Materials Letters 350 (2023) 134936 Available online 25 July 2023 0167-577X/© 2023 Elsevier B.V. All rights reserved. Nickel molybdate nanorods synthesized on carbon cloth as an electrocatalyst for methanol oxidation and hydrogen evolution reactions Dinesh Muthu , T. Sadhasivam * , Tae Hwan Oh * School of Chemical Engineering, Yeungnam University, Gyeongsan, Gyeongbuk 712-749, Republic of Korea A R T I C L E INFO Keywords: NiMoO 4 Electrocatalyst Methanol oxidation reaction HER ABSTRACT In this report, the nickel molybdate (NiMoO 4 ) nanorods were grown on carbon cloth (CC) with an average length of 3 µm and a diameter of 130 nm. The NiMoO 4 /CC demonstrated a lower onset potential of 0.553 V vs. Hg/HgO at 10 mA/cm 2 for methanol oxidation reaction (MOR). In addition, the electrocatalyst showed notable cyclic stability, where the onset potential attained 0.585 and 0.616 V vs. Hg/HgO at 10 mA/cm 2 during the 250 th and 1000 th cycles, respectively. In the hydrogen evolution reaction (HER), the NiMoO 4 /CC exhibited good perfor- mance with an overpotential of 0.517 V vs. RHE at 10 mA/cm 2 , the Tafel slope of 144 mV/dec, and a turnover frequency of 1.298H 2 /active site. The higher active sites (2.594 × 10 17 cm 2 ) and high electrochemical surface area (94.63 cm 2 ) of NiMoO 4 /CC electrocatalyst exhibited stable and effcient MOR and HER performances. 1. Introduction Hydrogen and methanol are excellent fuels for fuel cell technologies because of their high energy density and reliability. Direct methanol fuel cells are widely considered because of their easy availability, storage, high energy density, low cost, and safety. However, the sluggish meth- anol oxidation process and the formation of CO intermitted on the catalyst layer limit its benefts. The impact of hydrogen production in a greener way by water electrolysis leads to zero carbon emission. In a proton exchange membrane fuel cell, methanol oxidation occurs on the anode side, and the produced proton is used to generate hydrogen on the cathode side. Commonly, the platinum group metals and their com- pounds/alloys/composites have been proven as excellent and key elec- trocatalysts for methanol oxidation reaction(MOR) and hydrogen evolution reaction(HER) [1]. Though, its rarity, high production cost, and certain stability-related issues are the main drawbacks of platinum- based catalysts. To replace these electrocatalysts, binary metal oxides have been considered alternatives and exhibited excellent catalytic performances because of their different oxidation states, low charge transfer resistance, and abundant active sites. In this viewpoint, molybdate-based compounds, specifcally AMoO 4 (A-Ni, Mn, Sn, Bi, Fe, etc.), are considered excellent catalysts in different electrochemical sectors because of their structural integrity [2]. In this report, the NiMoO 4 nanorods grown on carbon cloth (CC) demonstrated as an effective electrocatalyst for MOR and HER in a three-electrode system. 2. Experimental section Typically, 168 g of nickel nitrate was dissolved in 40 mL of DI water. Then, 0.96 g of sodium molybdate in 40 mL of DI water was added. The mixture was transferred into Tefon vessel containing CC. The hydro- thermal reaction was carried out at 190℃ for 12 h. The NiMoO 4 precursor-grown CC (1 × 1 cm) was placed in a muffe furnace at 350℃ for 1.5 h. The amount of NiMoO 4 loaded onto the CC was ~2 mg. The synthesis and electrocatalytic activity of NiMoO 4 /CC is depicted in Fig. 1. 3. Results and discussion As shown in Fig. 2a, the XRD peaks at 13.52 ◦ (0 0 1), 29.86 ◦ ( 311), 34.02 ◦ ( 131), 37.04 ◦ ( 113), 40.28 ◦ ( 313), 47.61 ◦ ( 204), 53.36 ◦ (150), 59.86 ◦ (4 4 0) and 63.11 ◦ ( 621) and their planes confrmed the formation of monoclinic crystal structure (JCPDS card: 86-0361) of NiMoO 4 . In addition, two broad peaks (25.62 and 43.39 ◦ ) were observed corre- sponding to the CC. The Raman spectrum of the NiMoO 4 nanorods/CC is shown in Fig. 2b. The peaks at 364, 783, 876, 839, and 878 cm 1 belong to the bending vibration of Mo-O, asymmetrical stretching vibration of O-Ni, and asymmetrical stretching vibration of Ni-O-Mo, respectively [3]. Minor peaks at ~1353 and ~1606 cm 1 correspond to the D and G bands of CC. The XPS survey spectrum (Fig. 2c) confrmed the presence of Ni, O, and Mo in the NiMoO 4 and its elemental compositions were * Corresponding authors. E-mail addresses: sadhasivam.nano@yu.ac.kr (T. Sadhasivam), taehwanoh@ynu.ac.kr (T.H. Oh). Contents lists available at ScienceDirect Materials Letters journal homepage: www.elsevier.com/locate/matlet https://doi.org/10.1016/j.matlet.2023.134936 Received 26 April 2023; Received in revised form 18 July 2023; Accepted 20 July 2023