CoO_x(OH)_y/C nanocomposites in situ derived from Na₄Co₃(PO₄)₂P₂O₇ as sustainable electrocatalysts for water splitting

Abstract

An original electrode design strategy for water splitting was considered. Electrodes covered by CoOx(OH)y/C nanocomposites were in situ fabricated. Assembled CoO(OH)/C∥Co(OH)2/C system reveals excellent long-time stability (more than 50 hours at 10 mA cm−2) with the total overpotential of 0.6 V.

Boosting H2 Generation Coupled with Selective Oxidation of Methanol into Value‐Added Chemical over Cobalt Hydroxide@Hydroxysulfide Nanosheets Electrocatalysts

“…In the case of Co(OH) 2 @HOS/CP electrode, a cell voltage of 1.631 V is needed to achieve the current density of 10 mA cm −2 in 1 m KOH in the absence of methanol. In fact, this potential is lower than those of recently reported Co‐based electrodes for overall water splitting, such as cobalt nitridevanadium oxynitride nanohybrid (1.64 V for 10 mA cm −2 ), cobalt iron hydroxide (1.64 V for 10 mA cm −2 ), 3D Co(OH) 2 @NCNTs@NF (1.72 V for 10 mA cm −2 ), Co(OH) 2 –Au–Ni(OH) 2 (1.75 V for 10 mA cm −2 ), and CoO x (OH) y /C nanocomposites (1.80 V for 10 mA cm −2 ) . Interestingly, the LSV curve of MFO coupled with HER dramatically shifts to more negative potentials, and the cell voltage is reduced to 1.497 V at the current density of 10 mA cm −2 , suggesting much better energy conversion efficiency by replacing OER with MFO.…”

“…In fact, this potential is lower than those of recently reported Co-based electrodes for overall water splitting, such as cobalt nitridevanadium oxynitride nanohybrid (1.64 V for 10 mA cm −2 ), [53] cobalt iron hydroxide (1.64 V for 10 mA cm −2 ), [54] 3D Co(OH) 2 @ NCNTs@NF (1.72 V for 10 mA cm −2 ), [55] Co(OH) 2 -Au-Ni(OH) 2 (1.75 V for 10 mA cm −2 ), [56] and CoO x (OH) y /C nanocomposites (1.80 V for 10 mA cm −2 ). [57] Interestingly, the LSV curve of MFO coupled with HER dramatically shifts to more negative potentials, and the cell voltage is reduced to 1.497 V at the current density of 10 mA cm −2 , suggesting much better energy conversion efficiency by replacing OER with MFO. More importantly, the current density of Co(OH) 2 @HOS/CP is 70 mA cm −2 at 1.66 V, which is 4.78 times higher than that of conventional water splitting (HER and OER), indicating the boosting of hydrogen generation.…”

A Cobalt‐Based Amorphous Bifunctional Electrocatalysts for Water‐Splitting Evolved from a Single‐Source Lazulite Cobalt Phosphate

“…Subsequently, surfactant‐assisted Co‐OH‐HPi nanosheets were investigated for OER and the large surface area as well as PCET process with different proton acceptors (OH − and HPO 4 2− ) found to be crucial for superior electrocatalytic activity . On the contrary, a complete dissolution of phosphorous from Na 4 Co 3 (PO 4 ) 2 P 2 O 7 leading to crystalline β‐Co(OH) 2 and CoO(OH) for HER and OER was reported by Odynets et al Moreover, Cobo et al successfully developed a Janus cobalt‐based electrocatalyst that forms metallic cobalt coated with a cobalt‐oxo/hydroxo‐phosphate layer to promote HER and under anodic conditions, it switches into amorphous cobalt oxide to catalyze OER . Recently, Co‐P materials containing mixed Co phosphide/Co phosphate as well as Co‐P encapsulated in N, P‐codoped mesoporous carbon networks were also designed by electrodeposition for bifunctional OER and HER .…”

Insights into Transition Metal Phosphate Materials for Efficient Electrocatalysis

“…Therefore, through chemical or electrochemical transformation of metal phosphate, the active catalytic materials such as Co(OH) 2 and CoO(OH) (for HER and OER, respectively) can be directly formed during electrolysis. [123] Encapsulating transition metal phosphate inside carbons to construct integrated electrocatalyst could improve the catalytic activity and stability in harsh conditions. Co phosphate nanoparticles embedded in 3D porous N,P-co-doped carbons were synthesized by in situ potentiostatic electropolymerization of aniline and phytic acid on carbon cloth.…”