Rational Engineering Co_xO_y Nanosheets via Phosphorous and Sulfur Dual‐Coupling for Enhancing Water Splitting and Zn–Air Battery

Abstract

Herein, an efficient multifunctional catalyst based on phosphorus and sulfur dual‐doped cobalt oxide nanosheets supported by Cu@CuS nanowires is developed for water splitting and Zn–air batteries. The formation of such a unique heterostructure not only enhances the number and type of electroactive sites, but also leads to modulated electronic structure, which produces reasonable adsorption energy toward the reactant, thereby improving electrocatalytic efficiency. The catalyst demonstrates small overpotentials of 116 and 280 mA cm−2 to achieve 10 mA cm−2 for hydrogen and oxygen evolution, respectively. As a result, a developed electrolyzer displays a cell voltage of 1.52 V at 10 mA cm−2 and long‐term stability with a current response of 92.3% after operating for 30 h. Moreover, using such a catalyst in the fabrication of a Zn–air battery also leads to a cell voltage of 1.383 V, along with a power density of 130 mW cm−2 at 220 mA cm−2.

Multifunctional Nickel–Cobalt Phosphates for High-Performance Hydrogen Gas Batteries and Self-Powered Water Splitting

“…Figure a reveals that the Ni 2p XPS spectra can be deconvoluted into two distinct spin–orbit doublet peaks and two dithered satellites, where the binding energies of Ni 2p 1/2 and Ni 2p 3/2 are observed at 873.50 and 855.85 eV, respectively, in good agreement with the electronic state of Ni 2+ Figure b shows the peaks at 798.28 and 782.23 eV that belong to the Co 2p 1/2 and Co 2p 3/2 peaks of the Co 2+ valence state, respectively; while the peaks at 796.22 and 780.80 eV belong to the Co 2p 1/2 and Co 2p 3/2 peaks of the Co 3+ valence state, respectively . In addition, the presence of two accompanying weak satellite peaks (803.59 and 786.33 eV) further confirms the simultaneous presence of Co 2+ and Co 3+ valence states. , As Figure c shows, the peak at 133.04 eV in the spectrum of P 2p is the characteristic peak of PO 4 3– , indicating that the phosphorus species are doped into the material in the form of PO 4 3– , helping to increase the activity of the NCP .…”

“…Figure 2a 46 Figure 2b shows the peaks at 798.28 and 782.23 eV that belong to the Co 2p 1/2 and Co 2p 3/2 peaks of the Co 2+ valence state, respectively; while the peaks at 796.22 and 780.80 eV belong to the Co 2p 1/2 and Co 2p 3/2 peaks of the Co 3+ valence state, respectively. 47 In addition, the presence of two accompanying weak satellite peaks (803.59 and 786.33 eV) further confirms the simultaneous presence of Co 2+ and Co 3+ valence states. 33,48 As Figure 2c shows, the peak at 133.04 eV in the spectrum of P 2p is the characteristic peak of PO 4…”

Co/MoC Nanoparticles Embedded in Carbon Nanoboxes as Robust Trifunctional Electrocatalysts for a Zn–Air Battery and Water Electrocatalysis

“…The charge-transfer resistance could be measured by the electrochemical impedance spectroscopy (EIS). Nyquist plots shown in Figure d reveal the smallest diameter of the semicircles for the Co@IC/MoC@PC catalyst, indicating its best charge-transfer behavior for ORR. , Next, to investigate the origins of the fast kinetics and striking ORR catalytic activity of Co@IC/MoC@PC, ultraviolet photoelectron spectroscopy was employed to evaluate the electron-donating abilities of the samples. As obviously seen in Figure , the Co@IC/MoC@PC catalyst shows an expected valence band maximum value of 0.13 eV, close to the Fermi level ( E F , set to 0 eV) and lower than 0.19 eV of Co@IC, implying that the exposed surfaces of Co@IC/MoC@PC nanocomposites possess more metallic character with higher density of states around E F . − Not surprisingly, the calculated working function of the Co@IC/MoC@PC is expected to be 4.19 eV, smaller than that of Co@IC catalyst.…”

“…With the increasingly serious energy gaps and environmental pollution, rechargeable metal–air battery and electrocatalytic overall water splitting (EOWS) have gradually attracted strong research interest due to their expected advantages such as high capacity, sustainability, and environmental friendliness and are therefore hailed as ideal and efficient energy conversion and storage technologies. − The core processes of these two catalytic systems mainly depend on three half-reactions, i.e ., hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and oxygen reduction reaction (ORR). − However, these reactions usually involve multiple-electron transfer processes, thus leading to slow kinetics and high overpotentials. − Although the uses of precious metal-based materials can improve these reaction efficiencies ( i.e ., Pt/C only for the ORR and HER, IrO 2 and RuO 2 only for the OER), their earth scarcity, high cost, and insufficient catalytic functions (single/dual catalytic functions) inevitably hinder the widespread technological applications. − Thus, the development of trifunctional electrocatalysts based on the earth-abundant nonprecious metals that can synchronously enhance the electrocatalytic efficiencies toward OER, HER, and OER is extremely paramount yet challenging. − …”

Material design and surface chemistry for advanced rechargeable zinc–air batteries

“…For example, Doan et al developed P, S dual-doped cobalt oxide nanosheets supported by Cu@CuS nanowires (P, S-Co x O y /Cu@CuS NWs). 85 They fabricated highly conductive materials using the heterostructures of Cu@CuS nanowires and cobalt oxide. The morphology of the P, S-Co x O y /Cu@CuS is shown in Fig.…”