Herein, a novel in-situ “atomic binding to heterointerface” strategy is proposed to obtain Co 2 P/ [email protected] /CNTs catalyst with abundant heterointerface between cobalt phosphide and tungsten carbide (Co 2 P/WC) by the polyoxometalates (POMs)-based metal–organic frameworks (MOFs) precursor. The natural quasi interfaces in K 10 [Co 4 (H 2 O) 2 (PW 9 O 34 ) 2 ] molecule crucially guide the abundant Co 2 P/WC heterointerfaces down to atomic level. Meanwhile, MOFs cages can effectively encapsulate nanosized POMs at molecular level to control the size and dispersion of Co 2 P/WC nanoparticle , while carbon nanotubes (CNTs) enhance conductivity at nanoscale level. The interfacial electronic modulation between Co 2 P and WC lowering the energy barrier of the rate determining step , thus Co 2 P/ [email protected] /CNTs showed reasonable hydrogen evolution reaction (HER) activity and stability in all-pH media including sea water. This work provides a “bottom-up” synthetic strategy for confined heterostructures , thus offering the prospect for more efficient interfacial charge modulation.
Ya Gao,Zhongling Lang,Feiyang Yu,Huaqiao Tan,Gang Yan,Yonghui Wang,Yuanyuan Ma,Yangguang Li
The hydrogen evolution reaction (HER) produces clean hydrogen through an electrochemical process. However, new nonprecious-metal electrocatalysts for the HER are required to reduce the consumption of energy. Herein, we report a new Co 2 P/WC nano-heterojunction that consists of Co 2 P and WC composite phases coated with a few-layer N-doped graphitic carbon shells (Co 2 P/WC@NC). The composite was prepared by a one-step annealing of the polyoxometalate Na 9 (NH 4 ) 5 [{(B-α-PW 9 O 34 )Co 3 (OH)(H 2 O) 2 (Ale)} 2 Co]⋅35 H 2 O (Co 7 P 6 W 18 ) and dicyandiamide (DCA). The preparation method consisted of the simultaneous phosphorization of Co and carbonization of W in a confined space to isolate a Co 2 P/WC nano-heterojunction phase for the first time. Co 2 P/WC@NC facilitated the generation of hydrogen in the electrolysis process, which had an overpotential of only 91 mV at a current density of 10 mA cm −2 in the acid solution; an excellent HER performance (2 H + +2 e − →H 2 ) and Tafel slope (40 mV dec −1 ) as well as durability over a period of 50 h were achieved. Theoretical calculations showed that the Co 2 P, WC, and N pyridinic C dopants in the material synergistically promoted the HER activity rather than the individual constituents. Furthermore, Co 2 P/WC@NC nano-heterojunctions showed good HER performance in the whole pH range of electrolytes and considerable durability in acidic media containing transition metal ions, which may attract more attention for the exploration and optimization of nano-heterojunction catalysts for the HER. Graphical Acids and Bases don′t matter : A Co 2 P/WC nano-heterojunction consisting of cobalt phosphide and tungsten carbide composite phases coated with a few-layer N-doped graphitic carbon shells (Co 2 P/WC@NC) exhibits excellent activity toward the hydrogen evolution reaction over the whole pH range. Theoretical calculations show that the Co 2 P, WC, and N pyridinic C dopants in the material synergistically promote the HER activity.
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