Stabilizing indium sulfide for CO2 electroreduction to formate at high rate by zinc incorporation

Recently developed solid-state catalysts can mediate carbon dioxide (CO2) electroreduction to valuable products at high rates and selectivities. However, under commercially relevant current densities of > 200 milliamperes per square centimeter (mA cm(-2)), catalysts often undergo particle agglomeration, active-phase change, and/or element dissolution, making the long-term operational stability a considerable challenge. Here we report an indium sulfide catalyst that is stabilized by adding zinc in the structure and shows dramatically improved stability. The obtained ZnIn2S4 catalyst can reduce CO2 to formate with 99.3% Faradaic efficiency at 300 mA cm(-2) over 60 h of continuous operation without decay. By contrast, similarly synthesized indium sulfide without zinc participation deteriorates quickly under the same conditions. Combining experimental and theoretical studies, we unveil that the introduction of zinc largely enhances the covalency of In-S bonds, which locks sulfur-a catalytic site that can activate H2O to react with CO2, yielding HCOO* intermediates-from being dissolved during high-rate electrolysis. Developing durable catalysts for carbon dioxide reduction to formate at commercial-scale current densities is challenging. This work reports that indium sulfide stabilized through zinc incorporation can produce formate efficiently and quickly at high current densities over long timescales.

Automated summary

Recently developed solid-state catalysts can efficiently mediate the electroreduction of carbon dioxide to formate at high current densities. The introduction of zinc into indium sulfide can greatly enhance the stability and covalency of the catalyst, preventing the dissolution of active sites during high-rate electrolysis.