FeCoP₂ Nanoparticles Embedded in N and P Co-doped Hierarchically Porous Carbon for Efficient Electrocatalytic Water Splitting

Abstract

The design and synthesis of low-cost and efficient bifunctional electrocatalysts for water splitting are critical and challenging. Hereby, a bimetallic phosphide embedded in a N and P co-doped porous carbon (FeCoP2@NPPC) material was synthesized by using sustainable biomass-derived N- and P-containing carbohydrates and non-noble metal salts as precursors. The obtained material exhibits good catalytic activities in hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and overall water splitting. The bimetallic alloy phosphide (FeCoP2) is the active site for electrocatalysis. Theoretical calculation indicates that the sub-layer Fe atoms and top-layer Co atoms in FeCoP2 exhibit a synergistic effect for enhanced electrocatalytic performance. The carbon matrix around the FeCoP2 can prevent the corrosion during the catalytic reactions. The hierarchically porous structure of the FeCoP2@NPPC material can promote the transfer of electrons and electrolyte, and increase the contact area of the active sites and electrolytes. N- and P-containing functionalities improve the wetting and conductivity properties of the porous carbon. Due to the synergistic effects, FeCoP2@NPPC requires a low overpotential of 114 and 150 mV at the current density of 10 mA cm–2 for HER in 0.5 M H2SO4 and 1.0 M KOH, and an overpotential of 236 mV for OER in 1.0 M KOH solution, which are much lower than those of FeP@NPPC and CoP@NPPC. Based on the density functional theory calculation, FeCoP2 yields the smallest Gibbs free energy change of rate-determining step among the samples, which leads to better electrochemical performances. In addition, when FeCoP2@NPPC was used as a bifunctional catalyst in water splitting, the electrolyzer needed a low voltage of 1.60 V to deliver the current density of 10 mA cm–2. Furthermore, this work provides a strategy for preparing sustainable, stable, and highly active electrocatalysts for water splitting.

Nonmetallic Active Sites on Nickel Phosphide in Oxygen Evolution Reaction

“…Transition metals with partially filled d orbitals are generally the active catalytic sites in OER [ 16 , 17 , 21 , 64 ]. Recently, it has been reported that nonmetal atoms may become the active sites for catalytic reactions in theoretical studies [ 63 , 64 , 65 ].…”

“…Therefore, the development of high-performance and low-cost catalysts is highly desirable. Recently, cheap transition metal oxides [ 14 , 15 ], phosphides [ 16 , 17 , 18 , 19 ], nitrides [ 20 ], sulfides [ 21 , 22 , 23 , 24 ], carbides [ 25 ], etc., have been studied as emerging electrocatalysts, and many show excellent OER catalytic activity.…”

AlP-regulated phosphorus vacancies over Ni–P compounds promoting efficient and durable hydrogen generation in acidic media

“…S6 and Table S1†). Besides, the HER performance of P V -np-Ni(Al)-40 electrode exceeds some previously reported catalysts such as FeP nanosheet/Ti ( η 10 = 79 mV), 42 RuP 2 /NPC ( η 10 = 59 mV), 43 FeCoP 2 @NPPC ( η 10 = 114 mV), 44 and CoP/CN/Ni ( η 10 = 66 mV) 45 (Table S2†).…”

Hollow CoP Encapsulated in an N-Doped Carbon Nanocage as an Efficient Bifunctional Electrocatalyst for Overall Water Splitting

“…EIS was performed to record the Nyquist plots in Figure 5d to reflect the charge-transfer ability at the electrode/electrolyte interface in the electrochemical reaction. 52 Fitting by an equivalent circuit, the h-CoP@NC-700-300, h-CoP@NC-800-300, and s-CoP@NC-900-300 showed charge-transfer resistances (R ct ) of 29.96, 36.25, and 33.45 Ω, respectively (Table S3). The R ct of h-CoP@NC-900-300 was 26.72 Ω, which was lower than the ones above, proving its fast charge-transfer ability.…”