Adsorption of CO at Palladium Monolayers Deposited on Pt(111) Electrodes. Combined Spectroelectrochemical and Theoretical Study

2D noble metals: growth peculiarities and prospects for hydrogen evolution reaction catalysis

High-performance electrocatalysts for the hydrogen evolution reaction are of interest in the development of next-generation sustainable hydrogen production systems. Although expensive platinum-group metals have been recognized as the most effective HER catalysts, there is an ongoing requirement for the discovery of cost-effective electrode materials. This paper reveals the prospects of two-dimensional (2D) noble metals, possessing a large surface area and a high density of active sites available for hydrogen proton adsorption, as promising catalytic materials for water splitting. An overview of the synthesis techniques is given. The advantages of wet chemistry approaches for the growth of 2D metals over deposition techniques show the potential for kinetic control that is required as a precondition to prevent isotropic growth. An uncontrolled presence of surfactant-related chemicals on a 2D metal surface is however the main disadvantage of kinetically controlled growth methods, which stimulates the development of surfactant-free synthesis approaches, especially template-assisted 2D metal growth on non-metallic substrates. Recent advances in the growth of 2D metals using a graphenized SiC platform are discussed. The existing works in the field of practical application of 2D noble metals for hydrogen evolution reaction are analyzed. This paper shows the technological viability of the "2D noble metals" concept for designing electrochemical electrodes and their implementation into future hydrogen production systems, thereby providing an inspirational background for further experimental and theoretical studies.

Substrate mediated properties of gold monolayers on SiC

In light of their unique physicochemical properties two-dimensional metals are of interest in the development of next-generation sustainable sensing and catalytic applications. Here we showcase results of the investigation of the substrate effect on the formation and the catalytic activity of representative 2D gold layers supported by non-graphenized and graphenized SiC substrates. By performing comprehensive density functional theory (DFT) calculations, we revealed the epitaxial alignment of gold monolayer with the underlying SiC substrate, regardless of the presence of zero-layer graphene or epitaxial graphene. This is explained by a strong binding energy (∼4.7 eV) of 2D Au/SiC and a pronounced charge transfer at the interface, which create preconditions for the penetration of the related electric attraction through graphene layers. We then link the changes in catalytic activity of substrate-supported 2D Au layer in hydrogen evolution reaction to the formation of a charge accumulation region above graphenized layers. Gold intercalation beneath zero-layer graphene followed by its transformation to quasi-free-standing epitaxial graphene is found to be an effective approach to tune the interfacial charge transfer and catalytic activity of 2D Au. The sensing potential of substrate-supported 2D Au was also tested through exploring the adsorption behaviour of NH₃, NO₂ and NO gas molecules. The present results can be helpful for the experimental design of substrate-supported 2D Au layers with targeted catalytic activity and sensing performance.

Electrocatalysis of fuel cells reaction on Pt and Pt-bimetallic anode catalysts: A selective review

In this review we selectively summarize recent progress, primarily from our laboratory, in the development of interrelationships between the kinetics of the fuel cells reactions and the structure/composition of anode catalysts. The focus is placed on two types of metallic surfaces: platinum single crystals and bimetallic surfaces based on Pt. In the first part it was illustrated that the hydcogen reaction is structure sensitive process, with Pt(110) being an order of magnitude more active than either of the atomically "flatter" (100) and (111) surfaces. The hydrogen reaction on Pt(hkl) modified by pseudomorphic Pd (sub)monolayers shows the "volcano-like" behavior, having the maximum rate on Pt(111) modified by 1 ML of Pd. The Pt(111)-Pd system is used to demonstrate how the energetics of intermediates formed in the hydrogen reaction is affected by interfacial bonding and energetic constraints produced between pseudomorphic Pd films and the Pt(111) substrate. In the second part it was shown that the oxidation of Ha in the presence of CO occurs concurrently with CO oxidation on Pt and Pt bimetallic surfaces. The Pt-Ru system is used to demonstrate that both the bifunctional effect and the ligand effect contribute to the influence of Ru on the CO oxidation rate and for Hz oxidation process in the presence of CO. The knowledge is then used to create the real-life catalyst with the catalytic activities which are, to the greatest extend possible similar to the tailor-made surface.