(Digital Presentation) Durable Silica Nanosheets/Carbon Black Supported Catalyst for Proton Exchange Membrane Fuel Cells

Abstract

Proton exchange membrane fuel cells (PEMFCs) which have high efficiency have attracted attention as one of the most promising energy conversion devices. Currently the catalysts in PEMFCs are mainly carbon supported noble metals where the support can afford the electron transport environment to improve catalyst efficiency and decrease catalyst loss by strengthening catalyst–support bonding [1]. Due to high electrical conductivity and surface area, carbon-based catalyst supports are widely used in PEMFCs. However, the high electric fields applied to the fuel cell can easily cause carbon corrosion and further accelerate catalyst loss.New alternative support materials are needed to reduce costs and increase the lifetime of PEMFC electrodes. Recently, silica-based supports such as silicon oxide [2, 3] and silicon carbide [4] have been considered feasible as catalyst supports due to efficient catalyst utilization and their resistance to carbon corrosion. As a silica-based material, hydrophilic silica nanosheets (SN) derived from cheap natural vermiculite [5] is for the first time to be combined with carbon black (CB) as a catalyst support in this work. SN-CB supported platinum (Pt) catalysts were prepared according to different weight ratios of SN and CB using a modified polyol reduction method [6]. After 18000-cycle accelerated stress test (AST), as shown in Fig. 1a and b, the electrochemical surface area (ECSA) of Pt/SN2-CB3 (the weight ratio of SN to CB is 2: 3) decays from 23.7 to 22.5 m2/g (only 4.8% degradation) compared to Pt/CB (25.8% degradation from 16.0 to 11.9 m2/g). Meanwhile, Pt/SN2-CB3 shows comparable initial onset potential (0.850 V) and high half-wave potential (0.654 V) compared to 0.881 V onset potential and 0.625 V half-wave potential for Pt/CB as shown in Fig. 1c and d. The half-wave potential of Pt/SN2-CB3 after AST test demonstrated the addition of SN into the support can result in a stable oxygen reduction reaction (ORR) durability. The possible reason why the ECSA, ORR activity and durability of SN-CB supported platinum catalysts are enhanced is that the synergic interactions among carbon, silica nanosheets and Pt nanoparticles may hinder carbon corrosion, Pt agglomeration and dissolution [2]. Different weight ratios between SN and CB and the functionalized SNs are currently being tested and the real fuel cell data will be presented. Reference [1] Y.-J. Wang, D.P. Wilkinson, J. Zhang, Noncarbon support materials for polymer electrolyte membrane fuel cell electrocatalysts, Chemical reviews, 111 (2011) 7625-7651.[2] P. Dhanasekaran, A. Shukla, S.V. Selvaganesh, S. Mohan, S. Bhat, Silica-decorated carbon-Pt electrocatalyst synthesis via single-step polyol method for superior polymer electrolyte fuel cell performance, durability and stack operation under low relative humidity, Journal of Power Sources, 438 (2019) 226999.[3] P. Dhanasekaran, S.V. Selvaganesh, A. Rathishkumar, S. Bhat, Designing self-humidified platinum anchored silica decorated carbon electrocatalyst for boosting the durability and performance of polymer electrolyte fuel cell stack, International Journal of Hydrogen Energy, 46 (2021) 8143-8155.[4] L. Dong, J. Zang, J. Su, Y. Jia, Y. Wang, J. Lu, X. Xu, Oxidized carbon/nano-SiC supported platinum nanoparticles as highly stable electrocatalyst for oxygen reduction reaction, International journal of hydrogen energy, 39 (2014) 16310-16317.[5] Z. Guo, J. Chen, J.J. Byun, R. Cai, M. Perez-Page, M. Sahoo, Z. Ji, S.J. Haigh, S.M. Holmes, High-performance polymer electrolyte membranes incorporated with 2D silica nanosheets in high-temperature proton exchange membrane fuel cells, Journal of Energy Chemistry, 64 (2022) 323-334.[6] Z. Ji, M. Perez-Page, J. Chen, R.G. Rodriguez, R. Cai, S.J. Haigh, S.M. Holmes, A structured catalyst support combining electrochemically exfoliated graphene oxide and carbon black for enhanced performance and durability in low-temperature hydrogen fuel cells, Energy, 226 (2021) 120318. Figure 1