Tweaking Nickel with Minimal Silver in a Heterogeneous Alloy of Decahedral Geometry to Deliver Platinum‐like Hydrogen Evolution Activity

Abstract

Five-fold intertwined Ag x Ni 1Àx (x = 0.01-0.25) heterogeneous alloynanocrystal (NC) catalysts,prepared through unique reagent combinations,a re presented. With only ca. 5at% Ag (AgNi-5), Pt-like activity has been achieved at pH 14. To reachacurrent density of 10 mA cm À2 the extremely stable AgNi-5 requires an overpotential of 24.0 AE 1.2 mV as compared to 20.1 AE 0.8 mV for 20 %P t/C,b oth with equal catalyst loading of 1.32 mg cm À2 .T he turnover frequency (TOF) is as high as 2.1 H 2 s À1 at 50 mV (vs.R HE). Sitespecific elemental analyses show the Ag:Ni compositional variation, where the apex and edges of the decahedra are Agrich, therebye xposing Ni onto the faces to achieve maximum charge transport for an exceptional pH universal HER activity. DFT calculations elucidate the relative H-atom adsorption capability of the Ni centers as af unction of their proximity to Ag atom.

Intra-Lattice Inverse Charge Transfer in Bimetallic Electrocatalysts

“…9 Intermetallic charge transfer often leads to an asymmetric electronic distribution at the catalytically active metal centers, impacting the adsorption and desorption of reaction intermediates. [11][12][13] In addition, the catalyst-support charge transfer interactions also influence the overall reactivity. 14,15 Charge transfer follows this directive unless it is overpowered by an opposing voltage bias, for example, during reduction, electron transfer occurs from more EN substrates such as Ni foam and carbon to less EN metal components of the catalyst.…”

“…14,15 Charge transfer follows this directive unless it is overpowered by an opposing voltage bias, for example, during reduction, electron transfer occurs from more EN substrates such as Ni foam and carbon to less EN metal components of the catalyst. 13,16 In the absence of an external driving force, reversing the path of charge transfer is apparently incongruous.…”

Experimental and theoretical study on hydrogen production by using Ag nanoparticle‐decorated graphite/Ni cathode

“…Ag‐Ni alloys have also shown high efficiency for HER despite the complete immiscibility of the metals, large lattice mismatch by 14% (Ni: 0.352 nm and Ag: 0.408 nm), and lower surface energy of Ag as suggested by theoretical calculations. However, the difference in electrochemical potentials causes difficulty in the synthesis of the bimetallic alloy due to Ag and Ni to phase‐segregate ending up with different elemental phases at all temperatures 46 . Therefore, in the current study, Ag‐decorated metallic Ni/graphite electrode denoted as G/Ni/Ag is selected as a suitable arrangement rather than its bimetallic alloy.…”

“…However, the difference in electrochemical potentials causes difficulty in the synthesis of the bimetallic alloy due to Ag and Ni to phase-segregate ending up with different elemental phases at all temperatures. 46 Therefore, in the current study, Ag-decorated metallic Ni/graphite electrode denoted as G/Ni/Ag is selected as a suitable arrangement rather than its bimetallic alloy.…”

A Single‐Atom Manipulation Approach for Synthesis of Atomically Mixed Nanoalloys as Efficient Catalysts

“…To overcome the heterogeneous structure, the synthetic process usually involves the use of harsh conditions. [7][8][9][10][11] For high-temperature solid-state methods, a large amount of energy is required to break down the heterogeneous phase to form a stable new homogeneous structure. Consequently, this process takes place at very high temperatures, which unfortunately can easily destroy the structure of catalysts, leading to activity loss.…”