Tuning the Coordination Environment in Single-Atom Catalysts to Achieve Highly Efficient Oxygen Reduction Reactions

Abstract

Designing atomically dispersed metal catalysts for oxygen reduction reaction (ORR) is a promising approach to achieve efficient energy conversion. Herein, we develop a template-assisted method to synthesize a series of single metal atoms anchored on porous N,S-codoped carbon (NSC) matrix as highly efficient ORR catalysts to investigate the correlation between the structure and their catalytic performance. The structure analysis indicates that an identical synthesis method results in distinguished structural differences between Fe-centered single-atom catalyst (Fe-SAs/NSC) and Co-centered/Ni-centered single-atom catalysts (Co-SAs/NSC and Ni-SAs/NSC) because of the different trends of each metal ion in forming a complex with the N,S-containing precursor during the initial synthesis process. The Fe-SAs/NSC mainly consists of a well-dispersed FeN 4 S 2 center site where S atoms form bonds with the N atoms. The S atoms in Co-SAs/NSC and Ni-SAs/NSC, on the other hand, form metal−S bonds, resulting in CoN 3 S 1 and NiN 3 S 1 center sites. Density functional theory (DFT) reveals that the FeN 4 S 2 center site is more active than the CoN 3 S 1 and NiN 3 S 1 sites, due to the higher charge density, lower energy barriers of the intermediates, and products involved. The experimental results indicate that all three single-atom catalysts could contribute high ORR electrochemical performances, while Fe-SAs/NSC exhibits the highest of all, which is even better than commercial Pt/C. Furthermore, Fe-SAs/NSC also displays high methanol tolerance as compared to commercial Pt/C and high stability up to 5000 cycles. This work provides insights into the rational design of the definitive structure of single-atom catalysts with tunable electrocatalytic activities for efficient energy conversion.

Coordination engineering of iridium nanocluster bifunctional electrocatalyst for highly efficient and pH-universal overall water splitting

“…Figure 3b shows typical current profiles for methanol oxidation reaction in neutral-pH media. These curves reflect that the methanol oxidation onset potentials are 1.03 and 1.37 V (vs. RHE) for Ir-NSG and Ir/C, respectively, indicating a higher adsorption energy of OH* on Ir-NSG, which could be derived from a larger intermolecular hardness factor of the bond between Ir shell site and OH induced by the lower electronegativity of S ligand 35,44 . The higher OH* binding energy is supposed to correlate with binding energies of other oxygen intermediates (e.g., O* and OOH*) and hence OER activities.…”

Co2+‐coordinated NH2‐carbon Quantum Dots Hybrid Precursor for the Rational Synthesis of Co−CoOX/Co−N−C ORR Catalyst

“…For the sake of evaluating the practical application of our catalyst, the durability and methanol‐tolerance are key parameters . As is known to all, 20 % Pt/C catalyst is easily poisoned by methanol . As a comparison, the methanol‐tolerance of the Co−CoO X /Co−N−C and Pt/C catalysts were noted at −0.3 V vs. SCE.…”

Recent Advances in Phosphorus‐Coordinated Transition Metal Single‐Atom Catalysts for Oxygen Reduction Reaction

“…No general rule has been found to control the relative position of metal atom and heteroatoms at the active site. It has been reported that different kinds of metal ions have different tendencies when interacting with heteroatoms in precursors [59] . For example, Co 2+ and Ni 2+ can coordinate with N and S elements at the same time, while Fe 3+ only interacts with N, resulting in products of FeN 4 S 2 , CoN 3 S 1 and NiN 3 S 1 , respectively.…”