High‐Performance Bifunctional Porous Iron‐Rich Phosphide/Nickel Nitride Heterostructures for Alkaline Seawater Splitting

Abstract

Seawater is the most abundant natural water resource in the world, which is an inexhaustible and low‐cost feedstock for hydrogen production by alkaline water electrolysis. It is appearling to develop robust and stable electrocatalysts for alkaline seawater electrolysis. However, the development of seawater electrolysis is seriously impeded by anodic chloride corrosion and chlorine evolution reaction, and few non‐noble electrocatalysts show prominent catalytic performance and excellent durability. Here, a heterogeneous electrocatalyst constructed by in situ growing highly dispersed iron‐rich bimetallic phosphide nanoparticles on metallic Ni3N (Fe2−2xCo2xP/Ni3N), which exhibits outstanding bifunctional catalytic activities for alkaline seawater splitting, is reported. The optimal (Fe0.74Co0.26)2P/Ni3N and Fe2P/Ni3N electrocatalysts demand only 113 and 212 mV to afford 100 mA cm−2 for hydrogen and oxygen evolution reactions (HER and OER) in 1 m KOH, respectively, thus substantially expediting overall water/seawater electrolysis at 100 mA cm−2 with 1.592/1.645 V. Particularly, Fe2P/Ni3N displays an unprecedented overpotential of 302 mV at 500 mA cm−2, which represents the best alkaline seawater oxygen evolution activity among the ever‐reported non‐noble electrocatalysts; and thus substantially expedites overall water/seawater splitting at 500 mA cm−2 with 1.701/1.768 V, surpassing most of the reported non‐noble lectrocatalysts. This work provides a new approach for developing high‐performance electrocatalysts for seawater splitting.

Hierarchical Cobalt–Nickel Phosphide/Molybdenum Disulfide Hybrid Electrocatalyst Triggering Efficient Hydrogen Generation in a Wider pH Range

“…The synthesis of CoP/Ni 2 P/MoS 2 −CC is illustrated in Scheme 1, which contains hydrothermal, electrodeposition, and annealing steps. 44,45 Moreover, the peaks of Ni 2p 1/2 and Ni 2p 3/2 for Ni−O are located at 876.1 and 858.1 eV. 46 In Figure 2c, three obvious peaks at 232.7, 229.5, and 226.6 eV are attributed to Mo 3d 3/2 , Mo 3d 5/2 , and S 2s of the CoP/Ni 2 P/MoS 2 −CC sample.…”

“…2b), the peaks located at 871.2 and 854.5 eV are the responses of Ni 2p 1/2 and Ni 2p 3/2 spectra for Ni−P, while the peaks at 881.9 and 861.8 eV are the signals of the satellite peaks. 44,45 Moreover, the peaks of Ni 2p 1/2 and Ni 2p 3/2 for Ni−O are located at 876.1 and 858.1 eV. 46 In Figure 2c, three obvious peaks at 232.7, 229.5, and 226.6 eV are attributed to Mo 3d 3/2 , Mo 3d 5/2 , and S 2s of the CoP/Ni 2 P/MoS 2 −CC sample.…”

“…The two peaks at 793.75 and 779.09 eV are Co 2p 1/2 and Co 2p 3/2 in the XPS spectra of Co 2p for Co–P, and another two peaks at 799.5 and 783.1 eV are the responses of Co 2p 1/2 and Co 2p 3/2 for Co–O. − In addition, the satellite peaks of Co 2p are located at 805.0 and 786.8 eV. In Ni 2p spectra of CoP/Ni 2 P/MoS 2 –CC (Figure b), the peaks located at 871.2 and 854.5 eV are the responses of Ni 2p 1/2 and Ni 2p 3/2 spectra for Ni–P, while the peaks at 881.9 and 861.8 eV are the signals of the satellite peaks. , Moreover, the peaks of Ni 2p 1/2 and Ni 2p 3/2 for Ni–O are located at 876.1 and 858.1 eV . In Figure c, three obvious peaks at 232.7, 229.5, and 226.6 eV are attributed to Mo 3d 3/2 , Mo 3d 5/2 , and S 2s of the CoP/Ni 2 P/MoS 2 –CC sample .…”

Fabricating Ru Atom-Doped Novel FeP4/Fe2PO5 Heterogeneous Interface for Overall Water Splitting in Alkaline Environment

“…As shown in Figure 2b, the binding energies at 463.0 and 485.3 eV should be attributed to Ru 3p 3/2 and Ru 3p 1/2 orbitals of the oxidation state of Ru. 50 For the Fe 2p spectrum (Figure 2c), the fitted peaks at 705.6 and 718.4 eV declare the presence of Fe−P bonds in Ru@FeP 4 /Fe 2 PO 5 , 28,30,32 which is shifted forward with respect to the FeP 4 /Fe 2 PO 5 catalyst (704.7 and 718.3 eV). Similarly, the fitted peaks at 711.8 and 725.9 eV are attributed to the Fe−O bond of the FeP 4 /Fe 2 PO 5 catalysts.…”

“…In recent decades, transition metal materials (TMM) have attracted widespread attention as bifunctional catalysts. − Due to the advantages of high active area and effective reduction of reaction activation energy with d -orbital electrons, transition metal oxides (TMO), − sulfides (TMS), nitrides (TMN), − and phosphides (TMP) − are reported for water splitting. Notably, the construction of heterogeneous interfaces in TMM systems has become an important strategy for promoting the EWS process because the electronic structure could be optimized at the interfaces, largely accelerating the charge transfer and conductivity for HER and OER. − Moreover, the heterogeneous structure of phosphides/phosphates plays an important role in the OER process. − Ren et al have used the heat treatment method to construct Fe­(PO 3 ) 2 /Ni 2 P heterogeneous interface catalysts that exhibited 265 mV low overpotential catalytic performance at industrial current density of 500 mA cm –2 .…”