Improved bi-functional oxygen electrocatalytic performance of Pt–Ir alloy nanoparticles embedded on MWCNT with Pt-enriched surfaces

Abstract

Multi-walled carbon nanotube supported PteIr nanoparticles (PteIr/MWCNT) with different elemental ratios were synthesized by one-pot co-reduction approach under ambient conditions. The PteIr catalysts exhibit improved bi-functional activity towards oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) and its electrocatalytic performance was clearly established using different physiochemical characterization techniques. The PteIr composition of 2:1 has a higher electrochemical surface area (ECSA) of about 85.3 m 2 /g compared to other compositions (3:1 and 1:1) and Pt/MWCNT due to the effect of particle size distribution. The improved ORR/OER activity was found to be 139.4 and 740 mA/mg, respectively, for PteIr(2:1)/MWCNT with the potential difference of 760 mV for oxygen bi-functional activity. Furthermore, PteIr(2:1)/MWCNT showed much better stability for ORR compared to other compositions and Pt/MWNCT catalysts, i.e., around 76% of its initial ECSA retained with <20 mV shift in half-wave potential was obtained even after 10,000 potential cycles in acidic medium. It is believed that the Pt enriched surface, amount of Ir content, induced electronic and geometric effects play a vital role on the electrocatalytic activity enhancement of PteIr(2:1)/MWNCT as effective bi-functional oxygen electrode.

Enhanced electrochemical hydrogen oxidation reaction and suppressed hydrogen peroxide generation properties on Pt/Ir(111) bimetallic surfaces

“…Because the bonding of H ad to the Pt and Ir surfaces is considered to be stronger compared with that for optimal HOR activity enhancement, 31,32 appropriately weakened H ad bonding would show maximum HOR activity for Pt x ML /Ir(111). According to the literature, the coexistence of Pt and Ir can result in interatomic charge transfer 13,33 and this is consistent with the chemical shift of Pt4f observed in the present study (Fig. S.2, ESI.…”

“…Also, the value of i T /| i S | for Pt 0.3ML /Ir(111) (blue) remained almost at the noise level below 0.2 V, though i T /| i S | slightly increased in E S > 0.2 V. In contrast, the value of i T /| i S | for Pt 0.5ML /Ir(111) (red) exhibited marked H 2 O 2 generation throughout the potential range of 0.06–0.3 V. The results indicate that the value of x (Pt-deposited thicknesses) less than 0.5 ML for Pt x ML /Ir(111) tends to suppress the H 2 O 2 generation in the potential region of <0.2 V, which seems consistent with several studies reported for H 2 O 2 generation through ORR on the Pt–Ir catalysts with Pt-enriched surfaces. 33,38,39 The present study revealed that the Ir-enriched surfaces of Ir–Pt bimetallic materials, contrary to the Pt-enriched surfaces, are effective in mitigating the H 2 O 2 generation.…”

“…Because the bonding of H ad to the Pt and Ir surfaces is considered to be stronger compared with that for optimal HOR activity enhancement, 31,32 appropriately weakened H ad bonding would show maximum HOR activity for Pt xML /Ir(111). According to the literature, the coexistence of Pt and Ir can result in interatomic charge transfer 13,33 34 Since the upshift of the dband center tends to strengthen the hydrogen binding, 35,36 the hydrogen binding strength of surface Pt and Ir domains can be expected to become lower and higher, respectively. From this perspective, deposited Pt sites rather than substrate Ir sites are more likely to contribute to the HOR activity enhancement for Pt xML /Ir(111).…”

Exploring high-efficiency electrocatalysts of metal-doped two-dimensional C4N for oxygen reduction, oxygen evolution, and hydrogen evolution reactions by first-principles screening

“…[1][2][3] The hydrogen evolution reaction (HER), oxygen reduction reaction (ORR), and oxygen evolution reaction (OER) are the core reactions of the systems mentioned above, and high-efficiency catalysts are required to accelerate the rate of these reactions. [4][5][6][7][8][9][10] Precious metal [11][12][13] and metal oxide materials 14,15 have long been used as efficient electrocatalysts for the HER/ORR/OER. However, their high cost and scarcity limit the large-scale application of renewable energy technologies.…”

Nanophase-Engineered Bifunctional Catalysts for Oxygen Electrodes in High-Performance Unitized Regenerative Fuel Cells

“…Unfortunately, the as-synthesized Pt–Ir alloys display a poor bifunctional activity toward ORR and OER relative to pure Pt and Ir. Xu et al further studied the composition-dependent bifunctional activity of Pt–Ir alloys on carbon nanotubes fabricated by one-pot co-reduction and found that the high proportion of stable IrO x species on Ir surface would decay ORR activity, while the presence of the Pt component can seriously weaken the OER, thereby resulting in a poor bifunctional performance . Another strategy to address the above issue may be nanophase engineering of active Pt and Ir parts to form a reasonable phase structure with double active sites for ORR and OER, respectively .…”