Orbital Engineering in Sillén–Aurivillius Phase Bismuth Oxyiodide Photocatalysts through Interlayer Interactions

Abstract

Multicomponent inorganic compounds containing post-transition-metal cations such as Sn, Pb, and Bi are a promising class of photocatalysts, but their structure–property relationships remain difficult to decipher. Here, we report three novel bismuth-based layered oxyiodides, the Sillén–Aurivillius phase Bi4NbO8I, Bi5BaTi3O14I, and Bi6NbWO14I. We show that the interlayer Bi–Bi interaction is a key to controlling the electronic structure. The replacement of the halide layer from Cl to I negatively shifts not only the valence band but also the conduction band, thus providing lower electron affinity without sacrificing photoabsorption. The suppressed interlayer chemical interaction between the 6p orbitals of the Bi lone-pair cations reduces the conduction bandwidth. These oxyiodides have narrower band gaps and show much higher water oxidation activities under visible light than their chloride counterparts. The design strategy has not only provided three novel Bi-based photocatalysts for water splitting but also offers a pathway to control the optoelectronic properties of a wider class of lone-pair (ns2np0) semiconductors.

High Flux and Stability of Cationic Intercalation in Transition-Metal Oxides: Unleashing the Potential of Mn t2g Orbital via Enhanced π-Donation

“…According to the valence band theory, overlapping of the Mn-3d orbital with the 2p orbital of the ligand oxygen atom in MnO 6 forms both a bonding (Mn–O) and an antibonding (Mn–O)* band near the E F (Figure a) . The π* energy level is dominated by TM electrons when the linear combination energy level of the O 2p orbital is lower than those of TM nd xy , nd xz , and nd yz orbitals (E (2p) < E (ndt 2g )) …”

Combined Analyses on Electronic Structure and Molecular Orbitals of d10 Bimetal Oxide In2Ge2O7 and Photocatalytic Performances for Overall Water Splitting and CO2 Reduction

“…The development of sustainable energy and reducing the greenhouse gas in the atmosphere are the very hot topics at present to solve the emerging worldwide challenges of oil shortage and continual temperature increase. − Semiconducting photocatalysis is a plausible solution to both issues, i.e. photocatalytic overall water splitting into H 2 /O 2 , and photocatalytic reduction of CO 2 into CO, CH 4 or CH 3 OH. − Research in the field of heterogeneous photocatalysis include developing novel single-phase or composite photocatalysts, understanding the photocatalytic process, and elevating the quantum efficiency. − The hitherto single-phase photocatalysts capable of overall water splitting are still in a small number comparing to the composite ones, because they should satisfy not only the thermodynamics requirements for overall water splitting but also the kinetics requirements for two half reactions of H 2 /O 2 production. ,, The photodriven reduction of CO 2 involves the gas molecule adsorption and the reactions with multiple-electron transitions, either into CO or other products; thus the photocatalytic mechanism is quite complicated and people are still working on developing highly efficient photocatalysts. − …”

Probing the Polaronic Landscape in Bi4TaO8X Perovskite Oxyhalides Photocatalysts

“…After years of research, various materials such as perovskite oxynitrides (e.g., BaTaO 2 N and SrTaO 2 N) have been found to exhibit promising photoelectrochemical activity under visible light. − However, these materials are prone to self-oxidation during the reaction due to the oxidation of N 3– by the photogenerated holes. An alternative is the Sillén–Aurivillius perovskite oxyhalides Bi 4 TaO 8 X (X = Cl, Br), which exhibit high stability and efficiency under visible light. − These perovskite oxyhalides are characterized by the alternating stacking of Aurivillius perovskite blocks and Sillén blocks (see Figure ). According to density functional theory (DFT) studies, their valence band maximum (VBM) is mostly composed of O 2p orbitals rather than Xp orbitals, yet its position is much more negative than that of typical oxyhalides (BiOX) .…”