Rational Construction of a N, F Co‐doped Mesoporous Cobalt Phosphate with Rich‐Oxygen Vacancies for Oxygen Evolution Reaction and Supercapacitors

Abstract

Transition‐metal phosphates have been widely applied as promising candidates for electrochemical energy storage and conversion. In this study, we report a simple method to prepare a N, F co‐doped mesoporous cobalt phosphate with rich‐oxygen vacancies by in‐situ pyrolysis of a Co‐phosphate precursor with NH4+ cations and F− anions. Due to this heteroatom doping, it could achieve a current density of 10 mA/cm2 at lower overpotential of 276 mV and smaller Tafel slope of 57.11 mV dec−1 on glassy carbon. Moreover, it could keep 92 % of initial current density for 35 h, indicating it has an excellent stability and durability. Furthermore, the optimal material applied in supercapacitor displays specific capacitance of 206.3 F g−1 at 1 A ⋅ g−1 and maintains cycling stability with 80 % after 3000 cycles. The excellent electrochemical properties should be attributed to N, F co‐doping into this Co‐based phosphate, which effectively modulates its electronic structure. In addition, its amorphous structure provides more active sites; moreover, its mesoporous structure should be beneficial to mass transfer and electrolyte diffusion.

N‐doped oxygen vacancy‐rich NiCo 2 O 4 nanoarrays for supercapacitor and non‐enzymatic glucose sensing

“…Additionally, doping with heteroatoms-such as N, P, and S atoms-could enhance the intrinsic electrochemical activity of bimetal oxides by modifying the electronic structure (M-O-N) to increase the reaction rate. 15,16 Moreover, when oxygen vacancy sites are substituted by N doping, the availability of active sites could be enhanced, thereby boosting the electron mobility and reaction rate. 15 In this way, N atoms doped into the bimetal oxide lattice could displace several O atom sites, resulting in increased oxygen defects.…”

“…Nevertheless, because of its low inherent electrical conductivity, the ability of the material to attain excellent electrochemical performance as an SC or biosensor device is constrained. A technique for controlling the redox sites on an electrode surface with a large surface area and numerous electrochemically active sites could be introduced to overcome these constraints 14,16,17 . First, oxygen vacancies could be induced by a thermal reduction in a high‐temperature environment, such as annealing 15 .…”

“…The chemical properties of the material could also be altered by controlling its electrical conductivity. Additionally, doping with heteroatoms—such as N, P, and S atoms—could enhance the intrinsic electrochemical activity of bimetal oxides by modifying the electronic structure (M‐O‐N) to increase the reaction rate 15,16 . Moreover, when oxygen vacancy sites are substituted by N doping, the availability of active sites could be enhanced, thereby boosting the electron mobility and reaction rate 15 .…”

“…A technique for controlling the redox sites on an electrode surface with a large surface area and numerous electrochemically active sites could be introduced to overcome these constraints. 14,16,17 First, oxygen vacancies could be induced by a thermal reduction in a high-temperature environment, such as annealing. 15 Second, the structural modification of the TMO spinel structure could be modified by doping with anionic ions.…”

Electrochemically Reconstructed Vanadic Oxide-Doped Cobalt Pyrophosphate as an Electrocatalyst for the Oxygen Evolution Reaction

“…On the one hand, to enhance the surface area and enrich the active site of catalysts, the engineering morphologies of cobalt pyrophosphate-based materials were studied systematically. − Other enormous efforts have also been made to develop cobalt phosphate/pyrophosphate materials with different morphologies such as porous, nanocage, nanobelts, and so on. On the other hand, the doping of heteroatoms was advantageous to improve the catalytic activity of OER catalysts through promoting electronic migration and electrical conductivity, or introducing rich-defects, such as the cationic-doped catalysts of Na 2 CoP 2 O 7 /rGO, K 2 Co 3 (P 2 O 7 ) 2 , Na 2 Ni 0.75 Fe 0.25 P 2 O 7 -nano, Na 2 MnP 2 O 7 pyrophosphate, and Co–Fe pyrophosphate nanosheets and the anionic-doped catalysts including N, C, F, and P dopants. ,− Therefore, the continued exploration of the synthetic and regulating strategies on pyrophosphate is of great significance for the development of efficient OER electrocatalysts.…”