Abstract
Electrochemical hydrogen evolution reactions (HER) have drawn tremendous interest for the scalable and sustainable conversion of renewable electricity to clear hydrogen fuel. However, the sluggish kinetics of the water dissociation step severely restricts the high production of hydrogen in alkaline media. Tuning the electronic structure by doping is an effective method to boost water dissociation in alkaline solutions. In this study, N-doped CoO nanowire arrays (N-CoO) were designed and prepared using a simple method. X-ray diffraction (XRD), element mappings and X-ray photoelectron spectroscopy (XPS) demonstrated that N was successfully incorporated into the lattice of CoO. The XPS of Co 2p and O 1s suggested that the electronic structure of CoO was obviously modulated after the incorporation of N, which improved the adsorption and activation of water molecules. The energy barriers obtained from the Arrhenius relationship of the current density at different temperatures indicated that the N-CoO nanowire arrays accelerated the water dissociation in the HER process. As a result, the N-CoO nanowire arrays showed an excellent performance of HER in alkaline condition. At a current density of 10 mA cm−1, the N-CoO nanowire arrays needed only a 123 mV potential, which was much lower than that of CoO (285 mV). This simple design strategy provides some new inspiration to promote water dissociation for HER in alkaline solutions at the atomic level.
Highlights
Due to severe environmental pollution as a result of the excessive consumption of traditional fossil fuels [1,2,3,4], it is desirable to explore clean and sustainable energy sources [5,6]
To assess the energy barriers, we studied the effect of temperature on the performance of the CoO and N-CoO nanowire arrays and found the rate constants followed the Arrhenius relationship
We have demonstrated that the incorporation of N in CoO nanowires can effectively improve the hydrogen evolution reactions (HER) performance in an alkaline solution
Summary
Due to severe environmental pollution as a result of the excessive consumption of traditional fossil fuels [1,2,3,4], it is desirable to explore clean and sustainable energy sources [5,6]. FFiigguurree 11isisththeescshcehmemataictiiclliullsutrsattriaotniofnorfothrethpereppraerpatairoantioofnthoef CthoeOCaonOd Nan-CdoNO-CnaonOonwaniroewairreraayrsr.ayBsr.ieBfrlyie,fltyh,ethCeoCOoaOnadnNd -NC-oCOoOnannaonwowireireararraryasyswweerereoobbttaainineeddbbyy aannnneeaalliinngg tthhee pprreeccuurrssoorr ooff tthhee CCooxx((OOHH))yy nnaannoowwiirreeaarrrraayyssuunnddeerr AArr aanndd NNHH33 aattmmoosspphheerreess,, rreessppeecc-ttiivveellyy ((ffoorr ddeettaaiillss,, sseeee EExxppeerriimmeenntt)). The peak positions of Co 2p3/2 and Co 2p1/2 in N-CoO were higher Catalysts 2021, 11, x FOR PEER REVtIhEaWn those in CoO, suggesting that the N incorporation could effectively tune the electr5onoifc structure of Co. Figure 2e, f reveal the O 1s spectra of the CoO and N-CoO nanowire arrays. The overpotential and Tafe slope of the N-CoO nanowire arrays (123 mV, 97 mV dec−1) were still far from the state-of-the-art Pt/C catalyst (49 mv, 41 mV dec−1), this design strategy provides a simple method to promote water dissociation in alkaline solutions at the atomic level. The significantly decreased electrochemical activation energy of N-CoO for HER was consistent with our XPS analysis, which showed that the N-CoO nanowire arrays could boost water dissociation.
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