Highly Durable and Active Pt/Sb-Doped SnO₂ Oxygen Reduction Reaction Electrocatalysts Produced by Atomic Layer Deposition

Abstract

Platinum supported on mixed-metal oxides (MMOs) are a class of active and durable cathode catalysts for proton exchange membrane fuel cell (PEMFC) due to a combination of the high oxidative stability of the supports and strong metal–support interactions (SMSI) that enable them to exceed the activity of Pt/C. Herein, we solve a significant remaining challenge with Pt/MMO systems, namely, the relatively low surface area and porosity. This is achieved by dispersing nearly uniform Pt clusters by using atomic layer deposition (ALD) on highly conductive (6.2 S/cm) and stable antimony-doped tin dioxide (ATO) support. ALD-Pt/ATO exhibited a significantly higher electrochemically active surface area (ECSA) (74 m2/g) and oxygen reduction reaction (ORR) catalytic activity (102 mA/mgPt at 0.9 V vs RHE) compared to Pt/ATO synthesized by using ethylene glycol (ECSA = 31 m2/gPt, mass activity = 52 mA/mgPt at 0.9 V vs RHE) and formic acid reduction methods (ECSA = 28 m2/gPt, mass activity = 46 mA/mgPt at 0.9 V vs RHE). Further characterization showed that wet chemical methods resulted in poorer Pt particle dispersion, poor control over Pt particle size distribution, and chemical degradation of the support (during Pt deposition). Given the near-ideal Pt particle size distribution of the ALD-Pt/ATO, particle size growth and loss of ECSA was found to be minimal over the course of rigorous potential cycling. Thus, after 10000 potential cycles between 1 and 1.5 V vs RHE, ALD-Pt/ATO and other Pt/ATOs were found to retain 100% of their initial ECSA compared to 57.6% retention for Pt/C. Upon testing in a H2/air PEMFC, following 1000 potential cycles, the change in ALD-Pt/ATO performance was negligible while Pt/C exhibited a 68.2% loss of initial peak power density. Thus, ALD-Pt/ATO is an active and highly durable ORR electrocatalyst in PEMFCs under start-up–shut-down conditions.

Inexpensive gram scale synthesis of porous Ti4O7 for high performance polymer electrolyte fuel cell electrodes

“…The changes in V at j = 1.0 A cm -2 during the cycles, which was previously utilized by Ramani group 5 , were used as a measure of durability as high loads are needed in vehicles. The load cycle durability of the present Pt/Ti 4 O 7 is among the highest of the state-of-the-art Pt/oxide catalysts, 4,5,8,9 There are no conflicts to declare.…”

“…The low cost is another advantage, although additional costs are required to protect the material from oxidation. 3 Several oxide materials, including titanium dioxides, 4,5 titanium suboxides, 6,7 and tin dioxides, 8,9 have been developed as support materials because they are stable in PEFC cathodes, where four times higher platinum loading is currently needed compared with the anodes. 10 However, both the S BET and σ values of the oxides are generally insufficient; the values are often one or even two orders of magnitude lower than those of carbon black, reducing the cell performance.…”

“…Recently, He et al successfully prepared antimony-doped tin dioxide with an exceptionally high σ of 6.2 S cm -1 without disclosing the compression pressure, while the S BET was below 50 m 2 g -1 . 9 The preparation of oxide supports exceeding both thresholds (1) and ( 2) is a major challenge. Magnéli phase titanium suboxides, with a composition that can be expressed as Ti n O 2n-1 , are well known as conductive oxides with a maximum σ at n = 4.…”

Applications of Atomic Layer Deposition in Design of Systems for Energy Conversion

“…[136,41] ALD deposition of the platinum nanoparticles represents one of the optimization routes, and was utilized (in addition to the already mentioned works) also in decoration of carbon nanotubes, [137] of porous TiN supports, [138] or on antimony-doped tin oxide. [139] In these reports the main effort was put into maximalization of the active surface of the platinum catalysts and/or stabilization of the catalytic systems. Besides the need of a maximal active surface area, there are other crucial practical parameters of the platinum-based ORR catalyst emerging from the ways of their use.…”

Metal‐Nitrogen‐Carbon Cluster‐Decorated Titanium Carbide is a Durable and Inexpensive Oxygen Reduction Reaction Electrocatalyst

“…Higher durability in Pt-based ORR catalysts has been obtained by dispersing Pt nanoparticles over corrosion-resistive supports, such as doped TiO 2 , doped SnO 2 , and other metal oxides that can withstand the voltage spikes during start-up/ shut-down cycles. [29][30][31][32][33][34][35][36] In TMN-catalysts, since the TMN-clusters are directly embedded in the matrix, there is a strong effect of the matrix on the stability and ORR activity of the embedded clusters. [37,38] Given the large choice of available TMN clusters coupled with a modest selection of available stable electrocatalyst matrices, [9,39] there is a need for a rational design approach that accounts for active site-matrix interactions to enable efficient identification of TMN cluster/matrix systems having the most promising combination of ORR activity and durability.…”