Enhanced Charge Separation for Efficient Photocatalytic H2 Production by Long-Lived Trap-State-Induced Interfacial Charge Transfer

Achieving Long-Lived Charge Separated State through Ultrafast Interfacial Hole Transfer in Redox Sites-Isolated CdS Nanorods for Enhanced Photocatalysis

As opposed to natural photosynthesis, a significant challenge in a semiconductor-based photocatalyst is the limited hole extraction efficiency, which adversely affects solar-to-fuel efficiency. Recent studies have demonstrated that photocatalysts featuring spatially isolated dual catalytic oxidation/reduction sites can yield enhanced hole extraction efficiencies. However, the decay dynamics of excited states in such photocatalysts have not been explored. Here a ternary barbell-shaped CdS/MoS2/Cu2S heterostructure is prepared, comprising CdS nanorods (NRs) interfaced with MoS2 nanosheets at both ends and Cu2S nanoparticles on the sidewall. By using transient absorption (TA) spectra, highly efficient charge separation within the CdS/MoS2/Cu2S heterostructure are identified. This is achieved through directed electron transfer to the MoS2 tips at a rate constant of >8.3 × 109 s-1 and rapid hole transfer to the Cu2S nanoparticles on the sidewall at a rate of >6.1 × 1010 s-1, leading to an exceptional overall charge transfer constant of 2.3 × 1011 s-1 in CdS/MoS2/Cu2S. The enhanced hole transfer efficiency results in a remarkably prolonged charge-separated state, facilitating efficient electron accumulation within the MoS2 tips. Consequently, the ternary CdS/MoS2/Cu2S heterostructure demonstrates a 22-fold enhancement in visible-light-driven H2 generation compare to pure CdS nanorods. This work highlights the significance of efficient hole extraction in enhancing the solar-to-H2 performance of semiconductor-based heterostructure.

Interfacial electron modulation of 2D nanopetal ZnIn2S4 with edge-decorated Ni clusters for accelerated photocatalytic H2 evolution

Heterostructure interfacial engineering between photocatalyst and co-catalyst to obtain an optimized electronic structure is a promising approach to improving their performance in the photocatalytic hydrogen evolution reaction (HER). In this work, two-dimensional nanopetal-like ZnIn2S4 (ZIS) with an adequately exposed active (110) edge facet-decorated Ni cluster heterostructure was prepared via chemical bath deposition, followed by photodeposition. In the catalyst preparation, the ZIS microstructure was modulated to sufficiently expose the active sites of the (110) edge for the HER, on which spontaneous interfacial engineering with an additional Ni cluster co-catalyst would be triggered via photodeposition in situ. The hydrogen production rate of the composite photocatalyst was excellent, at up to 26.80 mmol g-1 h-1 under simulated sunlight, which was 15.4 times greater than that of pristine ZIS. The optimized photocatalyst achieved a state-of-the-art apparent quantum yield of 61.68% at a single wavelength of 420 nm. Combined with systematic experimental characterization and density functional theory calculation, it was demonstrated that the separation and migration of charge carriers were significantly enhanced via the Ni cluster-induced interfacial electron redistribution, which contributed to the near-zero Gibbs free energy barrier and favored intermediate (*H) adsorption and desorption behavior, resulting in the superior photocatalytic performance. In summary, this work enables tuning of the interfacial electronic properties via spontaneous photodeposition of metallic cluster co-catalyst on the edge active sites, through which the separation of photogenerated charge carriers and surface redox reactions can be synergistically facilitated.

Room-Temperature Synthesis of Highly-Efficient Eu3+-Activated KGd2F7 Red-Emitting Nanoparticles for White Light-Emitting Diode

Luminescent materials with high thermal stability and quantum efficiency are extensively desired for indoor illumination. In this research, a series of Eu³⁺-activated KGd₂F₇ red-emitting nanoparticles were prepared at room temperature and their phase structure, morphology, luminescence properties, as well as thermal stability, have been studied in detail. Excited by 393 nm, the resultant nanoparticles emitted bright red emissions and its optimal status was realized when the Eu³⁺ content was 30 mol%, in which the concentration quenching mechanism was triggered by electric dipole-dipole interaction. Through theoretical analysis via the Judd-Ofelt theory, one knows that Eu³⁺ situates at the high symmetry sites in as-prepared nanoparticles. Moreover, the internal and extra quantum efficiencies of designed nanoparticles were dependent on Eu³⁺ content. Furthermore, the studied nanoparticles also had splendid thermal stability and the corresponding activation energy was 0.18 eV. Additionally, via employing the designed nanoparticles as red-emitting constituents, a warm white light-emitting diode (white-LED), which exhibits low correlated color temperature (4456 K), proper luminous efficiency (17.2 lm/W) and high color rendering index (88.3), was developed. Our findings illustrate that Eu³⁺-activated KGd₂F₇ nanoparticles with bright red emissions are able to be used to promote the performance of white-LED.