Homologous CoP/NiCoP Heterostructure on N‐Doped Carbon for Highly Efficient and pH‐Universal Hydrogen Evolution Electrocatalysis

Abstract

Hydrogen evolution electrocatalysts can achieve sustainable hydrogen production via electrocatalytic water splitting; however, designing highly active and stable noble‐metal‐free hydrogen evolution electrocatalysts that perform as efficiently as Pt catalysts over a wide pH range is a challenging task. Herein, a new 2D cobalt phosphide/nickelcobalt phosphide (CoP/NiCoP) hybrid nanosheet network is proposed, supported on an N‐doped carbon (NC) matrix as a highly efficient and durable pH‐universal hydrogen evolution reaction (HER) electrocatalyst. It is derived from topological transformation of corresponding layer double hydroxides and graphitic carbon nitride. This 2D CoP/NiCoP/NC catalyst exhibits versatile HER electroactivity with very low overpotentials of 75, 60, and 123 mV in 1 m KOH, 0.5 m H2SO4, and 1 m PBS electrolytes, respectively, delivering a current density of 10 mA cm−2 for HER. Such impressive HER performance of the hybrid electrocatalyst is mainly attributed to the collective effects of electronic structure engineering, strong interfacial coupling between CoP and NiCoP in heterojunction, an enlarged surface area/exposed catalytic active sites due to the 2D morphology, and conductive NC support. This method is believed to provide a basis for the development of efficient 2D electrode materials with various electrochemical applications.

Large‐Size, Porous, Ultrathin NiCoP Nanosheets for Efficient Electro/Photocatalytic Water Splitting

“…Electrochemical measurement results (Figure 5d) reveal that bimetallic NiCoP nanosheets exhibit superior both HER (Figure S12, Supporting Information) and OER performance (Figure S13, Supporting Information) as compared with single‐phase Ni 2 P and CoP, indicating the synergistic effect between the Ni and Co owing to alloying. [ 15,16 ] Moreover, the NiCoP shows much larger electrochemical double‐layer capacitance than Ni 2 P and CoP (Figure S14, Supporting Information), further suggesting the excellent electrocatalytic activity of the NiCoP nanosheets. As displayed in Figure 5e, only negligible degradation is observed for NiCoP‐8.0 nanosheets after the long‐term cycling test of over 5000 cycles.…”

“…[ 9–14 ] The catalytic activity of transition metal phosphide is due to a moderate interaction between phosphorus and the reaction intermediate to form a suitable surface structure as a proton acceptor site. [ 15–17 ] However, single‐phase metal phosphides suffer from an inferior catalytic performance compared with noble metal catalysts. Recently, bimetallic transition‐metal phosphide Ni x Co y P z has attracted considerable attention owing to its superior catalytic properties for HER and OER to single‐phase transition‐metal phosphides (Ni 2 P and CoP), in which high positive charge of the Co and Ni atoms significantly enhances the acceptance sites of the hydride ions.…”

CoP/N‐Doped Carbon Nanowire Derived from Co‐Based Coordination Polymer as Efficient Electrocatalyst toward Oxygen Evolution Reaction

“…The additional two peaks at 786.3 and 802.9 eV were indexed to the shake‐up satellite . The P 2p spectrum of Figure d can be divided into three peaks, assigned to P 2p 3/2 (129.2 eV), P 2p 1/2 (130.0 eV), and oxidized P species (133.8 eV) . The peaks obtained at 782.0, 798.2, and 133.8 eV may be due to the unavoidable oxidation of the CoP surface during the acid‐washing process.…”

“…[39,40] The P 2p spectrum of Figure 3d can be divided into three peaks, assigned to P 2p 3/2 (129.2 eV), P 2p 1/2 (130.0 eV), and oxidized P species (133.8 eV). [41] The peaks obtained at 782.0, 798.2, and 133.8 eV may be due to the unavoidable oxidation of the CoP surface during the acid-washing process. The O 1 s spectrum in Figure S7b, Supporting Information, can again confirm the result.…”

Hydrogen Evolution Reaction - From Single Crystal to Single Atom Catalysts

“…Novel HER active supported transition metal pnictides and carbides also include bimetallic phosphide, Ni2-xCoxP supported on electrospun N-doped carbon nanofibers [115], CoP/NiCoP supported on N-doped carbon [116], Mo nitrides supported by B,N co-doped carbon nanotubes [117], MoC-MoP/N-doped carbon nanofibers [118], Ni-Co phosphide supported on Ni foam [119], biphase Ni5P4/NiP2 grown on Ni foam [120], Co2P/CoMoPx supported on Ni foam [121], NixCoyP supported on TiO2 [4], coupled Mo2C and Ni nanoparticles, encapsulated in porous carbon nanofibers [122], Ni2P/Cu3P on carbon paper [123], N-doped carbon coated MoP nanowires [124], CeO2-CoP-C hybrid nanostructure [125], Co6W6C nanocrystals anchored on N-doped carbon nanofibers [126], FeOOH/Ni3N [127], carbon supported CoP nanoparticles, with focus on size-dependent activity [128], Fe, Co and Ni phosphides anchored on metal-caged graphitic carbon [129], MoC2-doped NiFe alloy nanoparticles encapsulated with N-doped graphene [130], C3N4@MoN [131], CoP nanowires coupled with CoMoP nanosheets [132], Ni-Fe-P nanoparticle embedded in N-doped carbon supported on Ni foam [133], and Co, Al doped Fe2N/Fe3N [134].…”