The selectivity of photocatalytic CO₂ reduction to CH₄ can be enhanced over Pt-decorated semiconductors, which is commonly attributed to the fact that a Schottky junction is formed, thus enhancing photoinduced electron lifetime. However, it is difficult to understand why the yield of CO—the other product of photocatalytic CO₂ reduction—is decreased only in terms of photoinduced electron lifetime. In this work, the mechanism of Pt-promoted CH₄ formation was probed again in a gas-solid system of photocatalytic CO₂ reduction over highly-dispersed-Pt decorated In₂O₃ nanorods (Pt/In₂O₃). It was found that the presence of Pt modulates the surface property of In₂O₃ due to electronic and steric effect, resulting in a loss of HCO₃⁻, b-CO₃²⁻ and m-CO₃²⁻ species for the coadsorption of CO₂ with H₂O. However, this is not directly related with the high CH₄ selectivity and low CO yield on the Pt/In₂O₃ photocatalysts. Photocatalytic reductions of CO, HCOOH, CH₂O, and CH₃OH as well as photocatalytic CO₂ reduction over photocatalysts with different H₂ uptakes confirm that H adatoms derived from H₂ or H₂O dissociation on Pt play a key role in the formation of CH₄. Low H₂ dissociation barrier on Pt and weak HPt bond facilitate the bonding of C in CO₂ with H, thus restraining CO production. In other words, the metallic Pt acts as atomic hydrogen reservoir that supplies sufficient and readily available protons for CH₄ formation over Pt-decorated semiconductors. The present work offers a new window to explore non-noble metals or their alloys with stability in air and high dissociation ability to H₂ or H₂O as a replacement of Pt for CO₂ photoreduction to CH₄.

相较于用Pt装饰的半导体，可以提高光催化还原CO ₂对CH ₄的选择性，这通常归因于形成肖特基结的事实，从而提高了光致电子寿命。但是，很难理解为什么仅光诱导的电子寿命就降低了CO的收率（光催化还原CO ₂的另一种产物）。在这项工作中，在高分散的Pt装饰的In ₂ O ₃纳米棒（Pt / In ₂ O _3）上的光催化CO ₂还原的气固系统中，再次探讨了Pt促进CH ₄形成的机理。）。我们发现，Pt的存在下调节在表面属性₂ ö ₃由于电子和空间位阻效应，导致HCO损失₃ ^-，B-CO ₃ ^2-和M-CO ₃ ^2-物种的共吸附CO ₂与H ₂ O混合。然而，这与Pt / In ₂ O ₃光催化剂上的高CH ₄选择性和低CO收率没有直接关系。与具有不同H的光催化剂相比，CO，HCOOH，CH ₂ O和CH ₃ OH的光催化还原以及CO _2的光催化还原_2次吸收证实，源自H ₂或H ₂ O在Pt上解离的H原子在CH ₄的形成中起关键作用。Pt上的低H ₂解离势垒和弱H Pt键促进了CO _2中的C与H的键合，从而抑制了CO的产生。换句话说，金属Pt充当原子氢储库，可为装饰Pt的半导体上的CH ₄形成提供足够且容易获得的质子。本工作为探索在空气中具有稳定性且对H ₂或H ₂ O具有高离解能力以取代Pt替代CO _2的非贵金属或其合金提供了新的窗口。光还原为CH ₄。