Preparation of hydrophobic three-dimensional hierarchical porous zinc oxide for the promotion of electrochemical CO2 reduction

The construction of three-dimensional hierarchical porous and hydrophobic-aerophilic interfaces facilitates mass transport and CO 2 enrichment by kinetically accelerating the CO 2 electrochemical reduction reaction (CO 2 RR). Inspired by the process of baking bread, in which pores that connect the interior of the bread to its exterior are created, we propose a template-free metal carbonate-porous metal oxide (MC-PMO) strategy to synthesize porous metal oxides with tunable pore size. Using this strategy, a series of porous metal oxides with different morphologies and different metals was successfully developed. Furthermore, the effect of catalyst mass transport on the CO 2 RR was explored. The porous catalysts with suitable pore size promoted mass transfer, which significantly enhanced the activation and transformation of CO 2 . In addition, based on a hydrophobic group-modified metal oxide surface (HG-MO) strategy, a hydrophobic-aerophilic interface microenvironment was constructed to reduce the water dissociation activity and effectively inhibit the hydrogen evolution reaction (HER). HP-ZnO-500 @ 2-NTL was obtained by modifying hierarchical porous zinc oxide (HP-ZnO-500) with the hydrophobic 2-naphthalenethiol (2-NTL). The hydrophobic surface of HP-ZnO-500 @ 2-NTL was easily enriched with CO 2 gas under the influence of the “plastron effect”, and the surface hydrophobic film stabilized the M–H bond. Thus, HER was suppressed. At − 1.0 V vs. RHE, HP-ZnO-500 @ 2-NTL achieved a faradaic efficiency of CO (FE CO ) as high as 83.0%, and displayed high catalytic activity in a wide potential range. The “MC-PMO” strategy and “HG-MO” strategy reported herein are universal and are expected to guide the further preparation and modification of different metal-based porous metal oxides for sustainable CO 2 RR.