γ-In2S3 nanosheets-composed flowerlike nanostructure doped by Al3+ ions with optimal electronic structure and decreased work function of γ-In2S3 for CO2 electroreduction to formate

It is an urgent imperative to convert CO2 molecules into valuable chemicals or fuels for mitigating the greenhouse effect and energy dilemma. Herein, γ-In2S3 nanosheets-composed flowerlike nanostructure doped by tunable amount of Al3+ ions was fabricated by a one-step solution-phase avenue for efficient CO2ER to formate. The particular nanosheets-composed flowerlike nanostructure exhibited good gas-permeable behavior, enlarging the capacity of CO2 adsorption and accelerating the mass-transport efficiency. The Al dopant in γ-In2S3 optimized the electronic structure of γ-In2S3, which enhanced the carrier density, conductivity, and exposed active sites. Besides, Al doping reduced the work function of γ-In2S3, which brought about the fast Faradaic process of CO2 activation and speeded up the subsequent reduction reaction. The optimal Al4.8%-In2S3 displayed the maximal formate Faradaic efficiency (FEHCOO–) of 91.2% at −1.0 V and maintained with a high FEHCOO–> 80% in a potential range of −0.9 to −1.2 V. Moreover, it exhibited a high formate energy efficiency (EEHCOO–) of 58.5% at −1.0 V and kept with a high EEHCOO–> 50% in a potential range of −0.9 to −1.2 V. Besides, Al4.8%-In2S3 delivered the partial current density of 23 mA cm−2 at −1.0 V for formate and increased to 31.7 mA cm−2 at −1.2 V. It also maintained over 90.8% of FEHCOO– and the current value decayed less than 2% after 14 h continuous electrocatalysis at −1.0 V, exhibiting remarkable operational stability in CO2ER. This work optimized electronic structure of metal chalcogenides by heterocations doping toward highly active and selective CO2ER to formate and beyond.