Binder free cobalt iron phosphate thin films as efficient electrocatalysts for overall water splitting Suraj A. Khalate a , Sujit A. Kadam b , Yuan-Ron Ma b , Sachin B. Kulkarni c , Vinayak G. Parale d , Umakant M. Patil a,⇑ a Centre for Interdisciplinary Research (CIR), D. Y. Patil Education Society, Kolhapur-416006, India b Department of Physics, National Dong Hwa University, Hualien-97401, Taiwan c Department of Physics, Tuljaram Chaturchand College, Baramati-413102, India d Department of Materials Science and Engineering, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul-03722, Republic of Korea graphical abstract article info Article history: Received 12 October 2021 Revised 22 December 2021 Accepted 3 January 2022 Available online 12 January 2022 Keywords: Composition Hydrothermal synthesis Morphological evolution Overall water splitting Synergistic effect abstract Designing nanostructure based robust catalyst for the electrochemical water splitting is the great task in the energy conversion field to accomplish high electrical conductivity, low overpotential and long lasting activity. Herein, the electrochemical overall water splitting is reported by using the hydrothermally syn- thesized binder free cobalt iron phosphate thin films on low cost stainless steel substrates as a conduct- ing backbone for the first time. The effect of composition ratio variation of cobalt and iron was studied on the structural, compositional, morphological, and surface electronic properties by conducting various characterizations which results in amorphous hydrous cobalt iron phosphate having mesoporosity. The as synthesized cobalt iron phosphate having composition ratio (50:50 of Co:Fe) exhibits excellent elec- trochemical OER and HER catalytic water splitting performance. Best performing electrode exhibits smallest overpotentials of 251.9 mV and 55.5 mV for OER and HER respectively at 10 mA/cm 2 current density. To split water molecule into the H 2 and O 2 by overall water splitting in same alkaline medium, https://doi.org/10.1016/j.jcis.2022.01.015 0021-9797/Ó 2022 Elsevier Inc. All rights reserved. ⇑ Corresponding author. E-mail address: umakant.physics84@gmail.com (U.M. Patil). Journal of Colloid and Interface Science 613 (2022) 720–732 Contents lists available at ScienceDirect Journal of Colloid and Interface Science journal homepage: www.elsevier.com/locate/jcis