A sustainable molybdenum oxysulphide-cobalt phosphate photocatalyst for effectual solar-driven water splitting

Naseer Iqbal; Ibrahim Khan; Asghar Ali; Ahsanullhaq Qurashi

doi:10.1016/j.jare.2021.08.006

A sustainable molybdenum oxysulphide-cobalt phosphate photocatalyst for effectual solar-driven water splitting

J Adv Res. 2021 Aug 13:36:15-26. doi: 10.1016/j.jare.2021.08.006. eCollection 2022 Feb.

Authors

Naseer Iqbal¹, Ibrahim Khan², Asghar Ali¹, Ahsanullhaq Qurashi^{2

3}

Affiliations

¹ Department of Chemistry, College of Science, University of Hafr Al Batin, PO. Box 1803, Hafr Al Batin 31991, Saudi Arabia.
² Center of Research Excellence in Nanotechnology, King Fahd University of Petroleum and Minerals, Dhahran 31261, Saudi Arabia.
³ Department of Chemistry, Khalifa University of Science and Technology, Main Campus, Abu Dhabi, PO. Box 127788, United Arab Emirates.

Abstract

Introduction: Hydrogen is considered as a clean alternative green energy future fuel. Since the Honda-Fujishima effect for photoelectrochemical water splitting is known, there has been a substantial boost in this field. Numerous photocatalysts based on metals, semiconductors, and organic-inorganic hybrid-systems have been proposed. Several factors limit their efficiency, e.g., a stable PEC-WS setup, absorbing visible light, well-aligned band energy for charge transfer, electrons and holes, and their separation to avoid recombination and limited water redox reactions. Metallic doping and impregnation of stable and efficient co-catalysts such as Pt, Ag, and Au showed enhanced PEC-WS. We used Cobalt-based co-catalyst with molybdenum oxysulfide photocatalyst for effectual solar-driven water splitting.

Objectives: To develop photocatalysts for efficient PEC processes capable of absorbing sufficient visible light, good band energy for effective charge transfer, inexpensive, significant solar-to-chemical energy conversion efficiencies. Above all, it is developing such PEC-WS systems that will be commercially viable for renewable energy resources.

Methods: We prepared Molybdenum oxysulphide-cobalt phosphate photocatalyst for PEC-WS through a facile hydrothermal route using ammonium heptamolybdate, thiourea, and metallic Cobalt precursors.

Results: An effectual photocatalyst is produced for solar-driven water splitting. The conformal morphology of MoO_xS_y-CoPi nanoflowers is a significant feature, as observed under FE-SEM and HR-TEM. XRD confirmed the degree of purity and orthorhombic crystal structure of MoO_xS_y-CoPi. EDX and XPS identify the elemental compositions and corresponding oxidation states of each atom. A 2.44 eV band-gap energy is calculated for MoO_xS_y-CoPi from the diffused reflectance spectrum. Photo- Electrochemical Studies (PEC) under 1-SUN solar irradiation revealed 7-8 folds enhanced photocurrent (∼ 3.5 mA/cm2) generated from MoO_xS_y-CoPi/FTO in comparison to Co-PI/FTO (∼ 0.5 mA/cm2) and MoO_xS_y-/FTO respectively, within 0.5 M Na₂SO₄ electrolyte (@pH=7) and standard three electrodes electrochemical cell.

Conclusion: Our results showed MoO_xS_y-CoPi as promising photocatalyst material for improved solar-driven photoelectrochemical water splitting system.

Keywords: Hydrothermal Reaction Synthesis; MoOxSy-CoPi nanoflowers; Photocatalysis; Water Splitting.