Multication and Structure Regulation: Utilizing X‐Doped (X = Co, Mn, Cu) ZnS/CoO Hollow Composites to Spatially Propel the Charge for Superior Solar Hydrogen Evolution

Abstract

The rise of global energy demand has spurred ongoing search for high-efficiency photocatalysis technology for achieving economically viable solar to renewable energy conversion, such as the hydrogen evolution reaction (HER, ΔG ¼ þ237 kJ mol À1 ). [1] However, the well-known "backward electron transfer effect" always leads to low solar energy conversion efficiency for practical application. As one of the most efficient systems, solar-driven p-n heterostructured photocatalysts have been regarded as a promising candidate for sustainable H 2 generation due to their unique built-in electric field and stability. [2][3][4] The "charged" space created by combining p-type and n-type semiconductors can provide additional driving force to extend the separation of light-stimulated charge carriers, thereby suppressing back electron transfer in the targeted reaction. In the past 10 years, numerous p-n heterojunctions have been devoted to photocatalytic water splitting with significant progress realized to date. [5][6][7][8] However, the reached performance is still not sufficient mainly due to the bulk and aggregate structure used in the p-n heterojunction. [9][10][11][12][13] Therefore, in addition to choosing the appropriate components, it is important to design rational structural morphology for heterostructure to synergistically enhance the solar-to-hydrogen conversion efficiency.As a precious metal-free metal sulfide, zinc sulfide (ZnS, n-type) can be fabricated with different morphologies to fine-tune its photocatalytic water-splitting efficiency, and its low-cost and scalable physicochemical properties make it highly suitable for wide-scale implementation without compromising its inherent high catalytic activity. [14][15][16] In particular, the hollow ZnS structure prepared by different methods has multiple unique photocatalytic advantages: 1) the thin-shelled substrate could shorten diffusion distance to accelerate interfacial charge transfer efficiency; [17,18] 2) hollow structure enhances the surface-to-volume ratio to expose ample reactive sites for surface-related redox reaction; and [19,20] 3) optical scattering/reflection caused by internal cavity conduce to improve the light-harvesting ability, especially in multifacet hollow frameworks. [21] It is worth noting that the

MOF-derived CdS/CoO S-type heterojunctions for improving the efficiency of photocatalytic evolution

“…Meanwhile, the average difference in the electron density (Δρ) of the CdS/ CoO heterojunction along the Z-direction was calculated (Fig. 7(g)), and the results indicated the electron transfer from CdS to CoO, 32 and these results were consistent with the experimentally obtained results.…”

Z-Scheme CdIn2S4/Bi2WO6 Heterojunction for High Piezo-Photo Synergetic Performance

“…To study the carrier separation of catalysts, photoluminescence (PL), electrical impedance (EIS), and transient photocurrent (LSV) were carried out. − The PL intensity of 10% CIS/BWO is significantly lower than that of BWO, which may be due to the fact that the piezoelectric field formed in 10% CIS/BWO can effectively enhance the carrier separation efficiency (Figure a). Furthermore, the photocurrent of 10% CIS/BWO is higher than that of BWO, confirming that the piezoelectric field can increase the electron and hole separation of 10% CIS/BWO (Figure b).…”

Cation exchange doping by transition and non-transition metals: embracing luminescence for band gap tunability in a ZnS lattice

“…14 The incorporation of foreign atoms in the nanocrystals is an efficient method for synchronizing the energy levels, stabilizing the surface states, as well as influencing the structural features of semiconductors. 15 The prerequisite for this strategy relies on doping a suitable element that interacts with the frontier molecular orbitals of the host lattice. The controlled incorporation of transition and non-transition metal dopants into ZnS QDs has opened up new avenues for tailoring their properties and expanding their potential applications.…”

“…Non-transition metal doping, on the other hand, enables control over bandgap energy, facilitating applications in photovoltaics, photocatalysis, and energy storage. 15,16 Transition element dopants in the ZnS lattice can introduce various effects:…”