Cobalt Phosphide Ultrathin and Freestanding Sheets Prepared through Microwave Chemical Vapor Deposition: A Highly Efficient Oxygen Evolution Reaction Catalyst

Abstract

The oxygen evolution reaction (OER) is the prime barrier for many appealing energy conversion and storage technologies, including water electrolysis, metal-air batteries, and fuel cells. Therefore, developing a cost-effective, efficient, and robust OER catalyst is still a challenge. Herein, we report a fast, low-cost, and gram-scale approach to overcome the synthesis of freestanding, ultrathin (ca. 1.3 nm), and mesoporous CoP sheets through the microwave-assisted growth of a cobalt-layered double hydroxide (Co-LDH) precursor coupled with chemical vapor deposition. The present 2D nanostructure not only guarantees a rich surface of active sites, but also promotes the charge and mass transfers due to the ultrathin and mesoporous features that allow it to efficiently perform the OER. It was found that the surface of the CoP sheets was oxidized in situ under the catalytic conditions, suggesting that Co 3 O 4 /CoP is effectively the active form of the catalyst, thereby modulating the electronic structure of Co atoms (active centers). This was embodied by the lowering of the Co-LDH's required overpotential to achieve 10 mA cm À 2 (η 10 ) from 296 to 265 mV and the Tafel slope decrease from 75 to 63 mV dec À 1 upon phosphorization. Such performances of CoP nanosheets are remarkably superior to those of commercial RuO 2 and compare favorably to the best values reported for noble-metal-free OER electrocatalysts.

A facile and simple microwave-assisted synthesis method for mesoporous ultrathin iron sulfide nanosheets as an efficient bifunctional electrocatalyst for overall water splitting

“…The high-frequency region of HER Nyquist plots shows a straight line or a distorted semi-circle, which might be recognized as due to the porous morphology of the catalyst. 58–61…”

“…The high-frequency region of HER Nyquist plots shows a straight line or a distorted semi-circle, which might be recognized as due to the porous morphology of the catalyst. [58][59][60][61] Furthermore, the 2D mesoporous and large surface area of Fe 3 S 4 supposedly provide unconfined surfaces and free spaces, which positively manipulate an increase in the elimination of liberated H 2 bubbles with the immediate circulation of the electrolyte to secure complete use of dynamic sites in the Fe 3 S 4 . To acquire a deeper understanding of resourcing the superior catalytic activity of Fe 3 S 4 , its real electrochemically active surface area (ECSA) was evaluated through electrochemical double-layer capacitance (C dl ), and this value suggested a relative estimation that is linearly proportionate to the ECSA.…”

Droplet Flow Assisted Electrocatalytic Oxidation of Selected Alcohols under Ambient Condition

“…Revealing electron transfer from Co atoms to P atoms in CoP sheets, suggesting a partial positive charge for Co centers and a partial negative charge for P centers [33]. This type of charge transfer facilitates the adsorption and desorption of intermediates and products during electrochemical oxidation of various substrates [34,35].…”

Synthesis of Ultrathin Porous Bimetallic Nickel–Cobalt Phosphide Nanosheets as an Excellent Bifunctional Electrocatalyst for Overall Water Splitting

“…Ni 2 P and CoP were prepared as reported in our previous work. [14,39] Detailed experimental work is illustrated in supporting information.…”

“…Because of this mass deviation in loaded mass, there is a deviation in over potential of overall water splitting to measure the overpotential of HER and OER. [14] The inside basis as the great bifunctional electrocatalytic kinetics of the NiCoP for primary reactions for overall water splitting with high activity as well as outstanding stability has a low thickness of NS 2.76 and 2.70 nm (Figure 3d,e), which produces additionally disclosed active sites, [59][60][61] surface roughness which is created because of etching, consequences of H 2 throughout the synthetic method of NiCoP NSs have enlarged the defects and supporting the mass to charge deportation in the catalytic procedure, [39] as well as porous morphology and large surface area (Figure 3g) further boosting the electrocatalytic kinetics and active sites that considerably improved the overall water splitting of NiCoP NS. [62][63][64][65]…”