Contents lists available at ScienceDirect Solar Energy Materials and Solar Cells journal homepage: www.elsevier.com/locate/solmat Solar light driven photoelectrocatalytic hydrogen evolution and dye degradation by metal-free few-layer MoS 2 nanoflower/TiO 2 (B) nanobelts heterostructure Kamal Kumar Paul a , N. Sreekanth b , Ravi K. Biroju b,1 , Tharangattu N. Narayanan b , P.K. Giri a,c, ⁎ a Department of Physics, Indian Institute of Technology Guwahati, Guwahati 781039, India b Tata Institute of Fundamental Research - Hyderabad, Sy. No. 36/P, Gopanapally Village, Serilingampally Mandal, Hyderabad 500107, India c Centre for Nanotechnology, Indian Institute of Technology Guwahati, Guwahati 781039, India ARTICLE INFO Keywords: MoS 2 /TiO 2 nanobelt Heterostructure Photocatalysis Dye degradation Photoelectrocatalysis Hydrogen evolution reaction ABSTRACT A rational design of metal-free hierarchical nanostructures is critical for achieving next-generation photo- catalytic system. Transition metal dichalcogenide, e.g., MoS 2 based heterostructures (HSs) with shape-controlled TiO 2 have attracted great attention in visible light electrocatalysis owing to their unique crystal structure, morphology and chemical properties. Herein, we demonstrate a low temperature solvothermal growth of few layer MoS 2 nanoflowers (NFs) over the porous TiO 2 (B) nanobelts (NBs) for enhanced hydrogen evolution re- action (HER) in acidic media as well as improved photocatalytic degradation of organic dye rhodamine-B (RhB) under visible light. Few-layer MoS 2 NFs with lateral sizes 130–350 nm were successfully grown on TiO 2 NBs, as revealed from the high resolution TEM imaging. EDS mapping confirms the elemental composition and their spatial distribution in the HS sample. MoS 2 /TiO 2 NBs HS exhibits extremely high adsorption ability (66% after 40 min) under dark as well as enhanced photocatalytic degradation efficiency (80% after 60 min) of RhB under visible light irradiation. A systematic photoelectrochemical measurements demonstrate that the MoS 2 /TiO 2 NBs HS exhibits excellent HER activity in acidic electrolyte with an overpotential and estimated Tafel slope to be -320 mV at 10 mA/cm 2 and 95 mV/dec, respectively, which is much lower than that of the pristine TiO 2 NBs measured to be -792 mV and 135 mV/dec, respectively, under visible light. It is shown that the Volmer- Heyrovsky mechanism leads to the extremely high hydrogen generation at the working electrode made with edge-defect enriched few layer MoS 2 on porous TiO 2 NBs. 1. Introduction Ever increasing energy crisis and environmental pollution have necessitated the research efforts on the development of pollution free energy sources and practical solution to the everyday pollutions to the environment. Hydrogen is believed to be one of the most promising alternatives to fossil fuels and a source of renewable green energy having potential ability to replace the conventional energy sources in future. Solar light driven photocatalysis using semiconductor hetero- structures (HSs) is one of the most promising green technologies for the generation of hydrogen by water splitting as well as remediation of environmental pollution [1–3]. After the pioneering work by Fujishima and Honda on the water splitting at the TiO 2 electrode in an electro- chemical cell under the irradiation of UV light, hydrogen production using photoelectrocatalytic method by solar energy harvesting has become a clean, economical and environment friendly approach [4]. Simultaneously TiO 2 and TiO 2 based nanostructures are being used for the decontamination of toxic and hazardous organic pollutants for the environmental protection [5–12]. To make the system commercially viable, the photocatalyst should be solar light active and efficient en- ough with high stability. To broaden the light harvesting window from UV to visible/NIR and uplift the catalytic activity, numerous strategies have been explored including impurity doping [13–15], staggered type HSs [1,5,16] and TiO 2 based plasmonic HSs with noble metal nano- particles (NPs) [17–20] etc. Carbon nanotube coated with Cu 2 O [21], Fe-Pd alloy [22] can be a good photocatalyst. Synthesis of Fe 3 O 4 / polyaniline by self-assembly approach, cobalt-based mixed oxide na- nocrystals, edge-enriched graphene quantum dots and various core- shell nanostructures have recently been introduced for the efficient photocatalytic dye degradation, heavy metal removal, water oxidation https://doi.org/10.1016/j.solmat.2018.05.056 Received 30 October 2017; Received in revised form 3 April 2018; Accepted 28 May 2018 ⁎ Corresponding author at: Department of Physics, Indian Institute of Technology Guwahati, Guwahati 781039, India. 1 Present address: Nanoscale Physics Research Laboratory, School of Physics and Astronomy, University of Birmingham, Birmingham B15 2TT, United Kingdom. E-mail address: giri@iitg.ernet.in (P.K. Giri). Solar Energy Materials and Solar Cells 185 (2018) 364–374 0927-0248/ © 2018 Elsevier B.V. All rights reserved. T