化学吸附Chemisorption

吸附热一般为 40–800 kJ/mol，接近化学反应热；只在特定吸附质与吸附剂之间发生（如 H₂ 在 Ni、Pt 上，CO 在 Pt 上，O₂ 在多数金属上）；吸附分子可能解离（H₂ → 2 H*，N₂ → 2 N*），化学键被削弱或改变；高温下脱附时可能生成与原吸附质不同的物质。由于需要克服活化能，化学吸附速率随温度升高而加快。

Heats of adsorption are typically 40–800 kJ/mol, close to reaction enthalpies; it occurs only for particular pairs, such as H₂ on Ni or Pt, CO on Pt and O₂ on most metals; the adsorbate may dissociate (H₂ → 2 H*, N₂ → 2 N*) with its bonds weakened or changed; and desorption at high temperature may release a different substance. Because activation energy must often be overcome, the rate rises with temperature.

多相催化的核心是反应物在催化剂表面的化学吸附：吸附太弱，反应物不能被活化；吸附太强，产物难以脱附而毒化表面。萨巴蒂埃原理指出最佳催化剂的吸附强度适中，由此得到“火山形曲线”。埃特尔用超高真空表面科学方法研究了 H₂ 在 Pt 上、N₂ 在 Fe 上的化学吸附，阐明了合成氨机理，获 2007 年诺贝尔化学奖。

The heart of heterogeneous catalysis is chemisorption of reactants on the catalyst: too weak and the reactants are not activated, too strong and the products cannot desorb and poison the surface. Sabatier's principle says the best catalysts bind with intermediate strength, giving the 'volcano plot'. Ertl used ultra-high-vacuum surface science to study H₂ on Pt and N₂ on Fe, explaining the mechanism of ammonia synthesis, and received the 2007 Nobel Prize in Chemistry.

程序升温脱附（TPD）、程序升温还原（TPR）和脉冲化学吸附用于测定催化剂活性位数目和金属分散度；红外光谱和 X 射线光电子能谱可以表征吸附态。化学吸附还用于气体传感器（SnO₂ 对还原性气体）、腐蚀与钝化研究和自组装单分子膜（硫醇在金表面）。

Temperature-programmed desorption (TPD), temperature-programmed reduction (TPR) and pulse chemisorption count active sites and measure metal dispersion; infrared spectroscopy and X-ray photoelectron spectroscopy characterise adsorbed states. Chemisorption also underlies gas sensors (SnO₂ for reducing gases), studies of corrosion and passivation, and self-assembled monolayers such as thiols on gold.