Co–Pyridinic-N Bond Constructed at the Interface of Co_xP and N-Doped Carbon to Effectively Facilitate Oxygen Reduction

Abstract

The construction of bonding interfaces between cobalt-base phosphides and N-doped carbon is considered an effective means to promote ORR catalytic performance. However, the role of different nitrogen configurations in promoting the ORR performance of cobalt-base phosphides is currently unknown. Herein, the honeycomb-like Co x P@N-doped carbon catalyst was constructed to systematically investigate the effect of different nitrogen configurations on improving the catalytic performance of Co x P. Systematic experimental investigations and density functional theory (DFT) calculations indicate that the interaction of Co with pyridinic-N not only regulates the atomic Co coordination environment but also induces strong orbital hybridization between N-p orbitals and Co-d orbitals, significantly increasing the electron density on pyridinic-N sites, which greatly increases the attraction to oxygen-containing intermediates and lowers the reaction energy barrier, thus promoting the catalytic activity for ORR. Furthermore, honeycomb morphology not only reduces the internal diffusion resistance of reactants and products as well as the relative concentration of surface reactants but also exposes more accessible active sites and increases the contact area with the electrolyte, thus greatly enhancing the oxygen reduction reaction. As expected, the asprepared catalyst exhibits ultrahigh ORR activity with a half-wave potential of 0.88 V, which is superior to that of the noble metal Pt and most previously reported non-noble metal catalysts. This study perfectly explains why cobalt-base phosphide embedded in Ndoped carbon can improve its ORR catalytic performance.

Carbon-Layer-Protected CoP/Carbon Nanosheets as Highly Durable Bifunctional Electrocatalysts for Rechargeable Zinc–Air Batteries

“…Recently, transition-metal phosphides-based carbon (TMPs/C) composites, such as the nanohybrid of TMP nanoparticles (NPs) distributed on a C support, have emerged rapidly as a promising alternative to expensive noble-metal-based electrocatalysts, exhibiting significant bifunctional activity for both OER and ORR in ZABs and a distinct economical advantage. , In this case, the phosphorus and metal sites in TMPs not only act as active sites (e.g., proton acceptor and oxygenated intermediate acceptor) during the electrocatalytic process but also facilitate charge transfer due to the higher electrical conductivity of phosphides than their oxide counterparts. , The nanocomposites composed of TMP NPs and a heteroatom-doped C support demonstrated excellent electrocatalytic performance and good stability in a tough medium with a wide pH range, attributed to their polytropic composition/structures. − Nonetheless, the synthesis of performance TMPs/C composites still suffers from the coalescence and subsequent poor dispersion of NPs during pyrolysis, which can severely reduce the site density as well as activity of the as-prepared electrocatalysts. , Moreover, the naked TMPs dispersing on the C matrix are subject to poor durability under harsh electrochemical conditions, , for example, acidic/alkaline media at high voltages. Therefore, the development of a TMPs/C electrocatalyst with both high activity and durability for ZABs is of critical importance.…”

“…7−14 Recently, transition-metal phosphides-based carbon (TMPs/ C) composites, such as the nanohybrid of TMP nanoparticles (NPs) distributed on a C support, have emerged rapidly as a promising alternative to expensive noble-metal-based electrocatalysts, exhibiting significant bifunctional activity for both OER and ORR in ZABs and a distinct economical advantage. 15,16 In this case, the phosphorus and metal sites in TMPs not only act as active sites (e.g., proton acceptor and oxygenated intermediate acceptor) during the electrocatalytic process but also facilitate charge transfer due to the higher electrical conductivity of phosphides than their oxide counterparts. 16,17 The nanocomposites composed of TMP NPs and a heteroatom-doped C support demonstrated excellent electrocatalytic performance and good stability in a tough medium with a wide pH range, attributed to their polytropic composition/structures.…”

“…15,16 In this case, the phosphorus and metal sites in TMPs not only act as active sites (e.g., proton acceptor and oxygenated intermediate acceptor) during the electrocatalytic process but also facilitate charge transfer due to the higher electrical conductivity of phosphides than their oxide counterparts. 16,17 The nanocomposites composed of TMP NPs and a heteroatom-doped C support demonstrated excellent electrocatalytic performance and good stability in a tough medium with a wide pH range, attributed to their polytropic composition/structures. 17−20 Nonetheless, the synthesis of performance TMPs/C composites still suffers from the coalescence and subsequent poor dispersion of NPs during pyrolysis, which can severely reduce the site density as well as activity of the as-prepared electrocatalysts.…”

N/P-Codoped Carbon Nanotubes for Efficient Oxygen Reduction Reaction

“…Both the Zn–air battery (ZAB) and fuel cells are seen as promising new clean energy and energy conversion devices with low pollution and high energy density. Oxygen reduction reactions (ORRs) are a vital process in fuel cells and ZAB. − Whereas, the slow ORR process hinders the commercialization of fuel cells and ZAB, thus limiting their future development. − Therefore, there is an immediate requirement for high-performance catalysts to augment the kinetics and efficiency of the ORR process. So far, platinum and its alloys are regarded as the premier catalysts due to their exceptional catalytic activity. − Nevertheless, the widespread application of platinum and its alloy catalysts is limited by factors such as low reserves, weak toxicity resistance, high cost, and low stability. − Moreover, the previous catalyst preparation methods are often complex and low-productivity and cannot meet the requirements of large-scale production. , Therefore, there has been a lot of interest in exploring ORR catalysts with cost-effectiveness, high toxicity resistance, high stability, and an easy manufacturing process to solve the above problems.…”