Topotactic and Self-Templated Fabrication of Zn_1–xCd_xSe Porous Nanobelt–ZnO Nanorod for Photoelectrochemical Hydrogen Production

Abstract

Herein, we propose the topotactic and self-templated fabrication of Zn1–x Cd x Se porous nanobelt–ZnO nanorod (termed as ZnCdSe/ZnO) photoelectrode via the cadmium (Cd2+) ion-exchange process on zinc (Zn) foil. Inorganic–organic hybrid ZnSe­(en)0.5 nanobelt (NB) was synthesized on Zn foil by a facial solvothermal method at different temperatures of 140, 160, and 180 °C for 12 h. The interfacial properties and photoelectrochemical (PEC) performance of inorganic–organic ZnSe­(en)0.5 NB fabricated through the Cd2+ ion-exchange method at different time durations of 6, 12, 18, and 24 h at 140 °C were investigated. The TEM analysis results indicate that the inorganic–organic ZnSe­(en)0.5 NB transformed into ZnCdSe and a self-assembled ZnO formed on the Zn foil. In particular Cd2+ ion temperature (140 °C/18 h), the optimized ZnCdSe/ZnO-(F) photoelectrode shows an excellent photocurrent density of 14 mA·cm–2 at 0 V vs Ag/AgCl with 219 μmol·cm–2 hydrogen gas evolution for 3 h under 1 sun illumination. The higher photocurrent value resulted from the optimum growth of ZnO, the formation of porous ZnCdSe, and the effective electrolyte penetration for electron–hole pair separation. The photoluminescence spectroscopy shows that the photoexcited charged carriers promoted a longer lifetime. Furthermore, we provide a full account of the possible charge-transfer mechanism during PEC hydrogen production.

Development of Dual-Nanoarchitecture Photoanodes Based on Microwave-Assisted ZnS(en)0.5 Nanoplates for Photoelectrochemical Hydrogen Generation

“…In addition, thorough inspections revealed that the significant enhancement of the XRD peak intensities for CdS was caused by the increased crystallinity after Cd 2+ -ion exchange. However, the absence of a major peak for the inorganic–organic hybrid material at a low diffraction angle indicated the release of EN from the ZnS­(en) 0.5 structure, in Figure f. , Furthermore, the FTIR results signified that the absence of −CH and −NH groups in the Zn 1– x Cd x S PNP/ZnO NR160 photoanode implies the transformation of the obtained material into an inorganic form, as portrayed in Figure S9 (Supporting Information). In addition, these FTIR results were consistent with the XRD results.…”

“…Consequently, a smaller R ct2 value can contribute toward effective charge transport at the electrode/electrolyte interface. 17,34,35 However, the higher charge transfer resistance (R ct1 ) in the Zn 1−x Cd x S PNP/ZnO NR180 photoanode was caused by the increased surface-reaction barrier path proximate to the porous site of the dilapidated structure of the Zn 1−x Cd x S PNP in this dual-nanoarchitecture system. 40,41 The EIS results were consistent with the J−V curves (Figure 3a).…”

“…However, the optimum porosity and growth of ZnO NRs is advantageous for diminishing the hole transport between the electrode−electrolyte interface during photoelectrochemical hydrogen evolution. 26,34 Moreover, as the temperature increased further from 160 to 180 °C, major morphological alterations were observed in the self-assembled ZnO NR and Zn 1−x Cd x S PNP. As displayed in Figure 2c, the 17 Moreover, the intensity of the ZnO NR XRD peaks increased with increasing Cd 2+ -ion exchange temperature owing to the spontaneous growth of ZnO NRs.…”

“…Thus, careful inspection revealed that the ZnS­(en) 0.5 NP completely covered the Zn 1– x Cd x S PNP without disturbing the PNP frame as the Cd 2+ -ion exchange temperature increased from 140 to 160 °C (Figure b). However, the optimum porosity and growth of ZnO NRs is advantageous for diminishing the hole transport between the electrode–electrolyte interface during photoelectrochemical hydrogen evolution. , Moreover, as the temperature increased further from 160 to 180 °C, major morphological alterations were observed in the self-assembled ZnO NR and Zn 1– x Cd x S PNP. As displayed in Figure c, the Zn 1– x Cd x S PNP/ZnO NR180 photoanode comprised dense ZnO NRs with a stacked structure.…”

Tunable Bandgap Engineering of ZnxCd1−xSe Solid Solution with Controlled Ratio via a Facile One‐Pot Synthesis for Visible‐Light Photocatalytic H2 Production

“…[ 10 ] In analogy with the traditional Zn x Cd 1− x S solid solutions, [ 11 ] the band structures of the corresponding metal selenides (Zn x Cd 1− x Se) can be adjusted by tuning the ratio of Zn/Cd precursors [6c,12] . However, unlike Zn x Cd 1− x S, the Zn x Cd 1− x Se nanostructures were generally prepared by various synthetic routes, such as solid‐state reaction, [6c] ion‐exchange methods, [ 13 ] diethylenetriamine template‐assisted, [ 14 ] solvothermal, [ 15 ] and a multiple‐step process. [ 16 ] Nevertheless, most of the reported approaches involving Zn x Cd 1− x Se nanostructures suffer from irregular structures and complicated preparation conditions, hindering their practical application.…”