Submerged Photosynthesis of Molybdenum–Tungsten Nanostructures for Supercapacitor Application

Abstract

Research on electrochemical energy storage devices aims to produce supercapacitors via a facile and nonpolluting method. Because of unnecessary elemental doping and disordered morphologies of nano-oxides, impurities in raw materials during the conventional fabrication process would reduce the pseudocapacitance. Herein, we propose a submerged photosynthesis crystalline method for synthesizing oxygen vacancy (Vo)-enriched Mo–W oxide hydrates and Mo-doped tungsten oxide hydrate nanocomposites at 55 °C and normal pressure. In addition, this study describes the impact of Vos on pseudocapacitance using ab initio calculations based on density functional theory. Doping the WO3·0.33H2O lattice with Mo and Vos brings the conduction band closer to the Fermi energy level. The comparison of the ultraviolet–visible–near-infrared (UV–vis–NIR) irradiation spectrum and absorption coefficient calculation suggests that Mo and Vo doping is responsible for the NIR absorption. This study concludes that enriched Vos result in the highest specific capacitance and pseudocapacitive behavior of Mo x W1–x O3·0.33H2O.

Defect Driven Opto‐Critical Phases Tuned for All‐Solar Utilization

“…The result in Figure 2c is under scan rate of 5 mV s −1 . Beyond this, the CV profiles broadening was observed, regardless of under dark and visible conditions (Figure S9C,D, Figure S10, Supporting Information), indicative of diffusion‐controlled [ 14 ] in the Cu1%‐WO 3 ·H 2 O sample. Overall, these phenomena are consistent with the electrochromic reaction: WO 3 · H 2 O + x H + + xe − ↔H x WO 3 · H 2 O(0 ≤ x ≤ 1), as corroborated by the absorbance spectra.…”

“…The effect of hydrogen peroxide (H 2 O 2 ) on SPsC (see experimental section) of tungstic acid formation has been described comprehensively in our previous studies. [ 13,14 ] Figure 1c illustrates the growth mechanism of Cu‐doped WO 3 ·H 2 O, encompassing i) nucleation, ii) clustering, and iii) growth steps. In the presence of H 2 O 2 , ions resulting from oxidation of the W metals are formed: $$$$\begin{equation}{\rm{W + 3}}{{\rm{H}}}_{\rm{2}}{{\rm{O}}}_{\rm{2}}{\rm{ }} \to {\rm{WO}}_4^{2 - }{\rm{ + 2}}{{\rm{H}}}^{\rm{ + }}{\rm{ + 2}}{{\rm{H}}}_{\rm{2}}{\rm{O}}\end{equation}$$$$…”

“…Notably, the population density was found to escalate during Cu doping. Now, although the nuclei formation is underpinned by a combination of ·OH with the W anions ($$WO_4^{2 - }$$) (Equation ()), the SPsC for nanorods, [ 15,16 ] nanoflowers, [ 17 ] nanorice, [ 14 ] and heterostructures [ 18,19 ] growth has been generally related to occur in a characteristic manner, purportedly by “tip‐growth” mechanism. In this mechanism, V O rich region initially exhibits intense photo‐induced water splitting, followed by ·OH and OH − formation that generate the parent oxides.…”

“…In a bid to address this challenge, we have recently made significant strides in the system of tungsten‐oxide, leveraging the potential of metal‐doping via photo‐induced fabrication method, namely submerged photo‐synthesis of crystallites (SPsC). [ 13,14 ] Continuing in this vein, we have successfully fabricated Cu‐doped WO 3 ·H 2 O nanocrystallites, demonstrating an enhanced response across the entire solar wavelength spectrum. This achievement signifies a notable milestone in the field, underscoring the potential of harnessing the full spectrum of solar energy to augment energy utilization efficiency and pave the way for the development of advanced photonic devices and applications.…”

Submerged Photosynthesis of TiO2-CuO Hetero-nanoparticles for the Solar Photo-electrolysis of Multiple Environmental Hazardous Substances

“…So far, SPSC has proven to be useful in synthesizing a wide variety of metal oxides [31][32][33][34]. Furthermore, the SPSC method can be employed to fabricate metal oxide doping or heterojunctions for various applications [35][36][37].…”