Oxygen-Inserted Top-Surface Layers of Ni for Boosting Alkaline Hydrogen Oxidation Electrocatalysis

Abstract

Precisely tailoring the electronic structures of electrocatalysts to achieve an optimum hydroxide binding energy (OHBE) is vital to the alkaline hydrogen oxidation reaction (HOR). As a promising alternative to the Pt-group metals, considerable efforts have been devoted to exploring highly efficient Ni-based catalysts for alkaline HOR. However, their performances still lack practical competitiveness. Herein, based on insights from the molecular orbital theory and the Hammer–Nørskov d-band model, we propose an ingenious surface oxygen insertion strategy to precisely tailor the electronic structures of Ni electrocatalysts, simultaneously increasing the degree of energy-level alignment between the adsorbed hydroxide (*OH) states and surface Ni d-band and decreasing the degree of anti-bonding filling, which leads to an optimal OHBE. Through the pyrolysis procedure mediated by a metal–organic framework at a low temperature under a reducing atmosphere, the obtained oxygen-inserted two atomic-layer Ni shell-modified Ni metal core nanoparticle (Ni@Oi-Ni) exhibits a remarkable alkaline HOR performance with a record mass activity of 85.63 mA mg–1, which is 40-fold higher than that of the freshly synthesized Ni catalyst. Combining CO stripping experiments with ab initio calculations, we further reveal a linear relationship between the OHBE and the content of inserted oxygen, which thus results in a volcano-type correlation between the OH binding strength and alkaline HOR activity. This work indicates that the oxygen insertion into the top-surface layers is an efficient strategy to regulate the coordination environment and electronic structure of Ni catalysts and identifies the dominate role of OH binding strength in alkaline HOR.

Metastable Metal–Alloy Interface in RuNi Nanoplates Boosts Highly Efficient Hydrogen Electrocatalysis

“…As two key reactions for achieving hydrogen recycling, HER and HOR involve the same key intermediates (H*), where the hydrogen adsorption free energy (Δ G H *) is widely used to evaluate the performance of HER and HOR. − Considering the cost and abundance, the transition metal nickel (Ni) shows promising catalytic properties in half-reactions (HER and HOR), yet its Δ G H * is relatively high. − The construction of Ni-based alloy structures can effectively optimize Δ G H * and thus improve performance. Normally, Ni nanocrystals can crystallize in two lattice forms: the metastable phase and the stable phase.…”

Promoting Methane Dry Reforming over Ni Catalysts via Modulating Surface Electronic Structures of BN Supports by Doping Carbon

“…The interplanar distance of Ni/BN displays the standard spacing of Ni(111) (2.03 Å). The larger (2.19 Å) and smaller (1.82–1.86 Å) interplanar distances between Ni atoms are measured in the Ni particle of Ni/BCN catalysts, suggesting that the lattice expansion and shrink happens . Therefore, partial lattice expansion and shrink would cause the lattice distortion, resulting in the defects on the Ni surface.…”

“…Figure 2a that the lattice expansion and shrink happens. 43 Therefore, partial lattice expansion and shrink would cause the lattice distortion, resulting in the defects on the Ni surface. The EELS spectra of the B, C, and N K-edge at positions #1 and #3 without the location of Ni in Figure 2a,b shows in Figure 2c.…”

The Role of Hydroxide Binding Energy in Alkaline Hydrogen Oxidation Reaction Kinetics on RuCr Nanosheet†

“…[ 7‐9 ] Unfortunately, the kinetics of anodic hydrogen oxidation reaction (HOR) in alkaline electrolyte is much slower than that in acidic electrolyte. [ 10‐12 ] Therefore, understanding the mechanism and developing highly efficient electrocatalysts for alkaline HOR are highly desirable.…”