Understanding of Correlation between Electronic Properties and Sulfur Tolerance of Pt-Based Catalysts for Hydrogen Oxidation

Abstract

Renewable power-derived green hydrogen distributed via natural gas networks is considered one of the viable routes to drive the decarbonization of transportation and distributed power generation, while a trace amount of sulfur impurities is one of the key factors that affect the durability and life cycle expense of proton-exchange membrane fuel cells (PEMFCs) for end users. Herein, we explore the underlying effect of sulfur resistance for Ptbased hydrogen oxidation reaction (HOR) electrocatalysts devoted to high-performance and durable PEMFCs. Two typical electrocatalysts, Pt/C with pure Pt nanoparticles (NPs) and PtCo/C with Pt 3 Co-alloy-core-Pt-skin NPs, were investigated to demonstrate the structure−property relation for Pt-based electrocatalysts. It was revealed that the PtCo/C demonstrated alleviated sulfur poisoning with the adsorption rate constant reduced by 21.7% compared with Pt/C, and the desorption of the adsorbed sulfur was also more favorable with Pt−S bond decomposition temperature lowered by approximately 25 °C. Characterization indicated that sulfur was predominantly adsorbed in the edge mode for PtCo/C, but in a comparable edge and bridge mode for Pt/C, which caused the strengthened Pt−S binding by the chelation effect for Pt/C. The lowered d-band center of surface Pt for PtCo/C, tuned by electron transfer from Co to Pt and Pt lattice strain, was also found responsible for the weakened Pt−S interaction. The recovery test based on electro-oxidation suggested that PtCo/C also outperformed Pt/C with faster and more thorough release of HOR active sites. The SO 42− species derived from electro-oxidation of S 2− was more apt to adsorb on Pt/C than PtCo/C because of its stronger affinity to SO 4 2− caused by the higher d-band center of Pt. Therefore, it is clarified that adequate modification of the Pt d-band center, for example, negatively tuned for the state-of-the-art Pt/C, is crucial to improve the sulfur resistance and recovery capability for Pt-based electrocatalysts while reserving comparable HOR activity. In particular, the investigated PtCo/C electrocatalyst is a better choice over Pt/C for more durable PEMFC anodes.

Challenges of Green Production of 2,5‐Furandicarboxylic Acid from Bio‐Derived 5‐Hydroxymethylfurfural: Overcoming Deactivation by Concomitant Amino Acids

“…A change in sulfur adsorption was reported for different alloys in literature; [26] for example, Lakhapatri and Abraham [26b] could show an increase of sulfur tolerance for a Ni‐based catalyst by Rh promotion. Furthermore, Ke et al [26a] . showed an improved sulfur tolerance of a PtCo bimetallic catalyst compared to a monometallic Pt catalyst.…”

Intriguing H2S Tolerance of the PtRu Alloy for Hydrogen Oxidation Catalysis in PEMFCs: Weakened Pt–S Binding with Slower Adsorption Kinetics

“…Both catalysts demonstrate a gradual decrease in ECSAs with the increase in testing time, but the degradation rate is much different (Figure a,b). Through fitting the curves of ECSA loss with time, the adsorption rate of S 2– on Pt sites was quantified according to our previous investigation results θ normalS = A ( 1 − e − k f s C S t ) where θ s presents the sulfur coverage on the Pt surface, C S is the concentration of S 2– , k fs is the adsorption rate constant, and t is time.…”

“…Although the adsorption energies of these sites adsorbed on or near Ru atoms are higher on the PtRu alloy surface compared with pure Pt, the lowered d-band center of Pt atoms induced by Ru leads to a weakened interaction between Pt and S and thus improves antipoisoning capability of PtRu/C. In our previous work, we explored the underlying effect of sulfur resistance for Pt-based HOR electrocatalysts and found that the sulfur tolerance of Pt-based catalysts is dependent on the electronic structure of Pt . Therefore, the PtRu alloy catalyst significantly reduces the absorbability on Pt active sites toward sulfur species through modification of the Pt electronic structure, making it a promising anode material for long-term application of PEMFCs.…”

“…Through fitting the curves of ECSA loss with time, the adsorption rate of S 2− on Pt sites was quantified according to our previous investigation results. 41 = A( 1 e ) k C t S fs S (7) where θ s presents the sulfur coverage on the Pt surface, C S is the concentration of S 2− , k fs is the adsorption rate constant, and t is time. According to this equation, the poisoning rate constant (k fs C S ) was found to be increased with the increase in temperature through the exponential fitting of experimental data tested at different temperatures (Figure 7c).…”

Platinum–Ruthenium Single Atom Alloy as a Bifunctional Electrocatalyst toward Methanol and Hydrogen Oxidation Reactions

“…Fuel cells, such as direct methanol fuel cells (DMFCs) − and hydrogen oxygen fuel cells (HOFCs), − are one of the most promising candidates to replace fossil fuels due to their nonpolluting and efficient energy conversion efficiency. − The methanol oxidation reaction (MOR) and hydrogen oxidation reaction (HOR) belong to the anode reactions of DMFCs and HOFCs, respectively, and have been extensively studied. − To date, Pt has been used as key materials for both MOR and HOR because of their superior activity compared to other metal materials. − Thus, developing Pt-based electrocatalysts with high performance attracts extensive research and has great significance. − …”