= Solution
The initial <nitrogen> environment loses intensity on heating, and a lower-binding-energy component becomes prominent near the highest temperatures. \b[A change of surface chemical species accompanies loss or conversion of the original <adsorbate>.] Plausible processes include thermally activated decomposition with nitrogen-containing fragments remaining on <copper>, <desorption> of intact material or fragments, and rearrangement of the coordination environment. The extra components at intermediate temperatures suggest coexistence rather than a rigid, uniform shift of every molecule.
The individual curves have vertical offsets, so their baseline height is not a coverage measurement. Integrated, sensitivity-corrected N and C peak areas, a clean heated substrate control, and evolved-gas <mass spectrometry> would help distinguish loss of material from chemical conversion. <binding energy> alone cannot establish a unique fragment structure: local charge, metallic screening and coordination all affect it.
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