Heteroatom‐Modulated Switching of Photocatalytic Hydrogen and Oxygen Evolution Preferences of Anatase TiO₂ Microspheres

Abstract

Understanding and manipulating the two half‐reactions of photoinduced electron reduction and hole oxidation are key to designing and constructing efficient photocatalysts. Here, how the spatial distribution of the heteroatom modulates photocatalytic reduction (hydrogen evolution) and oxidation (oxygen evolution) reaction preferences is investigated by moving boron from the core to the shell of an anatase TiO2 microsphere along [001] via thermal diffusion control. The preference towards photocatalytic hydrogen and oxygen producing reactions from splitting water can be switched by creating a shell with an interstitial Bσ+ (σ ≤ 3) gradient in the TiO2 microsphere. This switching stems from the downward shift of electronic band edges of the shell by a band bending effect that originates from the extra electrons coming from the interstitial Bσ+. These results create new opportunities for designing and constructing efficient photocatalysts by spatial heteroatom engineering.

Microsphere assembly of boron-doped Rutile TiO2 nanotubes with enhanced photoelectric performance

“…Therefore, the unchanged band gap in our study may arise from the simultaneous behaviors of boron atom in TiO 2 . However, the similar result has been observed by Liu et al [30], who insisted that the intrinsic band gap of TiO 2 is independent of the chemical states of boron. The identical value of 2.99 eV is calculated based on the UV-visible diffuse reflectance data, which is approximate to the theoretical energy gap of rutile TiO 2 .…”

Maximizing the visible light photoelectrochemical activity of B/N-doped anatase TiO2 microspheres with exposed dominant {001} facets

“…Additional N-doping did not change the basic shape of the microspheres. However, compared to the sharp edges of the square {001} facets of the pristine boron-doped TiO 2 microspheres [27], the edges of those further doped with N were less defined as a result of the nitrogen diffusion from the surface to the bulk. A high resolution TEM image (Fig.…”

“…Interstitial boron-doped TiO 2 microspheres (around 95 wt% anatase and 5 wt% rutile) were prepared by the acid hydrolysis of a TiB 2 precursor according to a reported procedure [27]. The details for nitrogen doping is described in the Supplementary information.…”

WB crystals with oxidized surface as counter electrode in dye-sensitized solar cells

“…Owing to their unique physicochemical properties, metal borides traditionally as an important class of structural ceramics have shown their additional potential in both functional applications [33] and synthesizing corresponding metal oxides or metal oxide/boride heterostructures when used as precursors [36][37][38][39]. Despite the high chemical stability of most metal boride crystals, their surfaces are prone to be oxidized spontaneously when exposed to air even at room temperature.…”