energies Article Au Coated Printed Circuit Board Current Collectors Using a Pulse Electroplating Method for Fuel Cell Applications Sang-Sun Park 1,2 , Na-Young Shin 2 , Chanmin Lee 3 , Yukwon Jeon 4, *, Won Seok Chi 5,6, * and Yong-Gun Shul 2, *   Citation: Park, S.-S.; Shin, N.-Y.; Lee, C.; Jeon, Y.; Chi, W.S.; Shul, Y.-G. Au Coated Printed Circuit Board Current Collectors Using a Pulse Electroplating Method for Fuel Cell Applications. Energies 2021, 14, 4960. https://doi.org/10.3390/en14164960 Academic Editor: Antonino S. Aricò Received: 1 June 2021 Accepted: 10 August 2021 Published: 13 August 2021 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). 1 LOTTE Chemical, #24-1, Jang-dong, Yuseong-gu, Daejeon 305-726, Korea; sangsunpark@lotte.net 2 Department of Chemical and Biomolecular Engineering, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul 03722, Korea; sky820906@hanmail.net 3 Research Institute of Clean Manufacturing System, Green and Sustainable Materials R&D Department, Korea Institute of Industrial Technology, 89 Yangdaegiro-gil, lpjang-myeon, Seobuk-gu, Cheonan-si 31056, Korea; clee@kitech.re.kr 4 Department of Environmental and Energy Engineering, Yonsei University, 1 Yonseidae-gil, Wonju 26493, Korea 5 Department of Polymer Engineering, Graduate School, Chonnam National University, 77 Yongbong-ro, Buk-gu, Gwangju 61186, Korea 6 School of Polymer Science and Engineering, Chonnam National University, 77 Yongbong-ro, Buk-gu, Gwangju 61186, Korea * Correspondence: ykjeon@yonsei.ac.kr (Y.J.); wschi@jnu.ac.kr (W.S.C.); shulyg@yonsei.ac.kr (Y.-G.S.); Tel.: +82-33-760-2466 (Y.J.); +82-62-530-1875 (W.S.C.); +82-2-2123-2758 (Y.-G.S.) Abstract: The effect of the Au coated printed circuit board (PCB) as a current collector on the perfor- mance of fuel cells is demonstrated. In this study, optimized pulse electroplating was introduced, which was found to be much more effective compared to the direct current (DC) plating for the PCB fabrication based on the passive area from the potentiodynamic polarization scan. Variable electrochemical parameters such as applied potential and frequency for the pulse electroplating method are controlled. Using the polarization tests, the corrosion behavior of the Au coated PCB layer was also observed. From these basic data, the coating methods and electrochemical parameters were systematically controlled to achieve efficient results for direct methanol fuel cells (DMFCs). The stability test for the cell operation indicates that the micro DMFC with the Au coated PCB substrate formed at a frequency of 10 Hz exhibited the highest stability and performance. As a result, the Au coated PCB substrate using pulse electroplating at 1.5 V and 1 kHz can be a promising current collector for portable DMFCs. Keywords: pulse electroplating; printed circuit board (PCB); current collector; corrosion; fuel cells 1. Introduction Fuel cells have attracted significant attention because it uses fuel (i.e., hydrogen) and an oxidizing agent (i.e., oxygen) to convert the chemical energy to electrical energy, thereby gaining remarkable attention as one of the potential energy devices [1,2]. Direct methanol fuel cells (DMFCs), which are a class of fuel cells, are of practical interest due to the convenience of their fuel to employ in portable applications [3]. However, they have not yet satisfied the requirements of entering the commercial market, which can be attributed to its a relatively low power density and stability compared with conventional portable power supply systems [4]. Despite the drawbacks of DMFCs, micro DMFCs are still attractive for portable applications because they can significantly reduce the size [5]. In particular, the current collector is one of the key factors to not only obtain a high efficiency, but also minimize the size of the DMFC [6]. Traditional current collectors such as graphite and stainless steel are not appropriate candidates for small DMFCs because of their restrictions in terms of flexibility. Energies 2021, 14, 4960. https://doi.org/10.3390/en14164960 https://www.mdpi.com/journal/energies