Phase-dependent hydrogen evolution activity of nickel phosphide nanosheet arrays in alkaline electrolytes

Experimental and Theoretical Insights into Transition-Metal (Mo, Fe) Codoping in a Bifunctional Nickel Phosphide Microsphere Catalyst for Enhanced Overall Water Splitting

“…The binding energies of the observed peaks were calibrated using the C 1s binding energy of 284.5 eV . The Ni 2p core-level spectra (Figure a) of the films show two peaks at 856 and 873.6 eV along with two shakeup satellites, which can be assigned to the Ni 2p 3/2 and Ni 2p 1/2 peaks of Ni 3 P, respectively. , Figure b depicts the high-resolution Mo 3d spectra for the Ni 3 P:Mo and Ni 3 P:FeMo samples; the peaks at 232.2 and 235.7 eV were assigned to Mo 3d 5/2 and Mo 3d 3/2 , respectively, which could have stemmed from the surface oxidation of MoP to MoO 3 upon exposure to air . The Fe 2p core-level spectra (Figure c) were deconvoluted into Fe 2p 3/2 and Fe 2p 1/2 peaks along with their satellite peaks, confirming that Fe mostly exists in the Fe 3+ oxidation state in the Ni 3 P:Fe and Ni 3 P:FeMo samples.…”

“…To date, various inexpensive earth-abundant catalysts have been explored as possible alternatives to noble-metal catalysts, including transitional metal oxides/hydroxides, − sulfides, − selenides, , and phosphides. − Among them, although transition-metal phosphides (TMPs) are promising due to their efficient catalytic performances, durability, and cost-effectiveness, − they still suffer from inferior catalytic performance and stability compared to noble-metal catalysts. To solve this, the reaction energy barrier for HER and OER of metal-phosphide-based catalysts needs to be optimized by improving the electron transfer during electrocatalysis and modifying their electronic structure via doping. − A previous theoretical study showed that nickel phosphide (Ni 3 P) can achieve a very low Gibbs free energy (Δ G H* ) level via structural and compositional engineering and by doping with Mo, Fe, and/or Co. − Thus, Δ G H* is a useful parameter for predicting the theoretical activity of catalysts: an ideal electrocatalyst should possess a low Δ G H* . − …”

Nickel sulfide and phosphide electrocatalysts for hydrogen evolution reaction: challenges and future perspectives

“…11c ). Kim et al 110 employed more phosphorus-rich phases of nickel phosphides and investigated Ni 2 P, Ni 5 P 4 , and NiP 2 in 1.0 M NaOH. The LSV curves showed that NiP 2 with lower needed overpotentials than other electrocatalysts was the most active phase ( Fig.…”

“…Thus, the stability of nickel phosphides improves with an increase in phosphorus content in their structure due to their lower compositional changes. In another work, Kim et al 110 compared the stability of NiP 2 and Ni 2 P in 1.0 M NaOH. The chronoamperometry test showed that NiP 2 had better stability than Ni 2 P ( Fig.…”

Recent Advances in Ni‐Based Electrocatalysts for Hydrogen Evolution Reaction

“…Kim's group synthesized self‐standing nickel phosphide nanosheet arrays of different crystal phases (Ni 2 P, Ni 5 P 4 , or NiP 2 ) on graphite through a hydrothermal process and thermal phosphidation reaction with controlled amounts and types of P sources (NaH 2 PO 2 and RP) (Figure 6g). [ 60 ] By comparing the morphologies of the nickel phosphides, it is found whether RP or NaH 2 PO 2 is used as the P source, and the morphology of the Ni precursors can be maintained after the phosphidation process (Figure 6h–k). In addition, the electrocalalytic activity of different nickel phosphides toward HER in alkaline follows the order of NiP 2 > Ni 5 P 4 > Ni 2 P (Figure 6i), which is consistent with previously reported studies.…”