Harvesting, Storing and Utilising Solar Energy using MoO₃: Modulating Structural Distortion through pH Adjustment

Abstract

Nanostructured molybdenum oxide (α‐MoO3) thin film photoelectrodes were synthesised by anodisation. Upon band gap‐excitation by light illumination, α‐MoO3 is able to store a portion of the excited charges in its layered structure with the simultaneous intercalation of alkali cations. The stored electrons can be discharged from α‐MoO3 for utilisation under dark conditions, and α‐MoO3 is able to recharge itself with successive illuminations to behave as a ‘self‐photo‐rechargeable’ alkali‐ion battery. The alteration of the anodisation pH allowed the crystal structure and oxygen vacancy concentrations of α‐MoO3 to be modulated to achieve (i) a distorted MoO6 octahedra for enhanced charge separation and storage, (ii) a layered structure with a greater exposed (010) crystal face for rich and reversible ion intercalation and (iii) a highly crystalline thin film that suppresses electron–hole pair recombination. Overall, the larger MoO6 octahedral distortion in α‐MoO3 at a higher pH favours charge storage, whereas smaller octahedral distortion at a lower pH leads to anodic photocurrent enhancement.

Formation of intrinsic and silicon defects in MoO3 under varied oxygen partial pressure and temperature conditions: an ab initio DFT investigation

“…The worldwide search for efficient and cost-effective energy conversion and storage systems has resulted in the investigation of new uses for lesser known materials. Molybdenum trioxide and its sub-stoichiometric form (MoO 3Àx ; 0 < x < 1) is a material with proposed applications in batteries, [1][2][3] electrochemical capacitors, [4][5][6][7][8] sensors, 9,10 catalysis, [11][12][13] photo-catalysis, 14,15 electrochromism and photochromism. [16][17][18] It has also been found to be an effective hole transport layer in semiconductor devices [19][20][21] and a range of photovoltaic cells.…”

Influence of MoO3(110) Crystalline Plane on Its Self-Charging Photoelectrochemical Properties

“…TiO 2 or dye); (ii) the requirement of multi-component, hybrid photoelectrode composites; and (iii) the limited efficiency arising from the possible electron losses during the charge transfer process. To overcome the above limitations, our group has recently reported the self-photo-recharge ability of WO 3 12 13 and MoO 3 14 photocatalysts as illustrated in Figure 1 (for MoO 3 ). Both WO 3 and MoO 3 photocatalysts are distinguished from traditional photocatalysts by their ability to also act as an advanced energy storage material.…”

An Operando Mechanistic Evaluation of a Solar‐Rechargeable Sodium‐Ion Intercalation Battery

“…Figure 2b shows the unit cell of α-MoO 3 along the ab plane and three crystallographically distinct O sites present in the distorted MoO 6 octahedra. [16,24] Rietveld refinement of the α-MoO 3 structural model with the XRD pattern (Figure 2c The structure of the Na x MoO 3 phase was modelled using α-MoO 3 with XRD pattern (C), resulting in refined lattice parameters of a = 4.0702(4), b = 14.157 (7), and c = 3.808(2) Å, fits in Figure S4 (Supporting Information), details in Table S1 (Supporting Information). Foreign ions with a small radius such as H + , Li + , and Na + can be accommodated in the inter-and intralayer sites of the structure.…”

“…The photointercalation reaction at the electrode surface can be represented by Equation (1 where, TX 2 and TM int X 2 are nonintercalated and intercalated transition metal dichalcogenides, respectively; e − (hν) and h + (hν) are photogenerated electrons and holes; and M + solv represents the ionic species in the electrolyte which are to be intercalated. [14][15][16][17] These oxides are n-type semiconductors possessing favorable valence band potentials for oxygen evolution from water. [3][4][5][6][7] The experiments were preliminary in nature and designed to screen a wide range of potential semiconductor host compounds for solar-intercalation batteries.…”