Iterative redox activation promotes interfacial synergy in an Ag/CuxO catalyst for oxygen reduction

Park, Young-Tae; Shin, Kihyun; Lee, Changsoo; Lee, Sang Yeon; Lee, Yong‐Kul; Kim, Chang-Hee; Cho, Hyun‐Seok; Henkelman, Graeme; Lee, Hyuck Mo

doi:10.1016/j.cej.2022.136966

Cited by 12 publications

(5 citation statements)

References 60 publications

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“…Instead, this phenomenon is associated with an activation process taking place upon potential cycling, which presumably increases the stability and reorganization of Ag surface atoms. 55,56 As expected, pure Ag thin films exhibit the largest Ag ECSA among all samples, which is maintained through electrochemical measurements. However, it was noted that the measured Ag AECSA was largely reduced for the sample with only ORR measurements.…”

Section: ■ Results and Discussionsupporting

confidence: 79%

“…Although the overall surface Ag enrichment in ORR bimetallic samples is justified by the differences in surface energies, the further increase in Ag ECSA in all samples when CVs are recorded prior to the ORR measurements cannot be explained in terms of surface energies or oxophilicity. Instead, this phenomenon is associated with an activation process taking place upon potential cycling, which presumably increases the stability and reorganization of Ag surface atoms. , As expected, pure Ag thin films exhibit the largest Ag ECSA among all samples, which is maintained through electrochemical measurements. However, it was noted that the measured Ag AECSA was largely reduced for the sample with only ORR measurements.…”

Section: Resultssupporting

confidence: 62%

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Tuning the Activity of Silver Alloys for the Oxygen Reduction Reaction in Alkaline Media

Montserrat‐Sisó

Wickman

2023

ACS Appl. Energy Mater.

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Ag-based catalysts have recently attracted much attention as potential candidates to substitute costly Pt-based electrocatalysts for the oxygen reduction reaction (ORR) in alkaline media. Although the electrocatalytic activity of Pt-based alloys is known to exhibit a strong dependence on their electronic structures, a relationship between electronic structure and the ORR mechanism in Ag-based alloys still remains to be elucidated. Herein, by means of physical vapor deposition, we prepare Ag binary thin films (CoAg, CuAg, AuAg, and FeAg) with well-controlled compositions as a tool to investigate the ORR mechanism on Ag surfaces. The bimetallic thin films are evaluated for their ORR performance in alkaline media, and their specific activity at 0.8 VRHE is shown to correlate with the Ag electronic structure. Even though all thin films show different responses to potential cycling, all bimetallic samples exhibit a surface Ag enrichment after ORR. It is shown that the ORR occurs through different mechanisms on these Ag-rich surfaces, which in turn is potential-dependent. Tafel slopes reveal faster ORR kinetics at low overpotentials on all surfaces, whereas only CuAg surpasses pure Ag at higher overpotentials. Moreover, despite their incomplete O2 reduction, CuAg and AuAg exhibit an overall superior ORR activity over pure Ag, with a more than 2-fold increase in specific activity at 0.8 VRHE attributed to enhancements originating from electronic effects and surface defects, respectively. Since the potential-dependent improved ORR mechanism observed for Ag bimetallic samples makes a rational design of Ag-based electrocatalysts difficult, these results aim to provide insights for a more tailored design of electrocatalysts by shedding light on the mechanisms through which the ORR kinetics are improved on Ag surfaces in alkaline media.

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Section: ■ Results and Discussionsupporting

confidence: 79%

Section: Resultssupporting

confidence: 62%

Tuning the Activity of Silver Alloys for the Oxygen Reduction Reaction in Alkaline Media

Montserrat‐Sisó

Wickman

2023

ACS Appl. Energy Mater.

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“…Encouraged by the high MEA performance of the NiCuCr/C anode, we fabricated a totally PGM-free MEA by using the NiCuCr/C as the anode and commercial Ag/C as the cathode. Ag showed high ORR performance in alkaline conditions but much lower cost than PGMs 54 – 57 . High-performance HEMFCs using Ag as the cathode have been reported 21 , 58 , 59 .…”

Section: Resultsmentioning

confidence: 99%

Tuning the apparent hydrogen binding energy to achieve high-performance Ni-based hydrogen oxidation reaction catalyst

Wang,

Liu,

Fang

et al. 2024

Nat Commun

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High-performance platinum-group-metal-free alkaline hydrogen oxidation reaction catalysts are essential for the hydroxide exchange membrane fuel cells, which generally require high Pt loadings on the anode. Herein, we report a highly active hydrogen oxidation reaction catalyst, NiCuCr, indicated by the hydroxide exchange membrane fuel cell with a high peak power density of 577 mW cm−2 (18 times as high as the Ni/C anode) and a stability of more than 150 h (a degradation rate slower by 7 times than the Ni/C anode). The spectroscopies demonstrate that the alloy effect from Cu weakens the hydrogen binding, and the surface Cr2O3 species enhance the interfacial water binding. Both effects bring an optimized apparent hydrogen binding energy and thus lead to the high hydrogen oxidation reaction performance of NiCuCr. These results suggest that the apparent hydrogen binding energy determines the hydrogen oxidation reaction performance and that its tuning is beneficial toward high electrocatalytic performance.

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“…Chemical reaction between Ag + and Co 2+ cations in the alkaline solution was confirmed as shown in Supporting Information. Due to the redox potential of Ag + (eq ) and Co 2+ (eq ), a redox reaction in a basic condition gave their precipitates, metallic Ag and Co 3 O 4 , respectively (eq ), which were confirmed by X-ray diffraction (XRD) (Figure S1). In the present study, the resulting precipitation mixture is termed as an Ag–Co 3 O 4 composite. Ag + + e − → Ag , E 0 = 1.06 V Co 2 + → Co 3 + + e − , E 0 = − 1.8 V 2Ag + + 3Co 2 + + 8OH − → 2Ag false↓ + Co 3 O 4 false↓ + 4H 2 normalO …”

Section: Results and Discussionmentioning

confidence: 99%

Simultaneous Photodeposition of an Ag–Co Cocatalyst in Different pH Conditions To Improve the Activity of Calcium Titanate Photocatalyst for Carbon Dioxide Reduction with Water

Qiu,

Yamamoto,

Fudo

et al. 2023

ACS Appl. Energy Mater.

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Iterative redox activation promotes interfacial synergy in an Ag/CuxO catalyst for oxygen reduction

Cited by 12 publications

References 60 publications

Tuning the Activity of Silver Alloys for the Oxygen Reduction Reaction in Alkaline Media

Tuning the Activity of Silver Alloys for the Oxygen Reduction Reaction in Alkaline Media

Tuning the apparent hydrogen binding energy to achieve high-performance Ni-based hydrogen oxidation reaction catalyst

Simultaneous Photodeposition of an Ag–Co Cocatalyst in Different pH Conditions To Improve the Activity of Calcium Titanate Photocatalyst for Carbon Dioxide Reduction with Water

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