Engineering of Lewis acid–base interfaces in Cu₂S/ZnIn₂S₄ hollow hetero-nanocages for enhanced photocatalytic CO₂ reduction

Selective photocatalytic CO₂ reduction (PCR) to CH₄ remains challenging due to the sluggish charge transfer kinetics and the involved complicated C₁ intermediates. Herein, deliberate engineering of Lewis acid-base interfaces in Cu₂S/ZnIn₂S₄ hollow hetero-nanocages (HHNCs) was carried out, and enhanced PCR activity and selectivity were achieved due to accelerated electron transfer and stabilized intermediates. Both experimental and theoretical results have demonstrated the construction of a Lewis base interface with Cu₂S and a Lewis acid interface with ZnIn₂S₄, which exhibited strong CO₂ adsorption and reduction of the Gibbs free energy in the hydrogenation step (*CO to *CHO). As a consequence, a CH₄ yield of 23.3 μmol g^-1 h^-1 under visible light irradiation (<i>λ</i> > 400 nm) was obtained with the Cu₂S/ZnIn₂S₄ HHNCs, approximately 13.7, 10.1 and 6.3 times higher than those of bare Cu₂S, ZnIn₂S₄ and a physically mixed sample (Cu₂S/ZnIn₂S₄-mix), respectively. The product selectivity of CH₄ was as high as 93.2%, in sharp contrast with 59.5% for the Cu₂S/ZnIn₂S₄-mix, 53.1% for Cu₂S and 35.4% for ZnIn₂S₄. This work demonstrates a rational strategy to engineer heterogenous Lewis acid-base interfaces for improving PCR activity and selectivity.