Ethanol Oxidation on Sn-modified Pt Single-Crystal Electrodes: New Mechanistic Insights from On-line Electrochemical Mass Spectrometry

The need for robust model systems in the study of hybrid interfaces for photocatalysis and photoelectrocatalysis

Small molecule conversion to value-added products using renewable energy sources has emerged as a promising strategy to mitigate our reliance on fossil fuels. Hybrid materials that integrate the strengths of photoabsorbers and co-catalysts (electrocatalysts) are essential for maximizing the efficiency of photochemical (PC) and photoelectrochemical (PEC) systems. In this perspective, we will focus on the need for fundamental studies with a strong emphasis on the importance of beginning with well-defined hybrid interfaces. A particular focus is given to small molecule adsorption studies that correlate surface structure and chemistry to reactivity, highlighting its potential in characterizing complex interfaces. We also make the case for understanding how light and electrochemical environments influence surface structure, adsorption, and reactivity and should be considered in model hybrid system design. Finally, we provide a framework to connect the theory and experiment of model hybrid surfaces to provide a molecular understanding of PC and PEC at these interfaces and accelerate our integration of these materials into real systems capable of meeting our renewable energy needs.

Shape-Controlled Nanoparticles as Anodic Catalysts in Low-Temperature Fuel Cells

The great dependence of the electrocatalytic activity of most electrochemical reactions on the catalytic surface area and specific surface structure is widely accepted. Building on the extensive knowledge already available on single-crystal surfaces, this Perspective discusses the recent progress made in low-temperature fuel cells through the use of the most active shape-controlled noble metal-based nanoparticles. In particular, we will focus on discussing structure-composition-reactivity correlations in methanol, ethanol, and formic acid oxidation reactions and will offer a general vision of future needs.

Pt-Richcore/Sn-Richsubsurface/Ptskin Nanocubes As Highly Active and Stable Electrocatalysts for the Ethanol Oxidation Reaction

Direct ethanol fuel cells are one of the most promising electrochemical energy conversion devices for portable, mobile and stationary power applications. However, more efficient and stable and less expensive electrocatalysts are still required. Interestingly, the electrochemical performance of the electrocatalysts toward the ethanol oxidation reaction can be remarkably enhanced by exploiting the benefits of structural and compositional sensitivity and control. Here, we describe the synthesis, characterization, and electrochemical behavior of cubic Pt-Sn nanoparticles. The electrochemical activity of the cubic Pt-Sn nanoparticles was found to be about three times higher than that obtained with unshaped Pt-Sn nanoparticles and six times higher than that of Pt nanocubes. In addition, stability tests indicated the electrocatalyst preserves its morphology and remains well-dispersed on the carbon support after 5000 potential cycles, while a cubic (pure) Pt catalyst exhibited severe agglomeration of the nanoparticles after a similar stability testing protocol. A detailed analysis of the elemental distribution in the nanoparticles by STEM-EELS indicated that Sn dissolves from the outer part of the shell after potential cycling, forming a ∼0.5 nm Pt skin. This particular atomic composition profile having a Pt-rich core, a Sn-rich subsurface layer, and a Pt-skin surface structure is responsible for the high activity and stability.