Fabrication of Ni nanoclusters-modified brookite TiO2 quasi nanocubes and its photocatalytic hydrogen evolution performance

Abstract

The development of low-cost, earth-abundant and highly-efficient cocatalysts is still important to promote the photocatalytic H 2 evolution reaction over semiconductors. Herein, a series of Ni nanoclusters (NCs) modified brookite TiO 2 quasi nanocubes (BTN) (marked as Ni/BTN) are fabricated via a chemical reduction process. It is found that the loading content and oxidation state of Ni NCs can significantly influence the optical absorption, photocatalytic activity, and stability of Ni/BTN composites. Among the resultant Ni NCs-loaded products, 0.1%Ni/BTN composite delivers the best H 2 evolution activity (156 µmol/h), which is 4.3 times higher than that of the BTN alone (36 µmol/h). Furthermore, the Ni NCs with ultrafine size (∼2 nm) and high dispersity enable shorter charge transfer distance by quickly capturing the photoexcited electrons of BTN, and thus result in the improved activity even though the oxidization of some Ni NCs on BTN is harmful to the activity for H 2 evolution due to the much lower electron capturing capability of NiO than metallic Ni. This study not only clarifies that brookite TiO 2 would be a promising high-efficient photocatalyst for H 2 evolution, but also reveals vital clues for further improving its photocatalytic performance using low-cost Ni-based cocatalyst.

Recent progresses in photocatalytic hydrogen production: design and construction of Ni‐based cocatalysts

“…In contrast to the bulk Ni metal, the nano-scaled Ni species are more propitious to the efficient charge transfer and interface chemical reaction, which is attributed to an enlarged surface area and much more active sites. 60 The nickel nanoparticles with a size of ca. 10 nm could be introduced on CdS by a simple synthetic strategy.…”

“…This trait signifies that the Schottky junction also can be constructed between metallic Ni and semiconductor, and the junction is more beneficial for separation and migration of photo‐excited electrons and holes. In contrast to the bulk Ni metal, the nano‐scaled Ni species are more propitious to the efficient charge transfer and interface chemical reaction, which is attributed to an enlarged surface area and much more active sites 60 . The nickel nanoparticles with a size of ca.…”

Hydrothermal synthesis of Zn-doped brookite TiO2 for enhanced visible-light-responsive photocatalytic performance

“…Brookite TiO 2 photocatalyst has large band gap (3.1-3.4 eV) which responds only for a small fraction of solar spectrum, leading to low photocatalytic efficiency and poor absorption properties to visible light. To improve the performance of brookite TiO 2 photocatalyst, a great deal of work has been done to improve its photocatalytic activity, including synthesis of pure-phase brookite TiO 2 with different particle sizes or morphologies [15,[17][18][19][20], modification with foreign elements (e.g., cations, anions) [21][22][23][24], and combination with different semiconductor oxide materials, etc [25][26][27][28]. Modification with foreign elements has proven to be one of the most effective strategies to improve the photocatalytic activity of brookite TiO 2 .…”

“…Modification with foreign elements has proven to be one of the most effective strategies to improve the photocatalytic activity of brookite TiO 2 . Among the dopants, transition metals have been widely studied due to their unique oxidation state and chemical similarity with Ti, which can induce changes to the bandgap and defects in crystal structure of brookite TiO 2 [22][23][24]29]. Zeng et al [23] reported that the pohotocatalytic activity of brookite TiO 2 for H 2 production was improved significantly by introduction of Ni which offered shorter charge transfer distance by quickly capturing the photoexcited electrons of brookite TiO 2 .…”

Synthesis and Characterization of Sn/Ni Single Doped and Co–Doped Anatase/Rutile Mixed–Crystal Nanomaterials and Their Photocatalytic Performance under UV–Visible Light

“…The Sn 3d spectrum consists of two peaks at 486.1 eV and 494.6 eV, which are ascribed to Sn 3d 5/2 and Sn 3d 3/2 , indicating that Sn element exists as Sn 4+[35]. The peaks located at 855.7 eV and 861.8 eV correspond to Ni 2p 3/2 and the peaks located at 873.2 eV and 880.1 eV correspond to Ni 2p 1/2 , suggesting that Ni element exists in the form of +2 valence[14,40,41].…”