Pd-Decorated PdO Hollow Shells: A H₂-Sensing System in Which Catalyst Nanoparticle and Semiconductor Support are Interconvertible

Abstract

Developing a simple strategy to fabricate high-performance hydrogen sensors with long-term stability remains quite challenging. Here, we report the H 2 -sensing performance of Pd-decorated PdO hollow shells (Pd/PdO HSs). In this novel system, the catalyst nanoparticles (Pd NPs) and semiconductor support (PdO) are interconvertible, which is different from traditional hydrogen-sensing systems such as Pd/TiO 2 and Pd/ZnO. This Pd/ PdO system exhibits multiple unique properties. First, well-distributed Pd NPs with controllable density can be decorated on PdO support through a one-step NaBH 4 treatment during which PdO is partially reduced into Pd. Second, the decorated Pd NPs are physically inlaid in the PdO support, which not only prevents the agglomeration or detachment of Pd NPs but also enhances the electron transfer between Pd NPs and PdO. Third, Pd/PdO HSs can be reoxidized into PdO HSs once their sensing performance degrades, which repeatedly manipulates Pd/PdO HSs under the initial reduction process, leading to the reactivation of the sensing performance. With all these advantages, Pd/PdO HSs demonstrate a detection limit lower than 1 ppm, a response/ recovery time to 1% H 2 of 5 s/32 s at room temperature, and a repeatable reactivation ability. The strategy presented here is convenient and time saving and has no need to prefunctionalize the PdO surface for the decoration of catalyst NPs. Moreover, the unique reactivation ability of Pd/PdO system opens a new strategy toward extending the lifetime of H 2 sensors.

Controllable Fabrication of PdO‐PdAu Ternary Hollow Shells: Synergistic Acceleration of H2‐Sensing Speed via Morphology Regulation and Electronic Structure Modulation

“…The characteristic XRD peak of Pd disappears after calcination, and new peaks appear at 34.5°, 42.1°, 55°, and 61°, corresponding to the (101), (110), (112), and (200) planes of PdO. [ 21 ] In addition, the signals corresponding to the lattice O in PdO and adsorbed dioxygen (or OH) on the PdO surface appear in the O 1s XPS spectra of AuPd HSs after calcination (Figure 2B), [ 27,28 ] implying the formation of PdO‐Au HSs. During the subsequent reduction step, the Pd (111) XRD peak appears again, and the intensity ratio of the Pd (111) to the PdO (101) peak gradually increases with the prolonging of the reduction time.…”

“…This phenomenon relates to the electron transfer from Pd to PdO because of their different work function (PdO of 6.4 eV vs Pd of 5.1 eV). [ 21 ] At the reduction time of 20 min, both Pd 0 and Pd 2+ possess the greatest extent of binding energy shift, implying the atomic charge displacement is the most significant at this condition, which would effectively alter the electronic structure of Pd and further influence the Pd‐H 2 interactions. Different from Pd and O, the intensity of the Au (111) XRD peak remains unchanged during the whole process.…”

“…Finally, the PdO-PdAu HSs were obtained by reduction of PdO-Au HSs in NaBH 4 solution for certain degree via controlling the reaction time. [21,25] A detailed characterization of samples obtained during each synthesize step can be found in Figures S1 and S2, Supporting Information.…”

“…[ 9 ] In the present work, PdO‐decorated PdAu ternary materials with hollow shell structure (named as PdO‐PdAu HSs) are synthesized by a simple NaBH 4 ‐reduction process. [ 21 ] PdO‐PdAu HSs have shown admirable H 2 ‐sensing performance with ultrafast room‐temperature response in air background. The hollow shell structure of the proposed PdO‐PdAu HSs materials ensures the high surface area/volume ratio and high H 2 accessibility, and the introduction of Au and PdO forming Au/Pd and PdO/Pd interfaces that effectively enhance the H 2 absorption ability of Pd.…”

“…[9] In the present work, PdO-decorated PdAu ternary materials with hollow shell structure (named as PdO-PdAu HSs) are synthesized by a simple NaBH 4 -reduction process. [21] PdO-PdAu HSs have shown admirable H 2 -sensing performance with ultrafast room-temperature Designing ultrafast H 2 sensors is of particular importance for practical applications of hydrogen energy but still quite challenging. Herein, PdO decorated PdAu ternary hollow shells (PdO-PdAu HSs) exhibiting an ultrafast response of ≈0.9 s to 1% H 2 in air at room temperature are presented.…”