In Situ Filling of the Oxygen Vacancies with Dual Heteroatoms in Co3O4 for Efficient Overall Water Splitting

Abstract

Electrocatalytic water splitting is a crucial area in sustainable energy development, and the development of highly efficient bifunctional catalysts that exhibit activity toward both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is of paramount importance. Co3O4 is a promising candidate catalyst, owing to the variable valence of Co, which can be exploited to enhance the bifunctional catalytic activity of HER and OER through rational adjustments of the electronic structure of Co atoms. In this study, we employed a plasma-etching strategy in combination with an in situ filling of heteroatoms to etch the surface of Co3O4, creating abundant oxygen vacancies, while simultaneously filling them with nitrogen and sulfur heteroatoms. The resulting N/S-VO-Co3O4 exhibited favorable bifunctional activity for alkaline electrocatalytic water splitting, with significantly enhanced HER and OER catalytic activity compared to pristine Co3O4. In an alkaline overall water-splitting simulated electrolytic cell, N/S-VO-Co3O4 || N/S-VO-Co3O4 showed excellent overall water splitting catalytic activity, comparable to noble metal benchmark catalysts Pt/C || IrO2, and demonstrated superior long-term catalytic stability. Additionally, the combination of in situ Raman spectroscopy with other ex situ characterizations provided further insight into the reasons behind the enhanced catalyst performance achieved through the in situ incorporation of N and S heteroatoms. This study presents a facile strategy for fabricating highly efficient cobalt-based spinel electrocatalysts incorporated with double heteroatoms for alkaline electrocatalytic monolithic water splitting.

Flexible Bifunctional Electrode for Alkaline Water Splitting with Long-Term Stability

“…As compared with other materials available in the literature (see Table S5, in SI), our bifunctional NiO -1.0 @CNTR electrode exhibited a promising OWS potential ( E 10 of ∼1.81 V), with the minimal loading of the NiO QD catalyst (≈83 μg/cm 2 only), which is comparable to the E 10 values reported in other single (transition) metal-based bifunctional catalysts with at least 1 order of magnitude higher “catalyst loading”, ,,,− ,− such as NiO nanosheets (NSs) on a nickel foam or NF ( E 3 > 1.8 V with a loading of 0.53 mg/cm 2 ), α-NiOOH NSs on NF ( E 4 > 1.75 V with 0.74 mg/cm 2 loading), NiO/GC on NF ( E 10 ∼ 1.7 V with 2 mg/cm 2 loading), NiO x -AC on carbon paper or CP ( E 10 ∼ 1.69 V with 2 mg/cm 2 loading), Ni­(OH) 2 NSs on NF ( E 10 ∼ 1.82 V), Co 3 O 4 nanocrystals (NCs) on carbon fiber paper or CFP (1.91 V with 0.35 mg/cm 2 loading), Ni 0.5 Se||Ni 0.75 Se NCs on CP (1.73 V with 0.6 mg/cm 2 loading), W-Ni 12 P 5 on carbon cloth or CC (1.73 V), CoP NCs on CC (1.75 V with 2 mg/cm 2 loading), and CoP NPs on NF (1.75 V with ∼1.2 mg/cm 2 loading) Figure c presents a graphical comparison of the “ E 10 ” values for various bifunctional electrocatalysts reported in the past literature as a function of the respective “catalyst loading”.…”

“…Besides, configuring the electrolyzer cell with the same materials for both electrodes (cathode and anode) would help to avoid the complexity of using different electrodes for HER and OER and unwanted “contamination” of electrodes and electrolytes. A comparative study ,− ,,,,,,− of current (or potential) retention over time, as reported in a previous literature, is shown in Figure e, which indicates the superior nature of our electrodes in terms of long-standing stability for OWS application.…”

Ag Nanoparticles and Rod-Shaped AgCl Decorated Porous PEDOT as a Bifunctional Material for Hydrogen Evolution Catalyst and Supercapacitor Electrode

“…The semicircular responds to the electron transfer restriction process, and a larger part means a resistance. The linear part corresponds to the diffusion restriction process [46,5 The values of Rs and Rct have been shown in Table 2. In a 1 mol NaOH solution values of PEDOT, PEDOT-Ag-0.005, and PEDOT-Ag/AgCl-0.05 are 1.69, 1.80, and respectively.…”

“…The existing rare fossil fuel environment will thus accelerate energy transition from fossil fuels to clean energy sources, such as hydrogen, solar energy, and bioenergy. The most direct and simple method for industrial production of pure hydrogen is electrocatalytic water splitting [1][2][3][4][5]. During the electrolysis of water, hydrogen evolution reactions (HER) and oxygen evolution reactions (OER) take place at different poles [6][7][8][9].…”

Carbonaceous Material Modified MoO2 Nanospheres with Oxygen Vacancies for Enhanced Visible-Light Photocatalytic Oxidative Coupling of Benzylamine

“…In comparison, surface OVs play an important role not only in the extension of the photo response, but also in increasing the charge separation efficiency [ 27 , 28 , 29 ]. Semiconductor photocatalysts with rich surface OVs, such as TiO 2 , BiO 2 , MoO 3 , WO 3 , ZnO and so on, have been extensively reported [ 16 , 30 , 31 , 32 , 33 ]. BiOCl nanosheets with surface OVs resulted in abundant surface low-coordinated Bi atoms, contributing to the assembly of O 2 molecules on the surface of photocatalyst [ 34 ].…”