第一作者：西北工业大学 Jiankang Zhang, 中国科学院上海高等研究院 Panzhe Qiao
通讯作者：中国石油大学 脱永笑，西北工业大学 覃勇
DOI：https://doi.org/10.1021/acscatal.4c03593
将单原子（SA）、纳米簇（NC）、氧空位（Ov）等不同的反应位点整合到特定的光催化剂中，为突破SA催化的局限性提供了新的前景。然而，助催化剂尺寸和Ov对光催化性能和协同作用的内在影响机制仍未得到很好的揭示。作者报道了原子层沉积法合成和研究了原子分散的Pt基光催化剂，并将其表面限制在含有Ov的多孔TiO2纳米花中。SA-NC共存的PtSA+NC@TiO2光催化剂表现出最佳的析氢活性（2260 h-1），比PtSA@TiO2光催化剂高3.6倍。此外，通过调整助催化剂的尺寸和Ov浓度，催化活性可进一步显著提高至3645 h-1。通过表征和密度泛函理论计算，作者确定了反应分子的吸附/解吸位点，并揭示了活性物质的协同催化机制：Pt NC对优先吸附在Ti位点的H2O分子进行吸附解离，同时降低了对H2分子进行解吸的Pt SA的d带中心，相邻的Ov稳定了助催化剂并改变了Pt NC的电子能分布，从而达到了对*OH中间体的最佳吸附状态。本文提出的多位点工程概念和机理见解，有望为原子分散光催化剂的合理设计提供启示。
Figure 1. Synthesis and structure of the photocatalysts. (a) Synthetic process of the confined Pt@TiO2 photocatalysts (TBOT, IPA, and DMF represent tetrabutyl titanate, isopropanol, and N,N-dimethylformamide, respectively). (b) SEM image of TiO2 nanoflower spheres synthesized by solvothermal synthesis (SS). (c) XRD patterns of the four photocatalysts. (d) HAADF-STEM image of the PtSA@TiO2 photocatalysts. (e) HAADF-STEM and (f) the corresponding elemental mapping images of the PtSA+NC@TiO2 photocatalysts. (g) HAADF-STEM, HRTEM images (inset), and the corresponding histogram of particle size distribution (inset) of the PtNP@TiO2 photocatalysts.
Figure 2. Physicochemical properties and activity evaluation of the photocatalysts. (a) N2 adsorption−desorption isotherms and (b) the corresponding pore size distribution curves of the four photocatalysts. (c) CO−DRIFTS spectra of the three photocatalysts. (d) XPS Pt 4f spectra of the three photocatalysts. (e) The continuous profiles of photocatalytic H2 evolution (20 vol % methanol−aqueous) and (f) the corresponding H2 evolution rates over the photocatalysts (50 mg) under ultraviolet−visible (UV−Vis) light irradiation.
Figure 3. Structure modulation and characterization. (a) The modulation of cocatalyst size versus Ov concentrations by H2 activation treatment. (b) H2-TPR profiles of bare TiO2 and PtSA+NC@TiO2 photocatalysts. (c) Schematics of the active spillover H· effect. (d) The color comparison of the photocatalysts (AP represents as-prepared). (e) EPR spectra obtained at 298 K, (f) UV−Vis spectra, and (g) the zeta potential of the photocatalysts.
Figure 4. Structural and electronic properties of the activated photocatalysts. The HAADF-STEM images of the activated (a) PtSA+NC@TiO2-175R, (b) PtSA+NC@TiO2-300R, and (c) PtSA+NC@TiO2-475R photocatalysts. (d) CO−DRIFTS spectra of the PtSA+NC@TiO2 and representative PtSA+NC@TiO2-475R photocatalysts. (e) Pt LIII-edge k3-weighted EXAFS spectra and (f) normalized Pt LIII-edge XANES spectra of the photocatalysts and reference Pt foil and PtO2. (g) WT-EXAFS spectra of PtSA+NC@TiO2, PtSA+NC@TiO2-475R photocatalysts, Pt foil, and PtO2. XPS (h) Pt 4f, (i) Ti 2p, and (j) O 1s spectra of the photocatalysts.
Figure 5. PHE activity evaluation of the photocatalysts. (a) Continuous profiles of photocatalytic H2 evolution (20 vol % methanol−aqueous) of the photocatalysts under UV−Vis light irradiation. (b) The corresponding TOF value, SA/NC ratio, and Ov content of the photocatalysts. (c) Transient photocurrent responses of the photocatalysts. (d) Continuous H2 evolution profiles from AB solution (0.05 mol/L AB, 30 °C) over the photocatalysts under dark (D) and UV−vis light (L) irradiation.
Figure 6. Charge transfer−separation efficiency of the photocatalysts. (a) PL spectra of the photocatalysts. (b) The potential reaction mechanism (SS represents the shallow state). (c) 2D contour plots of the TA spectra of the representative (d) TiO2, (e) PtSA+NC@TiO2, and (f) PtSA+NC@TiO2-475R photocatalysts at 350 nm excitation, and the corresponding TA decay kinetics probed at 630 nm for the (g) TiO2, (h) PtSA+NC@TiO2, and (i) PtSA+NC@TiO2-475R photocatalysts.
Figure 7. TPD and DFT calculation results. (a) H2O-TPD and (b) H2-TPD profiles of the photocatalysts. (c) Free energy diagrams for the watersplitting process over the photocatalysts. (d) The configuration of *H2O, *H−*OH, and *H on the TiO2-confined PtSA@TiO2, PtNC@TiO2, PtSA+NC@TiO2, and PtSA+NC@TiO2−Ov (i.e., PtSA+NC@TiO2-R) photocatalysts. (e) Three-dimensional charge density difference of Pt on the photocatalysts with an isosurface value of 0.03 eV Å−3. Electron accumulation is yellow, and depletion is blue. (f) Total DOS of TiO2 for the photocatalysts. (g) Schematics of the synergistic photocatalytic mechanism over the Pt SA−NC−Ov sites. Red, yellow, purple, and white spheres depict O, Ti, Pt, and H atoms, respectively.
Species Heterogeneity and Synergy to Boost Photocatalytic Hydrogen Evolution
https://doi.org/10.1021/acscatal.4c03593
