Directly Anchoring Highly Dispersed Copper Sites on Nitrogen‐Doped Carbon for Enhanced Oxygen Reduction Electrocatalysis

Abstract

A simple but efficient post-treatment strategy was developed to directly anchor highly active and dispersed copper sites on N/C for enhanced oxygen reduction reaction (ORR) electrocatalysis. The ORR activity and selectivity of the prepared CuÀN/C catalyst were significantly enhanced due to efficient binding of copper ions with nitrogen groups on the carbon skeleton to form highly active CuÀN sites. Moreover, the prepared CuÀN/C catalyst also exhibited excellent stability in alkaline electrolytes and Zn-air batteries, indicating great potential for energy applications.Developing cheap and efficient non-platinum group metal (non-PGM) electrocatalysts for oxygen reduction reaction (ORR) is highly desired for large-scale fabrication and application of next-generation ORR-involved sustainable energy devices, including fuel cell, metal-air battery, and chlor-alkali industry. [1,2] In the last decade, transition metal and nitrogen-co-doped nanocarbon (TMÀN/C) materials have been fabricated successfully and thus are promising candidates for replacing PGM materials toward efficient oxygen reduction electrocatalysis. [3][4][5][6] Doping nitrogen atoms into a carbon skeleton can change its intrinsic electronic structures, which then activates the inert conjugated p electrons to be active for ORR. [7,8] Furthermore, when transition metal and nitrogen atoms exist simultaneously during synthesis, highly active metal sites coordinated with nitrogen atoms (TM-N x ) on carbon matrix can be formed and thus significantly boost the ORR electrocatalytic performance of the derived catalyst through strong synergetic effects with nitrogen-doped sites. [9][10][11] However, conventional synthesis paths inevitably generate large-sized metal nanoparticles (NPs), making it difficult to distinguish the contributions from different types of metal sites as well as maximize the use of metal atoms.Recently, highly dispersed metal catalysts, especially singleatom catalysts (SACs) with singly dispersed and isolated metal sites on a support, has drawn much attention. [12,13] SACs not only can maximize the utilization of metal atoms, but also minimize the side reaction due to the homogeneity of metal active sites. Such unique catalysts with highly dispersed metal sites offer great potential for achieving high activity and selectivity, as well as identifying the active sites and revealing the catalytic mechanism for ORR on non-PGM materials. [14] Therefore, the controllable construction of TMÀN/C materials with highly dispersed TM-based sites on carbon matrix is a promising way to significantly improve their electrocatalytic properties for ORR. Y. Li et al. reported a metal-organic-framework (MOF)-based synthesis strategy for Co-based ORR SACs, in which Co-N 2 sites with a strong interaction with peroxide showed superior activity to Co-N 4 sites and Co NPs. [15] Furthermore, an MOF-based cage-encapsulated-precursor pyrolysis strategy was developed to fabricate Fe-based ORR SACs, the electrocatalytic performance of which outperformed commercial Pt/C a...

Underpotential Deposition of Copper Clusters on Sulfur and Nitrogen Co‐Doped Graphite Foam for the Oxygen Reduction Reaction

“…The ORR pathway can also be examined by RRDE voltammetry via monitoring the intermediate peroxide species (Figure S20). [46][47][48] Compared with Cu NPs and SNGF, the Cu clusters/SNGF has a lower peroxide yield (6 %) and a higher value of n (3.9) (Figure 3c and S21b) which are in consistent with those obtained from KÀ L plots. The superior activity of Cu clusters/SNGF is likely ascribed to the following reasons: 1) the small size effect of Cu clusters can decrease the coordination number and regulate the electrophilicity of Cu.…”

Recent Advances in Metal‐Organic Framework Derivatives as Oxygen Catalysts for Zinc‐Air Batteries

“…Consequently, the single‐atom Fe, Mn−N−C catalyst demonstrated better ORR performance than Fe−N−C and Mn−N−C, which even outperformed Pt/C catalyst when used as an air electrode in a primary Zn‐air battery. Lai et al proposed a post‐coordination strategy for anchoring single‐atom Cu on a N‐doped carbon derived from the ZIF‐8 precursor (Figure b) …”

“… a) Illustration of synthetic procedures for hollow Fe, Mn−N/C with single‐atom Fe and Mn from a ZIF‐8 precursor; b) Illustration of synthetic strategy of Cu−N−C composite with single‐atom Cu, c) electron transfer number (n) for ORR of Cu−N−C catalyst in 0.1 M KOH; d) Illustration of the preparation procedure for Mn/C−NO, e) Fourier transformed Mn K‐edge XANES spectra for Mn foil, MnO/C, and Mn/C−NO, (f) Optimized Mn‐N3O1 structure with ORR intermediates of O*, HO* and HOO*. Reprinted with permission from (a) Copyright 2018 Royal Society of Chemistry, (b), (c) Copyright 2018 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim, (d)–(f) Copyright 2018 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim.…”

A New Generation of Platinum‐Copper Electrocatalysts with Ultra‐Low Concentrations of Platinum for Oxygen‐Reduction Reactions in Alkaline Media

“…Table S2 compares the catalytic activity of Pt 0.25 Cu electrocatalyst with the published in the literature. It is noteworthy that our Pt−Cu NPs exhibit excellent activity on the bleeding edge, compared to most of the reported electrocatalysts . The high catalytic activity of Pt 0.25 Cu electrocatalyst may be due to optimum metal loading, the small size of NPs, twinned effects, and the excellent electron interaction .…”

“…In this study, Pt−Cu NPs are rich in Cu, leading to enhanced catalytic activity. The alloying Pt with 3d transition metals can change the electronic structure of Pt, thus prompting the O 2 reduction . The presence of Cu may enhance the OH ˗ generation, and thus improving CO tolerance .…”