Ultrathin ternary PtNiRu nanowires for enhanced oxygen reduction and methanol oxidation catalysis via d-band center regulation.

Direct methanol fuel cells rely on the efficiency of their anode/cathode electrocatalysts to facilitate the methanol oxidation reaction and oxygen reduction reaction, respectively. Platinum-based nanocatalysts are at the forefront due to their superior catalytic properties. However, the high-cost, scarcity, and low CO tolerance of platinum pose challenges for the scalable application of DMFCs. Herein, we report novel ultrathin ternary PtNiRu alloy nanowires to improve Pt utilization and CO tolerance. These novel electrocatalysts incorporate the oxophilic metal Ru into ultrathin PtNi nanowires, aiming to enhance the intrinsic activity of platinum while leveraging the long-term durability and high utilization efficiency provided by the bimetallic synergistic effect. The PtNiRu NWs significantly enhance both mass activity and specific activity for ORR, performing about 6.9 times and 3.9 times better than commercial Pt/C, respectively. After a rigorous durability test of 10,000 cycles, the PtNiRu NWs only exhibited a 25.2 % loss in mass activity. Additionally, for MOR, the MA and SA of PtNiRu NWs exceed that of Pt/C catalyst by 4.30 and 2.72 times, respectively, and exhibit exceptional resistance to CO poisoning. Theoretical insights from density functional theory calculations suggest that the introduction of Ru modulates the d-band center of the surface Pt atoms, which contributes to decreased binding strength of oxygenated species and an elevated dissolution potential, substantiating the enhanced performance metrics, and the durability enhancement stems from the stronger PtM bonds than those in PtNiRu NWs resulted from PtRu covalent interactions. These findings not only provide a new perspective on platinum-based nanocatalysts but also significantly advance the quest for more efficient and durable electrocatalysts for DMFCs, representing a substantial stride in fuel cell technology.

Electronic and Geometric Effects Endow PtRh Jagged Nanowires with Superior Ethanol Oxidation Catalysis.

Complete ethanol oxidation reaction (EOR) in C1 pathway with 12 transferred electrons is highly desirable yet challenging in direct ethanol fuel cells. Herein, PtRh jagged nanowires synthesized via a simple wet-chemical approach exhibit exceptional EOR mass activity of 1.63 A mgPt-1 and specific activity of 4.07 mA cm-2 , 3.62-fold and 4.28-folds increments relative to Pt/C, respectively. High proportions of 69.33% and 73.42% of initial activity are also retained after chronoamperometric test (80 000 s) and 1500 consecutive potential cycles, respectively. More importantly, it is found that PtRh jagged nanowires possess superb anti-CO poisoning capability. Combining X-ray absorption spectroscopy, X-ray photoelectron spectroscopy as well as density functional theory calculations unveil that the remarkable catalytic activity and CO tolerance stem from both the Rh-induced electronic effect and geometric effect (manifested by shortened Pt─Pt bond length and shrinkage of lattice constants), which facilitates EOR catalysis in C1 pathway and improves reaction kinetics by reducing energy barriers of rate-determining steps (such as *CO → *COOH). The C1 pathway efficiency of PtRh jagged nanowires is further verified by the high intensity of CO2 relative to CH3 COOH/CH3 CHO in infrared reflection absorption spectroscopy.

Integration of multiple advantages into one catalyst: non-CO pathway of methanol oxidation electrocatalysis on surface Ir-modulated PtFeIr jagged nanowires.

Developing highly active methanol oxidation electrocatalysts with superior anti-CO poisoning capability remains a grand challenge. Herein, a simple strategy was employed to prepare distinctive PtFeIr jagged nanowires with Ir located at the shell and Pt/Fe located at the core. The Pt64Fe20Ir16 jagged nanowire possesses an optimal mass activity of 2.13 A mgPt-1 and specific activity of 4.25 mA cm-2, giving the catalyst a great edge over PtFe jagged nanowire (1.63 A mgPt-1 and 3.75 mA cm-2) and Pt/C (0.38 A mgPt-1 and 0.76 mA cm-2). The in-situ Fourier transform infrared (FTIR) spectroscopy and differential electrochemical mass spectrometry (DEMS) unravel the origin of extraordinary CO tolerance in terms of key reaction intermediates in the non-CO pathway. Density functional theory (DFT) calculations add to the body of evidence that the surface Ir incorporation transforms the selectivity from CO pathway to non-CO pathway. Meanwhile, the presence of Ir serves to optimize surface electronic structure with weakened CO binding strength. We believe this work will advance the understanding of methanol oxidation catalytic mechanism and provide some insight into structural design of efficient electrocatalysts.

PtIrM (M = Ni, Co) jagged nanowires for efficient methanol oxidation electrocatalysis.

It remains a huge challenge to develop methanol oxidation electrocatalysts with remarkable catalytic activity and anti-CO poisoning capability. Herein, PtIrNi and PtIrCo jagged nanowires are successfully synthesized via a facile wet-chemical approach. Pt and Ir components are concentrated in the exterior and Ni is concentrated in the interior of PtIrNi jagged nanowires, while PtIrCo jagged nanowires feature the homogeneous distribution of constituent metals. The PtIrNi and PtIrCo jagged nanowires exhibit mass activities of 1.88 A/mgPt and 1.85 A/mgPt, respectively, 3.24 and 3.19 times higher than that of commercial Pt/C (0.58 A/mgPt). In-situ Fourier transform infrared spectroscopy indicates that CO2 was formed at a very low potential for both nanowires, in line with the high ratio of forward current density to backward current density for PtIrNi jagged nanowires (1.30) and PtIrCo jagged nanowires (1.46) relative to Pt/C (0.76). Also, the CO stripping and X-ray photoelectron spectroscopy results substantiate the remarkable CO tolerance of the jagged nanowires. Besides, the two jagged nanowires possess exceptional activities toward ethanol and ethylene glycol oxidation reactions. This work provides a novel line of thought in terms of rational design of alcohol oxidation electrocatalysts with distinctive nanostructures.