Addressing the critical scientific challenge of enhancing the catalytic efficiency of transition metal-based metal–organic framework (MOF) materials in the two-electron oxygen reduction reaction (2e– ORR) for the electrochemical synthesis of H2O2 is of paramount importance in a related field. In this context, we had developed an interface synthetic strategy for constructing a series of bimetallic Ni–M (M = Co, Fe, Cu) center MOFs. This approach capitalized on the strong synergy among metallic ions, effectively regulating the electronic structure and thereby improving the catalytic activity of Ni active sites. Notably, the proposed Ni–Co MOF catalyst demonstrated exceptional 2e– ORR activity, achieving a remarkable H2O2 selectivity of up to 96%. This performance significantly surpassed that of Ni–Fe (54%) and Ni–Cu (67%) MOFs, as well as many other reported transition metal catalysts. Detailed studies on the structure–function relationship at the atomic level unveiled that Ni species in a high oxidation state, effectively regulated and stabilized by adjacent Co2+ ions, played a pivotal role in ensuring the superior 2e– ORR activity of the Ni–Co MOF. These physical-chemical insights into the reaction mechanism and structure–function relationships offer valuable guidance for the rational design of highly efficient MOF-based catalysts and reaction systems for on-site electrochemical synthesis of H2O2 via a 2e– ORR process.
A great deal of research has been carried out on the design of Pd-based catalysts in the direct synthesis of H2O2, mainly for the purpose of improving the H2O2 selectivity by weakening the activation energy on the Pd active site and thus inhibiting the dissociation of the O–O bonds in O2*, OOH*, and HOOH*. However, this often results in insufficient activation energy for the reaction between H2 and O2 on Pd, leading to difficulties in improving both the selectivity and productivity of H2O2 simultaneously. Based on this, this study reports an efficient catalyst composed of amine-functionalized SBA-15-supported Pd. The strong metal–support interaction not only makes the PdNPs highly dispersed with more Pd active sites but also improves the stability of the catalyst. The amine group modification increases the proportion of Pd0, further enhancing Pd activity and promoting the adsorption and conversion of H2 and O2 on Pd, thereby significantly increasing H2O2 productivity. Additionally, the density-functional theory simulation results showed that due to the hydrogen-bonding force between the amine group and H2O2, this particular anchoring effect would make the hydrogenation and decomposition of H2O2 effectively suppressed. Ultimately, both the selectivity and productivity of H2O2 are improved simultaneously.
Electrochemical two-electron oxygen reduction reaction (2e − ORR) serves as an appealing approach for green hydrogen peroxide (H 2 O 2 ) production. However, the corresponding progress in efficient non-precious metal catalysts for acidic 2e − ORR has not kept pace, with the research model being almost confined to Co-based system. Here, guided by molecular dynamics simulations, the active nature and origin of pyrolyzed Cr−N 4 catalysts for ORR are unveiled, wherein the over-strong oxygen affinity of the Cr center is counterbalanced by a spontaneous axial O-coordination. By creating an oxidation-induced electron-deficient environment, the Cr−N 4 can be flexibly tailored for selective H 2 O 2 formation. A single-atom Cr−N 4 /C(O) catalyst is developed experimentally, which rivals and even slightly outperforms its Co-based counterpart in terms of selectivity (92% versus 71%) and productivity (202 versus 145 mmol g cat −1 h −1 ) for H 2 O 2 . More encouragingly, the Cr-based catalysts exhibit minimal reactivity towards H 2 O 2 -related side reactions, with the metal component being robust against leaching. This research marks the first identification of pyrolyzed Cr−N 4 catalysts as competent for acidic two-electron O 2 reduction to H 2 O 2 . The innovative models and insights offer profound guidance for the design of future-generation catalysts for electrochemical H 2 O 2 synthesis.
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