Porous N-Doped Carbon-Encapsulated CoNi Alloy Nanoparticles Derived from MOFs as Efficient Bifunctional Oxygen Electrocatalysts

Abstract

A porous N-doped carbon-encapsulated CoNi alloy nanoparticle composite (CoNi@N−C) was prepared using a bimetallic metal−organic framework composite as the precursor. The optimal prepared Co 1 Ni 1 @N−C material at 800 °C exhibited well-defined porosities, uniform CoNi alloy nanoparticle dispersion, a high doped-N level, and scattered CoNi−N x active sites, therefore affording excellent oxygen catalytic activities toward the reduction and evolution processes of oxygen. The oxygen reduction (ORR) onset potential (E onset ) on Co 1 Ni 1 @N−C was 0.91 V and the halfwave potential (E 1/2 ) was 0.82 V, very close to the parameters recorded on the Pt/C (20 wt Pt%) benchmark. Moreover, it is worth noting that the ORR stability of Co 1 Ni 1 @N−C was prominently higher than that of Pt/C. Under the oxygen evolution reaction condition, Co 1 Ni 1 @N−C generated the maximum current density at the potential of 1.7 V (8.60 mA cm −2 ) and the earliest E onset (1.35 V) among all Co x Ni y @N−C hybrids. The Co 1 Ni 1 @N−C catalyst exhibited the smallest ΔE value, confirming the superior bifunctional activity. The high surface area and porosity, and CoNi−N x active sites on the carbon surface including the proper interactions between the N-doped C shell and CoNi nanoparticles were attributed as the main contributors to the outstanding oxygen electrocatalytic property and good stability.

Enhanced Electrocatalytic Performance through Body Enrichment of Co‐Based Bimetallic Nanoparticles In Situ Embedded Porous N‐Doped Carbon Spheres

“…In detail, CoNi‐ e ‐PNC catalyst displays an excellent OER catalytic activity with a low onset potential of 1.41 V and a small overpotential of 0.24 V at 10 mA cm −2 (Figure a). Compared with previously reported CoNi‐based catalysts, CoNi‐ e ‐PNC catalyst exhibits competitive OER activity not only at low current density of 10 mA cm −2 , but also in terms of the high current densities at 50 and 100 mA cm −2 (Figure b) 1a,15,21. Meanwhile, CoNi‐ e ‐PNC catalyst also demonstrates the lowest Tafel slope (112 mV dec −1 , Figure S14a, Supporting Information) and the dramatically decreased charge transfer resistance (30.8 Ω, Figure c), revealing the accelerated kinetics of the electrode reactions and improved electron transfer ability at the interface of electrocatalyst and electrolyte .…”

“…High‐resolution transmission electron microscopy (HRTEM) images of CoM nanoparticles describe the cross‐links of two lattice fringes corresponding to the (111) planes of Co and M metal (Figure e, Figures S1–S3c, Supporting Information), revealing the formation of CoM alloys, whose atomic structures are intuitively presented in atomic configuration diagrams 10a,14. Notably, the difference of the interplanar spacing of Co (111) plane and the slight shift of (111) diffraction peaks in the X‐ray diffraction (XRD) patterns for CoM‐ e ‐PNC synchronously indicate the crystal deformation, which is inducted by transition metal M with different atomic radius entering the lattice of Co metal during alloying process (Figure S5a, Supporting Information) . High‐angle annular dark‐field scanning transmission electron microscopy (HAADF‐STEM) and corresponding mapping images (Figure f Figures S1–S3d, Supporting Information) display that C, N, Co, and M elements are evenly distributed over the entire CoM‐ e ‐PNC submicrospheres, and the characteristic signals of M and Co are fully overlapped, further demonstrating that CoM alloy nanoparticles are formed and highly dispersed on the NC support.…”

“…Similarly, the M 2p spectra show the presence of metallic M and M‐N species (Figure b–e), which confirm the formation of CoM and the coordination effect between M and melamine . Additionally, N 1s (Figure f and Figure S9, Supporting Information) and C 1s (Figure g and Figure S10, Supporting Information) spectra reveal N species are existed as two kinds of coupling of metal‐pyridinic N and CN bonds in CoM‐ e ‐PNC,5a,15 which can still be detected in the Raman and Fourier transform infrared (FT‐IR) spectra of Co‐ e ‐PNC and CoM‐ e ‐PNC (Figure S11, Supporting Information). Encouragingly, all the samples present the high integral intensity ratio ( I G / I D ) with the appearance of 2D peaks, suggests that the unique porous N‐doped carbon support provides an excellent 3D conductive network…”

Hydroxylated high-entropy alloy as highly efficient catalyst for electrochemical oxygen evolution reaction

“…Oxygen evolution reaction (OER), a half reaction involved in electrochemical water splitting, CO 2 reduction, and metal-air batteries, restricts the efficiency of these energy conversion systems due to sluggish reaction kinetics [1,2]. To accelerate OER, highly efficient electrocatalysts are required.…”

Trimetallic Nanoparticles Encapsulated into Bamboo‐Like N‐Doped Carbon Nanotubes as a Robust Catalyst for Efficient Oxygen Evolution Electrocatalysis

“…al used bimetallic MOFs composite as the precursor to prepare the porous N-doped carbon encapsulated CoNi alloy nanoparticle composite (CoNi@NÀ C). [30] Although various Ndoped CNTs (NCNTs) structures derived from MOFs have been reported as OER electrocatalysts, the electrochemical activity of most of them still need improvement. [31][32][33] In this study, we focused on improving the catalytic performance of the catalyst by adjusting the electronic structure and encapsulating the active nanoparticles in the N-doped carbon nanotube to significantly boost electrochemical performance and stability.…”