Liangliang Zou

Conversion of PtNi alloy from disordered to ordered for enhanced activity and durability in methanol-tolerant oxygen reduction reactions

The development of cost-effective oxygen reduction reaction (ORR) catalysts with a high methanol tolerance and enhanced durability is highly desirable for direct methanol fuel cells. This work focuses on the conversion of PtNi nanoparticles from a disordered solid solution to an ordered intermetallic compound. Here the effect of this conversion on ORR activity, durability, and methanol tolerance are characterized. X-ray diffraction and transmission electron microscopy results confirm the formation of ordered PtNi intermetallic nanoparticles with high dispersion and a mean particle size of about 7.6 nm. The PtNi intermetallic nanoparticles exhibited enhanced mass and specific activities toward the methanol-tolerant ORR in pure and methanol-containing electrolytes. The specific activity of the ORR at 0.85 V on the PtNi intermetallic nanoparticles is almost 6 times greater than on commercial Pt/C and 3 times greater than on disordered PtNi alloy. Durability tests indicated a minimal loss of ORR activity for PtNi intermetallic nanoparticles after 5,000 potential cycles, whereas the ORR activity decreased by 28% for disordered PtNi alloy. The enhanced methanoltolerant ORR activity and durability may be attributed to the structural and compositional stabilities of the ordered PtNi intermetallic nanoparticles compared relative to the stabilities of the disordered PtNi alloy, strongly suggesting that the PtNi intermetallic nanoparticles may serve as highly active and durable methanol-tolerant ORR electrocatalysts for practical applications.

Plasmonic Pd Nanoparticle- and Plasmonic Pd Nanorod-Decorated BiVO4 Electrodes with Enhanced Photoelectrochemical Water Splitting Efficiency Across Visible-NIR Region.

The photoelectrochemical (PEC) water splitting performance of BiVO4 is partially hindered by insufficient photoresponse in the spectral region with energy below the band gap. Here, we demonstrate that the PEC water splitting efficiency of BiVO4 electrodes can be effectively enhanced by decorating Pd nanoparticles (NPs) and nanorods (NRs). The results indicate that the Pd NPs and NRs with different surface plasmon resonance (SPR) features delivered an enhanced PEC water splitting performance in the visible and near-infrared (NIR) regions, respectively. Considering that there is barely no absorption overlap between Pd nanostructures and BiVO4 and the finite-difference time domain (FDTD) simulation indicating there are substantial energetic hot electrons in the vicinity of Pd nanostructures, the enhanced PEC performance of Pd NP-decorated BiVO4 and Pd NR-decorated BiVO4 could both benefit from the hot electron injection mechanism instead of the plasmon resonance energy transfer process. Moreover, a combination of Pd NPs and NRs decorated on the BiVO4 electrodes leads to a broad-band enhancement across visible-NIR region.

High performance MWCNT–Pt nanocomposite-based cathode for passive direct methanol fuel cells

Reduction of the Pt loading required in cathodes is crucial for the development of passive direct methanol fuel cells (DMFCs). Herein, a novel membrane electrode assembly (MEA) that utilizes a MWCNT–Pt nanocomposite cathodic catalyst layer (CCL) with a 3D network structure is shown to require significantly less Pt loading. With a CCL Pt loading of 0.5 mg cm−2, the maximum power density of the prepared DMFC is 19.2 ± 0.4 mW cm−2 using 2.0 M methanol solution at 25 ± 1 °C, which is higher than that of the power density by a conventional MEA with twice the Pt loading (1.0 mg cm−2). Electrochemical tests show that the structure of the CCL decreases the charge transfer resistance of the cathode reaction and greatly increases the cathode catalyst utilization in comparison with the conventional MEA. The enhanced MEA performance is attributed to the discontinuous distributions of the Pt MWCNT structures and the formation of a cross-twined network within the CCL. This study could provide a promising way to reduce the cost of future commercialized DMFCs.