Ultrasound-Driven Defect Engineering in TiO_2–x Nanotubes─Toward Highly Efficient Platinum Single Atom-Enhanced Photocatalytic Water Splitting

Abstract

Single-atom catalysts (SACs) have demonstrated superior catalytic activity and selectivity compared to nanoparticle catalysts due to their high reactivity and atom efficiency. However, stabilizing SACs within hosting substrates and their controllable loading preventing single atom clustering remain the key challenges in this field. Moreover, the direct comparison of (co-) catalytic effect of single atoms vs nanoparticles is still highly challenging. Here, we present a novel ultrasound-driven strategy for stabilizing Pt single-atomic sites over highly ordered TiO 2 nanotubes. This controllable low-temperature defect engineering enables entrapment of platinum single atoms and controlling their content through the reaction time of consequent chemical impregnation. The novel methodology enables achieving nearly 50 times higher normalized hydrogen evolution compared to pristine titania nanotubes. Moreover, the developed procedure allows the decoration of titania also with ultrasmall nanoparticles through a longer impregnation time of the substrate in a very dilute hexachloroplatinic acid solution. The comparison shows a 10 times higher normalized hydrogen production of platinum single atoms compared to nanoparticles. The mechanistic study shows that the novel approach creates homogeneously distributed defects, such as oxygen vacancies and Ti 3+ species, which effectively trap and stabilize Pt 2+ and Pt 4+ single atoms. The optimized platinum singleatom photocatalyst shows excellent performance of photocatalytic water splitting and hydrogen evolution under one sun solarsimulated light, with TOF values being one order of magnitude higher compared to those of traditional thermal reduction-based methods. The single-atom engineering based on the creation of ultrasound-triggered chemical traps provides a pathway for controllable assembling stable and highly active single-atomic site catalysts on metal oxide support layers.

Dual-defected pine-needle W18O49–TiO2(R)–TiO2(A) heterojunctions for the complete elimination of naphthalene

“…It is surprising to find an evident peak for the WTNWs-2 sample, indicating a further increase in the surface oxygen vacancy concentration than that of the pure TNWs sample. 42,43 Combined with the XPS and ESR results, it can be speculated that the prepared heterojunction sample can provide more capture points for photogenerated carriers so as to inhibit the rapid recombination between the electron-hole pairs, promote electron transfer and improve the photocatalytic activity. 44 3.1.3 Morphological analysis.…”

A review on the recent advances in the design and structure–activity relationship of TiO2-based photocatalysts for solar hydrogen production

“…Noble metals including Ru, 79 Rh, 80 Pd, 44,48,81 Au, 49,82–84 Ag, 85–87 and Pt 50,88–90 are widely used as a co-catalyst with TiO 2 in photocatalytic hydrogen production due to their unique properties such as formation of a Schottky barrier, 43,91 efficient interfacial electron transfer, photostability, ability to show surface plasmon resonance, 92 formation of impurity energy levels, 79 and oxygen vacancies. 80 There are two types of noble metals, plasmonic (Ag and Au) and non-plasmonic (Pt, Pd, Ru, and Rh).…”

Promoting water-splitting reaction on TiO2/gCN with Pd/SrO cocatalysts: H2 evolution in the absence of a sacrificial reagent

“…30 TiO 2 is a highly efficient photocatalyst that is commonly used due to its affordability, suitable electrical/optical properties, durability and hydrophilic nature. 31,32 Due to its high energy bandgap, the activation of TiO 2 is limited to the UV region, which represents only 4% of sunlight. Several methodologies have been developed to address this challenge, e.g.…”

“…30 TiO 2 is a highly efficient photocatalyst that is commonly used due to its affordability, suitable electrical/optical properties, durability and hydrophilic nature. 31,32 Due to its high energy bandgap, the activation of TiO 2 is limited to the UV region, which represents only 4% of sunlight. Several methodologies have been developed to address this challenge, e.g., metal oxide coating, 33 manufacturing of core-shell microspheres, 34 neutral network construction, 35 layering visible spectrum active photosensitizers, 36 and fabrication of heterostructures.…”