Experimental study platform for electrocatalysis of atomic-level controlled high-entropy alloy surfaces.

High-entropy alloys (HEAs) have attracted considerable attention to improve performance of various electrocatalyst materials. A comprehensive understanding of the relationship between surface atomic-level structures and catalytic properties is essential to boost the development of novel catalysts. In this study, we propose an experimental study platform that enables the vacuum synthesis of atomic-level-controlled single-crystal high-entropy alloy surfaces and evaluates their catalytic properties.

Surface modification of gold by carbazole dendrimers for improved carbon dioxide electroreduction.

Four types of carbazole dendrimers were applied as modification molecules of Au surfaces to improve carbon dioxide electroreduction. The reduction properties depended on the molecular structures: the highest activity and selectivity to CO was achieved by 9-phenylcarbazole, probably caused by the charge transfer from the molecule to Au.

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

Simultaneous accomplishment of high hydrogen oxidation reaction (HOR) activity and suppressed hydrogen peroxide (HO) generation is desired for anode catalysts of polymer electrolyte fuel cells. 0.3 monolayer-thick-Pt-deposited Ir(111) showed three-fold higher HOR activity than Pt(111) and suppressed HO generation under the detection limit, providing insights for effective catalyst development.

Hydrogen peroxide generation and hydrogen oxidation reactions of vacuum-prepared Ru/Ir(111) bimetallic surfaces.

From the viewpoint of the application of Ir-Ru alloys for the anode of proton exchange membrane fuel cells (PEMFCs), hydrogen peroxide (HO) generation and the hydrogen oxidation reaction (HOR) properties of well-defined Ir-Ru bimetallic surfaces (Ru/Ir(111)) have been investigated using scanning electrochemical microscopy (SECM). Using thermal inter-diffusion of vacuum-deposited Ru and substrate Ir atoms, the topmost surface atomic ratios of Ru/Ir(111) were controlled changing the substrate temperature () during the deposition of 1 monolayer (ML)-thick Ru. Low-energy ion scattering spectroscopy (LE-ISS) estimated the Ru/Ir ratio to be 1 : 1 ( = 673 K), 1 : 2 ( = 773 K), and 1 : 4 ( = 873 K).

Model building analysis - a novel method for statistical evaluation of Pt L-edge EXAFS data to unravel the structure of Pt-alloy nanoparticles for the oxygen reduction reaction on highly oriented pyrolytic graphite.

Extended X-ray absorption fine structure (EXAFS) is a powerful tool to determine the local structure in Pt nanoparticles (NP) on carbon supports, active catalysts for fuel cells. Highly oriented pyrolytic graphite (HOPG) covered with Pt NP gives samples with flat surfaces that allow application of surface science techniques. However, the low concentration of Pt makes it difficult to obtain good quality EXAFS data.

Heterolayered Ni-Fe Hydroxide/Oxide Nanostructures Generated on a Stainless-Steel Substrate for Efficient Alkaline Water Splitting.

Highly active and inexpensive anode materials are required for large-scale hydrogen production using alkaline water electrolysis (AWE). Here, heterolayered nanostructures of Ni-Fe hydroxides/oxides with high activity for the oxygen evolution reaction (OER) were synthesized on a 316 stainless steel (SS) substrate through constant current density electrolysis. The thicknesses, morphologies, and compositions of the nanostructures, generated through dealloying and surface oxidation of the SS elements with severe oxygen microbubble evolution, were dependent on the electrolysis time.

Alloy-composition-dependent oxygen reduction reaction activity and electrochemical stability of Pt-based bimetallic systems: a model electrocatalyst study of Pt/PtNi(111).

The oxygen reduction reaction (ORR) activity and electrochemical stability of well-defined n monolayer (ML)-Pt/PtNi(111) (n = 2 and 4; x = 75, 50, and 25) model electrocatalyst surfaces were investigated in this study. The initial activity of the as-prepared two-monolayered Pt-covered PtNi(111) substrates (2ML-Pt/PtNi(111)) increased with increasing Ni composition in the PtNi(111) substrate. In particular, 2ML-Pt/PtNi(111) showed the initial activity that was 25 times higher than that of clean Pt(111) although the higher Ni composition resulted in destabilization of the catalyst upon the application of potential cycles (PCs).

Ultrahigh Vacuum Synthesis of Strain-Controlled Model Pt(111)-Shell Layers: Surface Strain and Oxygen Reduction Reaction Activity.

In this study, we perform ultrahigh vacuum (UHV) and arc-plasma synthesis of strain-controlled Pt(111) model shells on Pt-Co(111) layers with various atomic ratios of Pt/Co and an oxygen reduction reaction (ORR) activity enhancement trend against the surface strain induced by lattice mismatch between the Pt shell and Pt-Co alloy-core interface structures was observed. The results showed that the Pt(111)-shell with 2.0% compressive surface strain vs intrinsic Pt(111) lattice gave rise to a maximum activity enhancement, ca.

Dealloying of Nitrogen-Introduced Pt-Co Alloy Nanoparticles: Preferential Core-Shell Formation with Enhanced Activity for Oxygen Reduction Reaction.

Voltammetric dealloying is a typical method to synthesize Pt-shell/less-noble metal (M) alloy core nanoparticles (NPs) toward the oxygen reduction reaction (ORR). The pristine nanostructures of the Pt-M alloy NPs should determine the ORR activity of the dealloyed NPs. In this study, we investigated the voltammetric dealloying behavior of the Pt-Co and nitrogen-introduced Pt-Co alloy NPs generated by synchronous arc-plasma deposition of Pt and Co.

Oxygen reduction reaction activity and structural stability of Pt-Au nanoparticles prepared by arc-plasma deposition.

The oxygen reduction reaction (ORR) activity and durability of various Au(x)/Pt100 nanoparticles (where x is the atomic ratio of Au against Pt) are evaluated herein. The samples were fabricated on a highly-oriented pyrolytic graphite substrate at 773 K through sequential arc-plasma depositions of Pt and Au. The electrochemical hydrogen adsorption charges (electrochemical surface area), particularly the characteristic currents caused by the corner and edge sites of the Pt nanoparticles, decrease with increasing Au atomic ratio (x).

Effective shell layer thickness of platinum for oxygen reduction reaction alloy catalysts.

Effects of surface Pt monolayer thickness on electrochemical oxygen reduction reaction of molecular-beam-epitaxially-prepared Pt/Ni/Pt(111) were investigated. The effective thickness of Pt for stabilizing the topmost surface can be deduced to be three monolayers.