Bi-functional Oxygen Electrocatalysts Using Mixed-Metal Tungsten-Nitrides in Alkaline Media

Abstract

Transition metal-tungsten nitrides (CrWN2, MnWN2, FeWN2, Co3W3N, Ni2W3N) could be synthesized and electrocatalytic properties on electrochemical oxygen reduction and evolution reactions were examined. The oxygen reduction performance was in the order of Co3W3N > MnWN2 > Ni2W3N >> FeWN2 >> CrWN2. while the oxygen evolution was in that of Co3W3N >> CrWN2 > Ni2W3N > MnWN2 >> FeWN2. Then, the Co3W3N gave high bi-functional oxygen electrocatalytic properties. Furthermore, Ni-doped (Co1-xNix)3W3N (x = 0 -1.0) were prepared and it was found that the (Co0.6Ni0.4)3W3N gave the highest bi-functional electrocatalytic properties. The cathode performance was achieved with the electrode containing 32 wt% (Co0.6Ni0.4)3W3N, i. e., the current density as high as 280 mA cm -2 , which was 10 times higher than that of a carbon-only electrode, was obtained at (0.80 V vs. RHE) in 5 mol L -1 KOH at 70 °C. Also, the (Co0.6Ni0.4)3W3N electrode showed high activity to oxygen evolution as high as 300 mA cm -2 at (1.60 V vs. RHE). As it was observed the changes in binding energy at O1s, N1s, W4f, Co2p, and Ni2p spectra among Co3W3N, (Co0.6Ni0.4)3W3N, and Ni2W3N by X-ray photoelectron spectroscopy, the change in electrical properties at the surface of the nitrides should be one of the reasons of the high performance.

Unveiling the ligand-mediated phase engineering mechanism in two-dimensional transition metal chalcogenides through coordination geometry control

“…40 The W 4f XPS spectrum of W(CO) 6 : OLAm-200 (Fig. S12 †) in connection with the Raman result implies W 6− species (37.1 and 35.0 eV) 41 by forming W-NH 2 bonds. Similarly, the spectrum of W(CO) 6 : TOPO-200 exhibits W 6+ doublet peaks (37.5 and 35.6 eV) contributed by W-O]P bonds.…”