Salt-Templated Nanoarchitectonics of CoSe2-NC Nanosheets as an Efficient Bifunctional Oxygen Electrocatalyst for Water Splitting

Abstract

Recently, the extensive research of efficient bifunctional electrocatalysts (oxygen evolution reaction (OER) and hydrogen evolution reaction (HER)) on water splitting has drawn increasing attention. Herein, a salt-template strategy is prepared to synthesize nitrogen-doped carbon nanosheets encapsulated with dispersed CoSe2 nanoparticles (CoSe2-NC NSs), while the thickness of CoSe2-NC NSs is only about 3.6 nm. Profiting from the ultrathin morphology, large surface area, and promising electrical conductivity, the CoSe2-NC NSs exhibited excellent electrocatalytic of 10 mA·cm−2 current density at small overpotentials of 247 mV for OER and 75 mV for HER. Not only does the nitrogen-doped carbon matrix effectively avoid self-aggregation of CoSe2 nanoparticles, but it also prevents the corrosion of CoSe2 from electrolytes and shows favorable durability after long-term stability tests. Furthermore, an overall water-splitting system delivers a current density of 10 mA·cm−2 at a voltage of 1.54 V with resultants being both the cathode and anode catalyst in alkaline solutions. This work provides a new way to synthesize efficient and nonprecious bifunctional electrocatalysts for water splitting.

MOF-Derived Cobalt@Mesoporous Carbon as Electrocatalysts for Oxygen Evolution Reaction: Impact of Organic Linker

“…The calculated I D / I G values were 1.11, 1.00, 0.97, and 0.87 for Co/NMC-2MeIM, Co/NMC-PDCA, Co/NMC-BDC-NH 2 , and Co/MC-DHTA, respectively. The higher I D / I G value of Co/NMC-2MeIM indicated the presence of a higher density of defects, increasing the adsorption capacity sites, which provides a higher number of catalytically active sites for OER compared to other Co/MC electrocatalysts. , …”

“…It is noteworthy that Raman spectra provide an evaluation of the graphitization and defect degrees of materials . The Raman spectra of as-prepared materials (Figure ) show peaks at 1336 and 1594 cm –1 , which correspond to the disordered A 1 g mode for the disordered sp 3 carbon (D band) and the E 2 g vibrational mode of the graphite sp 2 carbon (G band), respectively. ,, The value of I D / I G is commonly used to evaluate the degree of carbon disorder. , The I D / I G ratio usually increases with increasing nitrogen doping levels in carbon nanostructures due to the production of additional vacancies and structural flaws caused by nitrogen substitution .…”

“…43 This was demonstrated by Cao et al, who revealed that CoSe 2 -NC NSs exhibited a higher degree of defects (I D /I G = 1.63) compared to CoSe 2 -NC NPs (I D /I G = 1.26), leading to a superior OER performance (η 10 = 246.7 mV, Tafel = 72.66 mV dec −1 ). 43 Based on the above-mentioned discussions and our electrocatalytic investigations, the superior performance of Co/NMC-2MeIM can be assigned to the following factors: (i) the high specific surface area of Co/NMC-2MeIM compared to other investigated electrocatalysts, which could promote more active and adsorption sites. (ii) The high content of Co 3+ is important for OH* and OOH* adsorption sites, thus promoting electron storage and transfer between those oxygen species and the active sites.…”

“…It is noteworthy that Raman spectra provide an evaluation of the graphitization and defect degrees of materials. 43 The Raman spectra of as-prepared materials (Figure 5) show peaks at 1336 and 1594 cm −1 , which correspond to the disordered A 1g mode for the disordered sp 3 carbon (D band) and the E 2g vibrational mode of the graphite sp 2 carbon (G band), respectively. 35,44,45 The value of I D /I G is commonly used to evaluate the degree of carbon disorder.…”

“…The higher I D / I G value of Co/NMC-2MeIM indicated the presence of a higher density of defects, increasing the adsorption capacity sites, which provides a higher number of catalytically active sites for OER compared to other Co/MC electrocatalysts. 43,48 To get deep insights into the chemical states of the elements involved in the investigated electrocatalysts, an X-ray photoelectron spectroscopy (XPS) investigation was performed. As depicted in Figure 6a, the XPS survey spectrum of Co/NMC-2MeIM electrocatalyst reveals the peaks of Co, C, O, and N elements (for survey spectrum of other Co/MC materials, see Figure S3) which is consistent with the results of EDX spectra.…”