Activity Promotion of Core and Shell in Multifunctional Core–Shell Co₂P@NC Electrocatalyst by Secondary Metal Doping for Water Electrolysis and Zn‐Air Batteries

Abstract

Developing cost‐efficient multifunctional electrocatalysts is highly critical for the integrated electrochemical energy‐conversion systems such as water electrolysis based on hydrogen/oxygen evolution reactions (HER/OER) and metal‐air batteries based on OER/oxygen reduction reactions (ORR). The core–shell structured materials with transition metal phosphide as the core and nitrogen‐doped carbon (NC) as the shell have been known as promising HER electrocatalysts. However, their oxygen‐related electrocatalytic activities still remain unsatisfactory, which severely limits their further applications. Herein an effective strategy to improve the core and shell performances of core–shell Co2P@NC electrocatalysts through secondary metal (e.g., Fe, Ni, Mo, Al, Mn) doping (termed M‐Co2P@M‐N‐C) is reported. The as‐synthesized M‐Co2P@M‐N‐C electrocatalysts show multifunctional HER/OER/ORR activities and good integrated capabilities for overall water splitting and Zn‐air batteries. Among the M‐Co2P@M‐N‐C catalysts, Fe‐Co2P@Fe‐N‐C electrocatalyst exhibits the best catalytic activities, which is closely related to the configuration of highly active species (Fe‐doping Co2P core and Fe‐N‐C shell) and their subtle synergy, and a stable carbon shell for outstanding durability. Combination of electrochemical‐based in situ Fourier transform infrared spectroscopy with extensive experimental investigation provides deep insights into the origin of the activity and the underlying electrocatalytic mechanisms at the molecular level.

Exploiting the Multifunctionality of M2+/Imidazole–Etidronates for Proton Conductivity (Zn2+) and Electrocatalysis (Co2+, Ni2+) toward the HER, OER, and ORR

“…In addition, the homogeneous distribution of the metal ions indicates the formation of solid solutions for the bimetallic compositions ( Figures S16 and S17 ). This metal ion distribution differs from that reported elsewhere, 29 in which doping metal ions are dispersed throughout both the metal phosphide nanoparticles and the graphitic substrate.…”

“…Comparatively, CoL@800 displayed lower performance, which may be attributed to a lower concentration of the CoP phase ( Table 2 ), which in turn may be influenced by the material history and the lack of the SAL, i.e., the absence of N in the carbon matrix. 29 …”

“…To evaluate the electrochemical capability of the prepared catalysts, CoLIm-0@800 was selected as the working electrode owing to its remarkable electrocatalytic properties toward the OER, ORR, and HER, comparable to other high-performance cobalt materials. 64 − 66 Its bifunctional activity for electrochemical oxygen cycle (e.g., zinc–air battery) in alkaline electrolytes is highlighted, as the potential difference (Δ E = E j =10 – E 1/2 ) 29 between OER and ORR calculated for this electrode material, 0.74 V, is comparable to the values for the Pt/C (Δ E = 0.83 V) and the RuO 2 (Δ E = 1.04 V) benchmark electrocatalysts.…”

“… 27 Τhe N-doping strategy influences the carbon shell on these materials. 28 However, N-doped TMPs generally exhibit poor electrochemical activity toward the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) due to the lack of active sites, 29 presumably in the carbon shell, which precludes the access to multifunctional TMP electrocatalysts. Recently, electrocatalysts derived from ETID have been investigated toward the OER, ORR, and HER.…”

Progress in In Situ Research on Dynamic Surface Reconstruction of Electrocatalysts for Oxygen Evolution Reaction

“…The vibration and rotation of sample molecules lead to the change of dipole moment, resulting vibration and rotation energy levels from ground state to excited state in the transition of molecular. [ 130–133 ] The intensity of transmitted light in the absorption region is reduced to obtain the molecular absorption spectrum. In the in situ FTIR of internal reflection mode, a nanogold film with surface enhancement effect is chemically or vacuum plated on monocrystalline silicon (Si), and an electrocatalyst is dripped or electrodeposited on the nanogold film substrate as the working electrode.…”