Identifying Activity Trends for the Electrochemical Production of H₂O₂ on M–N–C Single-Atom Catalysts Using Theoretical Kinetic Computations

Abstract

Metal−nitrogen−carbon (M−N−C) single-atom catalysts (SACs) have shown high potential to generate H 2 O 2 through the two-electron oxygen reduction reaction (2e − ORR) pathway in an acidic electrolyte. However, there is still a lack of effective kinetic computation to reveal M−N−C SACs' intrinsic catalytical performance toward 2e − ORR. Here, we combine the experimental and computational efforts to study the 2e − ORR activity trends of M−N−C SACs (M = Co, Fe, and Mn). The experimental results show that Co−N−C and Mn−N−C SACs favor the 2e − ORR pathway but Fe−N−C SAC favors the 4e − ORR pathway. Using systematic kinetic calculation, we demonstrated that desorption of HOOH* or H 2 O* was a real determining step of the ORR pathway on M−N−C SACs. The difference in the desorption energy between H 2 O* and HOOH* reaction oxygen intermediates (E H 2 O* − E HOOH* ) on a metal active center is a credible descriptor to illustrate and predict the H 2 O 2 selectivity of M−N−C SACs. The predicted high H 2 O 2 selectivity of Ni−N−C SACs from the descriptor is consistent with the experimental results. This study clarifies the mechanism of ORR on M−N−C SACs and identifies the determining factors of the ORR pathway, providing new insights into the rational design of high-H 2 O 2 -selectivity M−N−C SACs.

Recent Advances of Electrocatalyst and Cell Design for Hydrogen Peroxide Production

“…Currently, researchers are devoted to noble metal minimization [69][70][71]. Constructing atomically dispersed catalysts has received extensive attention, which could lower the cost and realize end-on adsorption [72][73][74]. These factors, such as ligand effect, support effect, and impact of metal loading has an evident influence on the ORR activity and selectivity.…”

“…Inspired by this, researchers are dedicated to transitional metal-nitrogen-doped carbon (M-N-C, M = Fe, Co, Mn, Cu, Ni) materials, as a promising alternative to the conventional noble metal-based catalysts (e.g., Pd, Au, or Pt) [112,113]. M-N-C materials exhibit high activity comparable to the noble metal-based catalysts with much lower cost [74,[114][115][116][117]. Normally, their ORR activity and selectivity are affected by the central metal atoms, coordination heteroatoms, and other environmental atoms.…”

Recent progress in electrocatalytic selectivity in heterogeneous electro-Fenton processes

“…The difference in the desorption energy between H 2 O* and HOOH* intermediates on the active center is an important descriptor to predict the H 2 O 2 selectivity of catalysts. 76 Penta-coordinated Co-N-C conguration (O-Co-N 2 C 2 ) with the Co center coordinated by two N atoms, two C atoms, and one O atom was conrmed to slightly increase the charge state of the Co center, which can facilitate the adsorption energy towards *OOH to enable the 2e − ORR. In a neutral solution, the as-synthesized O-Co-N 2 C 2 exhibited a selectivity of over 90% in the potential range from 0.36 to 0.8 V vs. RHE.…”

“…The difference in the desorption energy between H 2 O* and HOOH* intermediates on the active center is an important descriptor to predict the H 2 O 2 selectivity of catalysts. 76…”

Cobalt atoms anchored on nitrogen-doped hollow carbon spheres for efficient electrocatalysis of oxygen reduction to H2O2

“…M-N-C materials can bring down the cost and maximize the utilization efficiency simultaneously. Based on the computer technologies and experimental methods, it was shown that Co-N-C follows a 2e − ORR pathway to H 2 O 2 with a proper adsorption energy of * OOH [35][36][37][38]. Therefore, carbon materials can be used in acidic media for H 2 O 2 electrosynthesis via structure geometric regulation, heteroatom doping, and transition metal introduction.…”