Iron covalent doping in WB2 to boost its hydrogen evolution activity

Fig. 1 (a) The fabrication process of Fe covalent-doped WB2 (donated as FeWB2) catalyst. (b) The SEM image of Fe-WB2. (c) The TEM image of Fe-WB2, the inset in (c) shows the SAED pattern and HRTEM of Fe-WB2. (d) The XRD patterns of WB2 and Fe-WB2 catalyst. (e)-(h) The TEM-EDS elemental mapping images of Fe-WB2. Colour code: green, B; gray, W; yellow, Fe; white, H; red, oxygen.Fig. 2 XPS survey spectrum of (a) Fe-WB2. High-resolution XPS spectra in (b)Fe 2p (c) W 4f, and (d) B 1s regionsFig.3 (a) Polarization curves of Fe-WB2, WB2, CC and Pt/C for the HER in 0.5 M H2SO4 with 95% IR-correction. (b) Corresponding Tafel plot of Fe-WB2, WB2, CC and Pt/C for the HER. (c) Nyquist plots of Fe-WB2 and WB2 catalysts. (d) Long time-dependent current density curve.Fig. 4 The calculated ΔGH* values of HER at the different sites on the (a) FeWB2 (001) (b) WB2 (001) surface. (c) Projected crystal orbital Hamilton population (pCOHP) between W and Nads on Fe-WB2 (001) and WB2 (001). (d)Free energy diagram for NRR at U = 0 V on the Fe-WB2 (001). Colour code: green, B; dark gray, W; yellow, Fe; blue, N; pink, H.Fig. 5 (a) The linear sweep voltammetric (LSV) curves of Fe-WB2 and WB2 catalysts were measured in N2-saturated and Ar-saturated 0.05 M H2SO4 electrolyte. (b) Chronoamperometric results at different applied potentials.(c) Production rate of ammonia and FEs at different applied potential. (d) Cycling test for the stability of NRR.