Confinement Strategies for Precise Synthesis of Efficient Electrocatalysts from the Macroscopic to the Atomic Level

ConspectusTremendous efforts have shown that the precise control of the electrocatalyst structure and morphology can boost their catalytic performance toward diverse important reactions such as oxygen reduction/evolution reactions (ORR/OER), hydrogen oxidation/evolution reaction (HOR/HER), carbon dioxide/nitrogen reduction reactions (CO2RR/NRR), etc. The physical and chemical confined syntheses have witnessed the success in manipulating catalyst features from macroscopic to atomic level to deal with various application demands.In this Account, we summarize the recent innovative advances with an emphasis on our solutions in the precise synthesis of efficient electrocatalysts via the confinement strategies at various scales. By categorizing the confinement effects into the precursor self-confinement, nanospace confinement, and chemical binding atomic confinement with representative examples, we systematically introduced the confinement strategies in the synthesis of well-defined structures from the macroscopic to nanoscopic and atomic level. (1) Precursor self-confinement strategy. The electrode with a macroscopic hierarchical micro/nanoarray structure provides a large exposed surface area and structural merits for highly intensive electron transport and mass transfer as well as prompt gas release, which enables high-performance electrocatalytic energy devices. The self-confinement effect from the presynthesized precursors promises to rationally design and precisely fabricate such electrodes at the macroscopic level. (2) Nanospace confinement strategy. Metal clusters and nanoparticles (NPs) offer diverse surface sites for the adsorption, activation, and transformation of reactants/intermediates. The confinement from nanospaces such as 0D nanopores, 1D nanochannels, 2D interlayer spaces, and 3D interconnected nanochannels enables the synthesis of nanoclusters and NPs with controlled morphologies and structures at the nanoscopic level, allowing for investigating the collective activation of intermediates, interaction with support, size-dependent structure–performance relationship. etc. (3) Chemical binding atomic confinement strategy. The chemical binding confinement makes it possible to synthesize single atom catalysts (SACs) with the capability of delicately tailoring their electronic structure and chemical environment at the atomic level, providing opportunities for in-depth understanding the underlying catalytic processes and the structure–performance relationships. (4) Integrated confinement strategy. Taking all these confinement effects into account together is powerful to mitigate the challenges in the synthetic fields such as well-defined high-density SACs. With these insights, this Account proposes the remaining challenges and possible solutions for the precise synthesis of next-generation well-defined electrocatalysts from macroscopic to atomic level by exploring suitable confinement effects and integrating them with other techniques, which may open up opportunities for bridging the gap between the fundamental research and industrial applications.