Controlled Assembly of Cu/Co‐Oxide Beaded Nanoclusters on Thiolated Graphene Oxide Nanosheets for High‐Performance Oxygen Evolution Catalysts

Abstract

The use of water splitting modules is highly desired for the sustainable production of H2 as a future energy carrier. However, the sluggish kinetics and demand of high anodic potential are the bottlenecks for half‐the cell oxygen evolution reaction (OER), which severely hamper the overall conversion efficiency. Although transition metal oxides based electrocatalysts have been envisioned as cost‐effective and potential contenders for this quest, nevertheless, their low conductivity, instability, and limited number of active sites are among the common impediments that need to be addressed to eventually enhance their inherent catalytic potential for enhanced OER activity. Herein, the controlled assembly of transition metal oxides, that is, Cu@CuOx nanoclusters (NCs, ≈2 nm) and Co@CoOx beaded nanoclusters (BNCs, ≈2 nm), on thiol‐functionalized graphene oxide (G‐SH) nanosheets is reported to form novel and highly efficient electrocatalysts for OER. The thiol (‐SH) functionality was incorporated by selective epoxidation on the surface of graphene oxide (GO) to achieve chemically exfoliated nanosheets to enhance its conductivity and trapping ability for metal oxides in nanoscale dimensions (≈2 nm). During the electrocatalytic reaction, overpotentials of 290 mV and 310 mV are required to achieve a current density of 10 mA cm−2 for BNCs and NCs, respectively, and the catalysts exhibit tremendous long‐term stability (≈50 h) in purified alkaline medium (1 m KOH) with no dissolution in the electrolyte. Moreover, the smaller Tafel slopes (54 mV/dec for BNCs and 66 mV/dec for NCs), and a Faradic efficiency of approximately 96 % indicate not only the selectivity but also the tailored heterogeneous electrons transfer (HET) rate, which is required for fast electrode kinetics. It is anticipated that such ultrasmall metal oxide nanoclusters and their controlled assembly on a conducting surface (G‐SH) may offer high electrochemical accessibility and a plethora of active sites owing to the drastic decrease in dimensions and thus can synergistically ameliorate the challenging OER process.

Green synthesis of zinc oxide nanoparticles using Elaeagnus angustifolia L. leaf extracts and their multiple in vitro biological applications

“…NPs are conventionally prepared by various physical and chemical methods (microwave irradiation, ultrasonication, sol–gel, wet impregnation, laser-vaporization routes, etc. 7 – 9 . Conventional methods of synthesizing nanostructured materials are costly, utilize toxic reagents, require complicated procedures and expensive equipment, consume a large amount of energy and time, employ noxious reducing agents, and require organic solvents and non-biodegradable stabilization agents and are thus environmentally harmful.…”

Environmentally friendly green approach for the fabrication of silver oxide nanoparticles: Characterization and diverse biomedical applications

“…Metal oxide nanoparticles (MNPs) synthesized using green route are gaining attention due to their energy saving, safe, cost‐effective benign, and eco‐friendly nature (Hameed et al, 2019). MNPs significantly vary in size, shape, surface effect, magnetic, electrical, and optical properties compared to their bulk counterpart (Iqbal et al, 2018; Munir et al, 2019; Munir et al, 2020; Iqbal et al, 2020). Among the different MNPs studied, Ag 2 O nanoparticles have gained particular attention in nanomaterial research due to their unique properties and multifunctional nature.…”

Electronic and Structural Modification of Mn3O4 Nanosheets for Selective and Sustained Seawater Oxidation

“…The Gd-Mn 3 O 4 @CuO-Cu­(OH) 2 has a smaller Tafel value of 58 mV dec –1 compared to Gd-Mn 3 O 4 @Cu, Mn 3 O 4 @Cu, CuO-Cu­(OH) 2 , and IrO 2 , verifying its favorable OER kinetics. The lower Tafel slope value for heterostructure paraded a higher charge-transfer coefficient at interjection . It revealed that structural interaction between Mn 3 O 4 nanosheets and the CuO-Cu­(OH) 2 structure remarkably reduces the thermodynamic barrier for OER.…”

“…The lower Tafel slope value for heterostructure paraded a higher charge-transfer coefficient at interjection. 36 It revealed that structural interaction between Mn 3 O 4 nanosheets and the CuO-Cu(OH) 2 structure remarkably reduces the thermodynamic barrier for OER. The remarkable reduction in the Tafel slope value after surface oxygen vacancy creation and Gd doping indicate that this dual treatment optimized the chemisorption energy of active sites for OER intermediates adsorption and desorption.…”