Oxygen vacancies engineered self-supported B doped Co3O4 nanowires as an efficient multifunctional catalyst for electrochemical water splitting and hydrolysis of sodium borohydride

Borate Anion Dopant Inducing Oxygen Vacancies over Co3O4 Nanocages for Enhanced Oxygen Evolution

“…High-resolution Co 2p XPS spectra revealed that the intensity of the Co 3+ (795.22 eV) peak is significantly higher than that of Co 2+ (780.12 eV), and the ratio of Co 3+ /Co 2+ increased from 1.15 to 1.22, indicating that the low-valence Co 2+ is irreversibly oxidized to the high-valence Co 3+ during the OER process (Figure S20a and Table S3). Differently, B 1's signal peak completely disappeared after the OER (Figure S20b), which may be due to the fact that the B element on the catalyst surface dissolved into the electrolyte during the OER process under the high potential [31]. As shown in Figure S20d, the peaks of the metal-oxygen bond (M-O, 929.10 eV, vacant oxygen (Vo, 531.15 eV), and adsorbed oxygen (532.49 and 535.45 eV) are clearly observed after the OER.…”

“…The high-resolution N 1s XPS spectra (Figure 4e) can be deconvoluted into three peaks corresponding to the pyridine-N (399.0 eV) and pyrrolic-N (399.8 eV) [68]. As shown in Figure 4f, the high-resolution O 1s XPS spectra can be divided into four characteristic peaks, where the binding energy at 530.9 contributes to the lattice oxygen (M-O, OI), and the binding energy at 531.36 eV can be assigned to the oxygen vacancy (Vo, OII) [31]. The resultant B-Co3O4-1@ZIF-67 and B-Co3O4-2@ZIF-67 both have vacant oxygen (Vo, OII) peaks whereas Co(OH)2@ZIF-67 only contains two oxygen species of lattice oxygen (M-O, 530.74 eV) and adsorbed oxygen (OIII, 531.53 eV) (Figure S12f), proving that the introduction of boron leads to the formation of oxygen vacancy defects.…”

“…On one hand, the unique nanostructures, such as nanosheets and nanocages, usually possess large specific surface area, which are beneficial to the mass transport and exposure of catalytically active sites, and the release of the generated gas during the water splitting process [24,[27][28][29][30]. On the other hand, recent studies have shown that the introduction of dopants can induce the formation of a large number of oxygen vacancy defects, increasing electronic conductivity and promoting the improvement of electrochemical OER performance [31,32]. For instance, the introduction of boron into transition metal compounds was reported to induce vacancy defects and result in the generation of large numbers of catalytically active sites, promoting the improvement of electrochemical performances [24,31,33].…”

“…On the other hand, recent studies have shown that the introduction of dopants can induce the formation of a large number of oxygen vacancy defects, increasing electronic conductivity and promoting the improvement of electrochemical OER performance [31,32]. For instance, the introduction of boron into transition metal compounds was reported to induce vacancy defects and result in the generation of large numbers of catalytically active sites, promoting the improvement of electrochemical performances [24,31,33]. Based on the above considerations, it can be reasonable to conclude that high OER catalytic activity can be expected for heteroatom-doped Co 3 O 4 -based materials with nanocages structures composed of ultrathin nanosheets.…”

NiRu0.3Se Nanoparticles In Situ Grown on Reduced Graphene: Synthesis and Electrocatalytic Activity in the Oxygen Evolution Reaction

“…Avoiding the overlapping complexity of OER process with oxidation region of nickel, OER activity is evaluated by comparing overpotentials at current density of 20 mA cm À 2 . [35] The quantitative evaluation of OER activity shows that NiRu 0.3 Se/rGO required an overpotential (η 10 ) of 290 mV to produce oxygen at a current density of 10 mA cm À 2 (η = 1.52 V-1.23 V = 290 mV). Furthermore, the η of NiRu 0.2 Se/rGO and NiRu 0.1 Se/rGO is estimated to be 340 and 360 mV, respectively, to generate 10 mA cm À 2 .…”