Electron Density Modulation of Metallic MoO₂ by Ni Doping to Produce Excellent Hydrogen Evolution and Oxidation Activities in Acid

Abstract

Development of non-noble metal electrocatalysts for hydrogen evolution reaction (HER) and hydrogen oxidation reaction (HOR) in acid is a great challenge for the development of polymer electrolyte membrane water electrolysis (PEMWE) and polymer electrolyte membrane fuel cells (PEMFC). Here, we report an efficient strategy for modulating the electron density of MoO2 by Ni doping to accelerate HER and HOR in acid. This is particularly important for PEMWE, PEMFC, and regenerative fuel cells. X-ray absorption spectroscopy demonstrates that Ni is doped by replacing Mo atoms in MoO2. Then Ni doping can lead to electron deficiency on neighboring O sites, which are induced to adsorb hydrogen and then increase the surface hydrogen coverage. Therefore, the doping of Ni can modulate the electron density of MoO2 for accelerating HER and HOR. Our results indicate that the incorporation of a high-electronegativity transition metal into MoO2 provides a new strategy for replacing Pt as an electrocatalyst for HER and HOR in acid.

Rapid Synthesis of Various Electrocatalysts on Ni Foam Using a Universal and Facile Induction Heating Method for Efficient Water Splitting

“…[ 21 ] The high‐resolution Mo 3d signal of NiMoO 4 /NF‐IH in Figure 2k was divided into Mo 3d 5/2 (232.1 eV) and Mo 3d 3/2 (235.2 eV), showing the existence of high oxidation states Mo 6+ . [ 6b,22 ] The high‐resolution Ni 2p and Fe 2p spectra of NiFe LDH/NF‐IH are shown in Figure 2j,k, respectively. The two peaks of Ni 2p, Ni 2p 3/2 , and Ni 2p 1/2 , were located at 856.1 and 873.9 eV, respectively, along with their shake‐up satellite peaks at 861.8 and 880.1 eV.…”

“…[ 2a,b ] To reduce the reliance on noble metal‐based electrocatalysts, many efforts have been devoted to exploring earth‐abundant transition metal‐based electrocatalysts, including metal carbides, nitrides, oxides, phosphides, and sulfides. [ 3a,b ] Among them, Mo‐based electrocatalysts, such as MoS 2 , [ 4a–c ] Mo 2 C, [ 5a,b ] MoO 2 , [ 6a,b ] and MoNi alloy, [ 7a–c ] have attracted widespread attention due to superior electrocatalytic properties. For example, Feng and co‐workers [ 7b ] prepared a highly efficient MoNi 4 electrocatalyst by the pyrolysis of NiMoO 4 cuboids, which possessed a low overpotential of 15 mV and worked stably for 10 h at 10, 100, and 200 mA cm −2 , respectively.…”

“…Yu et al. [ 6b ] reported the synthesis of Ni and NiO nanoparticles decorated by amorphous MoOx nanorods (Ni/NiO/MoOx) nanocomposite on Ni foam (NF) by a hydrothermal treatment at 150 °C for 6 h, followed by an Ar‐protected annealing process at 400 °C for 2 h with a heating rate of 3 °C min −1 , which took about 12 h in the whole preparation process. The synthesis process had a slow heating and cooling rate basing on radiation mode, where the heat of the hot resistance wires radiated to the surface of the being heated object.…”

Defect Engineering of Molybdenum-Based Materials for Electrocatalysis

“…Other than Pd, other metal heteroatom doping could have a significant effect on electrocatalysts. For example, Zeng et al [7] designed a kind of Nidoped MoO2. In this study, density functional theory (DFT) calculations proved that Ni doping caused the lack of electrons around O atoms, and these electron-deficient sites increased the coverage of hydrogen on the catalyst surface.…”

“…Some of the prominent ones include water electrolytic technology [3], metal-air batteries [4,5], fuel cells [6], and ammonia synthesizing, involving crucial electrochemical reactions such as oxygen reduction/evolution, hydrogen oxidation/evolution, and the nitrogen reduction. However, one of the major obstacles to the practical applications is the rate of the electrochemical reactions involved [7]. Electrocatalysts play a key role in reducing the reaction kinetic barriers and promoting the efficiency and selectivity of the electrochemical reactions [8][9][10].…”