Facet Engineering of Pd Nanocrystals for Enhancing Photocatalytic Hydrogenation: Modulation of the Schottky Barrier Height and Enrichment of Surface Reactants

Abstract

Metal cocatalyst loading is one of the most widely explored strategies in promoting photocatalytic solar energy conversion. Engineering surface-active facets of metal cocatalyst and exploring how they modulate the reactivity is crucial for the further development of advanced photocatalysts. In this work, through controlled hybridization of two-dimensional (2D) TiO 2 nanosheets with well-designed Pd nanocube (Pd NC) with exposed {100} facet and Pd nano-octahedron (NO) with exposed {111} facet, we unravel the distinct crystal facet effect of Pd cocatalyst in promoting the selective hydrogenation of nitroarenes to amines of TiO 2 photocatalyst. The activity tests show that the Pd NO with {111} facet is a more efficient cocatalyst than the Pd NC with exposed {100} facet. The prepared TiO 2 -Pd NO composite displays a 900% enhancement of photocatalytic hydrogenation rate in comparison with bare TiO 2 , while the TiO 2 -Pd NC sample only shows a 200% photoactivity enhancement. Microscopic mechanism study discloses that the distinctive photoactivity improvement of Pd NO is ascribed to the concurrent modulation of the Schottky barrier height and enrichment of surface reactants: (i) the Pd NO with a lower Fermi level could result in steeper band bending of TiO 2 (i.e., higher Schottky barrier) than the Pd NC, which is more efficient in boosting interfacial separation and inhibiting the recombination of photoexcited charge pairs; and (ii) the {111} facet of Pd has higher nitroarenes adsorption ability and especially stronger hydrogen enrichment capability, thus accelerating the surface hydrogenation process and contributing to a higher reaction rate. This work emphasizes the rational facet control of cocatalysts for enhancing the photocatalytic hydrogenation performance.

Metal‐facilitated Photocatalytic Nanohybrids: Rational Design and Promising Environmental Applications

“…For CdS core‐Au shell photocatalyst, its photocatalytic activity was increased by more than 400 times in the splitting of water under irradiation of visible light compared to pure CdS [19] . A similar result was also demonstrated by using Pd‐hybridized TiO 2 nanosheets, which exhibited an increased hydrogenation rate by 900% than bare TiO 2 [20] . In addition, Ag‐doped g‐C 3 N 4 composite was utilized to completely degrade sulfamethoxazole within 20 min under irradiation of visible light [21]…”

Photocatalytic Anaerobic Oxidation of Aromatic Alcohols Coupled With H2 Production Over CsPbBr3/GO-Pt Catalysts

“…Figure 2B presents the electrochemical impedance spectroscopy (EIS) study of these samples, which is employed to study the charge transfer resistance of the samples. The hybrid CPB/GO-Pt shows the smallest arc diameter among these samples, demonstrating a more efficient charge transfer between the electrode and electrolyte solution over CPB/GO-Pt as compared with CsPbBr 3 and CPB/GO samples ( Lu et al, 2021 ). This result is consistent with the observation in photocurrent responses tests.…”

Few‐Layered MoxW1−xS2‐Modified CdS Photocatalyst: One‐Step Synthesis with Bifunctional Precursors and Improved H2‐Evolution Activity

“…[ 23–25 ] In this case, the widely reported H 2 ‐evolution cocatalyst is the noble metals (such as Pt, Au, Rh, and Pd), which can work effectively as a sink to trap the photoinduced electrons and provide a near‐zero overpotential for the surface H 2 evolution. [ 26–28 ] Nevertheless, the high cost and low availability of the noble metals are the main inherent limitations for their various wide applications. [ 29,30 ] Thus, it is quite essential to explore alternative high‐efficiency H 2 ‐evolution cocatalyst with low cost and natural abundance for the achievement of clean and sustainable hydrogen energy.…”