Enabling Direct H2O2 Production in Acidic Media through Rational Design of Transition Metal Single Atom Catalyst

Abstract

The electrochemical oxygen reduction reaction in acidic media offers an attractive route for direct hydrogen peroxide (H 2 O 2 ) generation and on-site applications. Unfortunately there is still a lack of cost-effective electrocatalysts with high catalytic performance. Here, we theoretically designed and experimentally demonstrated that a cobalt single-atom catalyst (Co SAC) anchored in nitrogendoped graphene, with optimized adsorption energy of the *OOH intermediate, exhibited a high H 2 O 2 production rate, which even slightly outperformed the state-of-the-art noble-metal-based electrocatalysts. The kinetic current of H 2 O 2 production over Co SAC could reach 1 mA=cm 2 disk at 0.6 V versus reversible hydrogen electrode in 0.1 M HClO 4 with H 2 O 2 faraday efficiency > 90%, and these performance measures could be sustained for 10 h without decay. Further kinetic analysis and operando X-ray absorption study combined with density functional theory (DFT) calculation demonstrated that the nitrogen-coordinated single Co atom was the active site and the reaction was rate-limited by the first electron transfer step.

Designing the future atomic electrocatalyst for efficient energy systems

“…Gao et al found that the Co SAC has the optimum close to zero ΔG OOH* among Mn, Fe, Co, Ni, and Cu, suggesting it has the highest catalytic activity toward the two-electron ORR pathway ( Figure 5C). 31 The subsequent electrochemical tests were consistent with the theoretical prediction, showing that the Co-NC SAC even slightly outperformed the best previously reported catalysts in acidic media, the Pd-Hg alloy. 114 Jiang et al conducted a study on the two-electron ORR SACs with CNTs as the support.…”

“…For instance, the two-electron pathway ORR is more favorable on SACs since the adsorption of O 2 preferably takes the end-on configuration, which favors the formation of OOH* instead of O-O bond cleavage. 31 The strong metal-support interaction not only stabilizes the isolated atoms and prevents the agglomerations, but also substantially modulates the atom electronic state via charge-transfer. This is frequently discussed and demonstrated via characterization techniques and density funcitonal theory (DFT) calculations.…”

Catalyst Design for Electrochemical Oxygen Reduction toward Hydrogen Peroxide

“…More recently, Liu and co-workers carried out a detailed kinetic analysis on Co-NC single atom catalyst for 2e − ORR in acidic media. [98] By tuning electrolyte pH and O 2 partial pressure, they observed a H + reaction order of −0.05-−0.07 and a O 2 reaction order of 0.53-0.9 within an overpotential of 0 to 250 mV, suggesting the first electron transfer step (O 2 + * + e − → *O 2 − ) to be the rate-limiting step for H 2 O 2 synthesis at this onset region (Figure 5c).…”

“…Reproduced with permission. [98] Copyright 2020, Elsevier. d) Atomic distribution and coordination environmental analysis of Fe−CNT catalyst by atom probe topography, together with the determined H 2 O 2 selectivity on different motifs.…”

Atomic engineering of single-atom nanozymes for enzyme-like catalysis

“…97 Thirdly, the enzyme-like catalysis on SAzymes in essence is the heterocatalysis process, the selectivity arises from the differences of interaction force between single-sites and reactants, which includes the adsorption, desorption, and electron and proton transfer processes. Based on the well-established singleatom electrocatalyst and electrochemical research systems, the reaction kinetics and electrocatalytic properties of SACs could be extended to the analogous enzyme-like catalysis to ltrate highly selective SAzymes, 98 for instance, the SACs with highly selectivity in four-electron or two-electron oxygen reduction reaction electrocatalysis respectively corresponding to the halfreaction of oxidase-like or glucose oxidase-like SAzyme catalysis. 99,100 Shen et al reported the catalyst of single-atom Pt with a CuS x support (h-Pt 1 -CuS x ), which can consistently reduce O 2 to H 2 O 2 with high selectivity.…”