Synergistic Pd Single Atoms, Clusters, and Oxygen Vacancies on TiO₂ for Photocatalytic Hydrogen Evolution Coupled with Selective Organic Oxidation

Abstract

Developing efficient photocatalysts for synchronously producing H2 and high value‐added chemicals holds great promise to enhance solar energy conversion. Herein, a facile strategy of simultaneously engineering Pd cocatalyst and oxygen vacancies (VOs) on TiO2 to promote H2 production coupled with selective oxidation of benzylamine is demonstrated. The optimized PdSA+C/TiO2‐VO photocatalyst containing Pd single atoms (SAs), clusters (C), and VOs exhibits much superior performance to those of TiO2‐VO and PdSA/TiO2‐VO counterparts. The production rates of H2 and N‐benzylidenebenzylamine over PdSA+C/TiO2‐VO are 52.7 and 1.5 times those over TiO2‐VO, respectively. Both experimental and theoretical studies have elucidated the synergistic effect of Pd SAs, clusters, and VOs on TiO2 in boosting the photocatalytic reaction. The presence of Pd SAs facilitates the generation and stabilization of abundant VOs by the formation of PdOTi3+ atomic interface, while Pd clusters promote the photogenerated charge separation and afford the optimum active sites for H2 evolution. Surface VOs of TiO2 guarantee the efficient adsorption and dissociation/activation of reactant molecules. This study reveals the effect of active‐site engineering on the photocatalysis and is expected to shed substantial light on future structure design and modulation of semiconductor photocatalysts.

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

“…[ 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.…”

Single-atom catalysts for high-efficiency photocatalytic and photoelectrochemical water splitting: distinctive roles, unique fabrication methods and specific design strategies

“…The comparison of the photocatalytic HER activity of some typical precious metal-based SACs is listed in Table 2. 35,82,131,140,141,157,168,173,186,194,211,222,236,244,252,255,270,273,275,277,[291][292][293] Although the SA amounts in most of SACs were low, the selection of SA type displayed a crucial role in enhancing the photocatalytic activity of SACs. Compared with other precious SAs such as Au, Rh and Ag, Pt and Pd SAs exhibited far superior photocatalytic activity for the HER.…”

“…It has been reported that the defects of the substrates such as cation and anion vacancies play critical roles in determining the coordination environments and electronic structures of metal centers. 96,112,144,145,213,[244][245][246][247][248][249][250][251] More specically, substrates with vacancies can be used for effectively anchoring metal SAs in the preparation process due to the offered coupling sites. The vacancies on the support surface in SACs can avoid the aggregation of SAs, create strong interactions between SAs and the substrate and form metal-metal bonds to keep active metals atomically dispersed, signicantly improving the photocatalytic performance.…”

“…Very recently, a controllable construction of OVs on metal oxide surfaces to modulate the band structure and surface atomic arrangement of TiO 2 -based photocatalysts has been reported. 244 It was found that the Pd SAs facilitated the generation and stabilization of OVs in adjacent TiO 2 during the preparation and photocatalytic processes. In addition, the partially aggregated Pd NCs that formed in the preparation process promoted the separation/ transfer of photogenerated carriers while OVs functioned as active centers for the adsorption/dissociation of H 2 O when the photocatalytic HER was coupled with selective oxidation of benzylamine (Fig.…”

Nanoscale Self‐Wetting Driven Monatomization of Ag Nanoparticle for Excellent Photocatalytic Hydrogen Evolution

“…In further, the origin of excellent photocatalytic HER activity of SACs has been studied widely. [47][48][49][50] The SACs usually own extremely high ratio of exposed atoms and high atomic utilization efficiency. The superior photocatalytic HER performance of Ag 1 /CN than Ag NPs/CN stem from more visible light absorbtion ability, suitable electronic structure and hydrogen and the high atomic utilization efficiency.…”