Customizing Ferrocene Units into Atomically Precise Cu11 Clusters for Boosting Oxygen Reduction to H2O2.

Precisely integrating an organometallic compound into atomically defined copper clusters holds great promise for boosting catalytic performance and uncovering detailed structure-activity relationships. Herein, we report the first successful synthesis of atomically precise copper clusters (Cu11-DPPF, DPPF = 1,1-bis(diphenylphosphino)ferrocene) carrying ferrocene units using DPPF and cyclohexanethiol as coligands through a straightforward, scalable, and versatile synthetic strategy, which is also applicable to synthesize its analogous Cu11-DPPM (DPPM = bis(diphenylphosphino)methane) and Cu11-DPPE (DPPE = 1,2-bis(diphenylphosphino)ethane) clusters. All three Cu11 clusters exhibit a similar structural feature like a cloverleaf-like rotational assembly, comprising three fused butterfly-shaped Cu5S7P2 subunits. Among them, Cu11-DPPF exhibits superior catalytic performance in the two-electron oxygen reduction reaction (2e- ORR), achieving H2O2 selectivity exceeding 97.5% within the whole potential range of 0.35 to 0.55 V versus the reversible hydrogen electrode (RHE), fully deserving to be called the optimal 2e- ORR catalyst in the metal cluster community. DFT simulations, in conjunction with multiple characterization techniques such as operando infrared spectroscopy and X-ray absorption fine structure spectroscopy, reveal that the introduction of ferrocene units in Cu11 clusters facilitates favorable electron redistribution, which optimizes the adsorption of OOH* in the rate-determining step, thereby promoting efficient conversion of OOH* to H2O2. The practical efficacy of Cu11-DPPF is further demonstrated in Fenton-like reactions for hydroxyl radical-initiated pollutant degradation via in situ H2O2 generation. This work provides crucial insights into the design of atomically precise ferrocene-functionalized copper cluster hybrid catalysts and deepens our understanding of their structure-activity relationships in 2e- ORR pathways for H2O2 production.