopy (XPS) and Transmission electron microscopy (TEM) analyses that the inorganic–organic hybrid ZnS(HDA)0.5 NS was transformed into Zn1-xCdxS PNS/ZnO NR heterojunction photoanode via the replacement of Zn2+ by Cd2+ ion. Zn1-xCdxS PNS/ZnO NR-160C3H heterojunction photoanode synthesized at 160 °C for 3 h showed the highest photocurrent density of 4.10 mA cm−2 (vs. RHE) under 1.5 G illumination, which was 7.9 times higher than that of bare ZnO NR photoanode. The porous nanostructured morphology and larger surface area of Zn1-xCdxS PNS/ZnO NR heterojunction photoanode fabricated by Cd2+ ion exchange result in efficient light absorption and effective charge transfer pathway. The photoluminescence (PL) and time-resolved photoluminescence (TRPL) results show the shorter lifetime (37 ns) and reduced recombination in Zn1-xCdxS PNS/ZnO NR-160C3H heterojunction photoanode. During PEC analysis, the possible charge transfer mechanism in Zn1-xCdxS PNS/ZnO NR heterojunction photoanode was proposed. Surface passivated Zn1-xCdxS PNS/ZnO NR-160C3H photoanode shows improved photostability and exhibited 3.8 times higher H2 evolution (161 μmol) than the Zn1-xCdxS PNS/ZnO NR-160C3H (42 μmol) photoelectrode at 0.9 V vs. RHE.