This journal is © The Royal Society of Chemistry 2022 Chem. Commun., 2022, 58, 3689–3692 | 3689 Cite this: Chem. Commun., 2022, 58, 3689 Concerted effect of Ni-in and S-out on ReS 2 nanostructures towards high-efficiency oxygen evolution reaction† Tapas K. Das, a Tapan Ping, ab Manoj Mohapatra, cd Shahid Anwar, a Chinnakonda S. Gopinath e and Bikash Kumar Jena * ab Herein, a one-step hydrothermal reaction is developed to synthe- size a Ni-doped ReS 2 nanostructure with sulphur defects. The material exhibited excellent OER activity with a current density of 10 mA cm À2 at an overpotential of 270 mV, a low Tafel slope of 31 mV dec À1 , and good long-term durability of 10 h in 1 M KOH. It shows high faradaic efficiency of 96%, benefiting from the rapid charge transfer caused by the concerted effect of Ni-in and S-out on the ReS 2 nanostructure. Hydrogen has received significant attention to boost green and sustainable energy growth as an alternative to fossil fuels and the associated severe environmental pollution problems. 1–3 Water electrolysis is considered promising, eco-friendly, and one of the best ways to produce hydrogen. It has two comple- mentary half-reactions, i.e., the hydrogen evolution reaction (HER) at the cathode and the oxygen evolution reaction (OER) at the anode. However, the efficiency of the overall water splitting process gets circumscribed by the sluggish kinetics of the OER, it being a complicated multistep four-electron transfer process. 3–5 Therefore, catalysts are needed to increase the reaction rate and lower the overpotentials towards the OER. Ru and Ir-based materials are currently the benchmark cata- lysts for the OER, but their shortage and high-cost limit their commercialization and industrial production. 6,7 So, it is neces- sary to develop an electrocatalyst of abundant elements with high activity and durability with low cost. Recently, earth abundant transition metal di-chalcogenide (TMD) com- pounds have attracted tremendous attention due to their cost-effectiveness and outstanding ability toward catalytic HER and OER activity. 8 TMDs such as ReX 2 (X = S, Se) have emerged and received great attention due to their surprising structural, electrical, optical, and chemical properties. Generally, TMDs are stabi- lized in a highly symmetric 2H structure, but ReX 2 is a distorted trigonal 1T phase system with shrunk in-plane crystal symmetry. 9 Several 2D TMDs have been constructed by doping, alloying, heteroatom incorporation, and vacancy creation as a blueprint for better electrolytic performance. Similar to other 2D TMDs, the catalytic activity of ReS 2 also comes from the edge sites, whereas the basal planes have very poor activity. So stimulating the basal planes would be a promising approach for increasing the catalytic activity of the ReS 2 -based materials. Recent theoretical studies have suggested that doping of transi- tion metals on 1T 0 ReS 2 can increase the active sites on the basal planes. 10,11 Recently, a few reports have revealed the intrinsic HER activity of ReS 2 -based materials. However, the OER properties of the ReS 2 structure have not been explored thoroughly. This report portrays the synthesis of Ni-doped and S-vacancy ReS 2 nanostructures by hydrothermal and wet chemical methods. A study of the concerted effect of Ni-in and S-out on the ReS 2 nanostructures towards the OER is performed (Fig. 1). Here, Ni doping at different percentages with S vacancies at different durations on ReS 2 nanostructures has been optimized and used for OER applications. The mate- rial with 5% Ni doping and S vacancies is referred to as Ni d (5)S v @ReS 2 NS. Fig. S1 (ESI†) shows the X-ray diffraction (XRD) pattern of the Ni d (5)S v @ReS 2 NS material. It shows five peaks located at 2y values of 14.041, 21.421, 32.881, 46.71, and 57.791, corresponding to the (100), (101), (002), (1 % 13) and ( % 122) diffractions of the distorted triclinic ReS 2 (JCPDF No. 82- 1379). 12 Fig. S2 (ESI†) shows the SEM image of the Ni d (5)S v @ReS 2 NS material. It consists of a hierarchical struc- ture assembled from many nanosheet ReS 2 layered structures. From the elemental color mapping, it is inferred that Re, S, and Ni are evenly distributed over the whole samples (Fig. S2, ESI†). The high-resolution transmission electron microscope (HR-TEM) a Materials Chemistry Department, CSIR-Institute of Minerals and Materials Technology, Bhubaneswar, Odisha, 751013, India. E-mail: bikash@immt.res.in b Academy of Scientific & Innovative Research, Ghaziabad, 201002, India c Radiochemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai, 400085, India d Homi Bhabha National Institute, Anushakti Nagar, Mumbai, 400094, India e Catalysis and Inorganic Chemistry Division, CSIR-National Chemical Laboratory, Dr Homi Bhabha Road, Pune, 411008, India † Electronic supplementary information (ESI) available: Experimental details, characterization and electrochemical analysis. See DOI: 10.1039/d1cc07030d Received 14th December 2021, Accepted 7th February 2022 DOI: 10.1039/d1cc07030d rsc.li/chemcomm ChemComm COMMUNICATION Published on 08 February 2022. Downloaded on 12/24/2023 12:02:51 PM. View Article Online View Journal | View Issue