Hydrogenation of CO₂ to Methanol on a Au^δ+–In₂O_3–<i>x</i> Catalyst

Abstract

CO&lt;sub&gt;2&lt;/sub&gt; hydrogenation to methanol has attracted increasing attention with the development of renewable hydrogen. A big challenge is to identify catalysts able to achieve high conversion and selectivity. In this work, we report an In&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt;-supported Au catalyst that exhibits excellent performance for hydrogenation of CO&lt;sub&gt;2&lt;/sub&gt; selectively to methanol. &lt;i&gt;In situ&lt;/i&gt; characterizations using time-resolved X-ray diffraction, ambient-pressure X-ray photoelectron spectroscopy, and X-ray absorption spectroscopy confirm that a strong metal–support interaction leads to a reactive Au&lt;sup&gt;δ+&lt;/sup&gt;–In&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3–&lt;i&gt;x&lt;/i&gt;&lt;/sub&gt; interface for activation and hydrogenation of CO&lt;sub&gt;2&lt;/sub&gt; to methanol. An effective gold-indium oxide bonding favors the dispersion of the noble metal and prevents its sintering under reaction conditions. The methanol selectivity reaches 100% at temperatures below 225 °C and is more than 70% at 275 °C over the Au&lt;sup&gt;δ+&lt;/sup&gt;–In&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3–&lt;i&gt;x&lt;/i&gt;&lt;/sub&gt; catalyst. It is even 67.8% with a space time yield of methanol of 0.47 g&lt;sub&gt;MeOH&lt;/sub&gt;/(h·g&lt;sub&gt;cat&lt;/sub&gt;) at 300 °C, 5 MPa, and 21,000 cm&lt;sup&gt;3&lt;/sup&gt; h&lt;sup&gt;–1&lt;/sup&gt; g&lt;sub&gt;cat&lt;/sub&gt;&lt;sup&gt;–1&lt;/sup&gt;. The results obtained here represent the highest selectivity and activity ever reported for CO&lt;sub&gt;2&lt;/sub&gt; hydrogenation over supported gold catalysts. Our study shows that the strong Au/In&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; interaction and the intrinsic chemical activity of In&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; can be used to significantly improve the catalytic performance of Au catalysts, providing promising routes for the rational design and application of Au catalysts beyond CO&lt;sub&gt;2&lt;/sub&gt; hydrogenation.