This article has been accepted for publication and undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process, which may lead to differences between this version and the Version of Record . Please cite this article as doi: 10.1002/ente.201900603 This article is protected by copyright. All rights reserved Layer-by-Layer coating of Cobalt-based Ink for Large-Scale Fabrication of OER Electrocatalyst Ajay B. Urgunde, Vipin Kamboj, # Hamid P. K # ., and Ritu Gupta* Department of Chemistry, Indian Institute of Technology Jodhpur, Karwar, Rajasthan-342037, India E-mail: (ritu@iitj.ac.in) # These authors contributed equally Keywords: cobalt oxide, carbon cloth, layer-by-layer, oxygen evolution reaction, stability Abstract The scalablity and stability of an electrocatalyst is one of the biggest challenge for their practical applicablity. In this context, Co 3 O 4 nanoparticles conformally coated on a light weight, 3D and highly conducting carbon cloth is fabricated using an easily synthesized cobalt hexadecylthiolate complex as ink. This method is especially useful for large-scale production as the complex can be synthesized in large quantities and coated on 3D substrates by simple dip-coating method. The optimum loading of the catalyst is achieved through a Layer-by-layer (LbL) assembly of cobalt hexadecylthiolate complex via repeated dip-coating of carbon cloth electrode in the solution. The Co 3 O 4 /CC undergoes electrochemical oxidation and converts to CoOOH as active species and act as a highly efficient electrocatalyst with optimized loading. The Co 3 O 4 -16/CC with sixteen times dip coating exhibits remarkable stability over 24 hours with an overpotential of 300 mV at 10 mA/cm 2 and Tafel slope of 77.06 mV/dec. The high catalytic activity towards oxygen evolution reaction (OER) in 1 M KOH due to the LbL coating is better than conventional Co 3 O 4 and comparable to IrO 2 and RuO 2 electrocatalyst with a future possibility of commercial-scale production at lower cost. ritu@iitj.ac.in @iitj.ac uthors contrib ors cont s: s: cobalt oxid cobalt ox ablity and sta lity and applicablity. plicabli 3D and highl 3D and hig xadecylthiola decylthi n as the com as the co e dip e dip- -coating coati - layer yer (LbL) LbL Acce cloth electro oth elec erts to CoOO s to Co d loading oading. Th . over 24 hour er 24 ho V/dec. The V/dec. T hi e to the LbL Lb