A Multisite Strategy for Enhancing the Hydrogen Evolution Reaction on a Nano‐Pd Surface in Alkaline Media

Abstract

The hydrogen evolution reaction (HER) on a noble metal surface in alkaline media is more sluggish than that in acidic media due to the limited proton supply. To promote the reaction, it is necessary to transform the alkaline HER mechanism via a multisite catalyst, which has additional water dissociation sites to improve the proton supply to an optimal level. Here, this study reports a top‐down strategy to create a multisite HER catalyst on a nano‐Pd surface and how to further fine‐tune the areal ratio of the water dissociation component to the noble metal surface in core/shell‐structured nanoparticles (NPs). Starting with Pd/Fe3O4 core/shell NPs, electrochemical cycling is used to tune the coverage of iron (oxy)hydroxide on a Pd surface. The alkaline HER activity of the core/sell Pd/FeOx(OH)2−2x NPs exhibits a volcano‐shaped correlation with the surface Fe species coverage. This indicates an optimum coverage level where the rates of both the water dissociation step and the hydrogen formation step are balanced to achieve the highest efficiency. This multisite strategy assigns multiple reaction steps to different catalytic sites, and should also be extendable to other core/shell NPs to optimize their HER activity in alkaline media.

Heterostructured Electrocatalysts for Hydrogen Evolution Reaction Under Alkaline Conditions

“…Apart from Pt, other precious metals such as palladium and ruthenium have also been employed in heterostructured catalysts [ 40 , 41 ]. Xu et al fabricated a core-shell-structured Pd/FeO x (OH) 2−2 x composite by electrochemical cycling of the starting Pd/Fe 3 O 4 nanoparticles (Fig.…”

“…Xu et al fabricated a core-shell-structured Pd/FeO x (OH) 2−2 x composite by electrochemical cycling of the starting Pd/Fe 3 O 4 nanoparticles (Fig. 3 a–d) [ 40 ]. In this hybrid, the Fe species act as additional sites for water dissociation for improving the proton supply, and the Pd surface serves as the hydrogen adsorption/desorption sites (Fig.…”

“…g Turnover frequencies (TOFs) of Pd/FeO x (OH) 2−2 x NPs and catalysts in the benchmark literature: Pd/C, Pd-CN x , Ni-MoS 2 , and CoP. h HER activity versus FeO x (OH) 2−2 x coverage [ 40 ]. Copyright 2017, Wiley–VCH …”

Construction and Application of Interfacial Inorganic Nanostructures

“…(D) iR‐corrected linear sweep voltammogram (LSV) curves of Pd@FeO x (OH) 2–2 x NPs (collected in 0.1 M KOH). Reprinted with permission, [ 93 ] Copyright 2017, Wiley‐VCH.…”

Synthesis of PdP Nanoparticles as Electrocatalysts for Hydrogen Evolution Reaction in an Alkaline Medium

“…It is necessary to develop e±cient and relatively cheap HER catalysts under alkaline conditions. [24][25][26][27][28] The properties of Pd, which is in the same group as Pt in the periodic table, is similar to Pt in some cases. Previously, we reported that PdP NPs could catalyze the selective hydrogenation reaction of organic molecules.…”