https://doi.org/10.1351/goldbook.14033
Maximum amount of substance photoadsorbed per area on the uniformly irradiated surface of an adsorbent.
Notes:
- Photoadsorption area number should be preferred to photoadsorption capacity (the original name given to this term), since the latter term is reserved for the fractional number, referring to the number of regular sites available for photoadsorption.
- Mathematical expression, \(\gamma^{\rm{s}} = N_{\rm{max}}/S\), where \(N_{\rm{max}}\) is the maximal number of entities or moles photoadsorbed and \(S\) the total surface area. Experimental values of \(\gamma^{\rm{s}}\) in entities are in the range \(\pu{E10 - E12 cm-2}\).
- The quantity \(N_{\rm{max}}\) can be obtained by approximation from photoadsorption kinetics \(N(t)\) on a uniformly irradiated surface provided that
(i) the powdered sample is uniformly irradiated. Then, the area of the irradiated surface is \(S = m a^{\rm{s}}\), where \(m\) is the mass of the sample and \(a^{\rm{s}}\) is the specific surface area (\(\pu{m2 kg-1}\)) of a given adsorbent, or
(ii) the efficiency of desorption of the adsorbed species (via a physical process) is negligible. Then the number of photocatalytic centres can be estimated from the photoadsorption area number, \(\gamma^{\rm{s}}\), to determine TON and TOF for a given photocatalytic reaction.
See also: photoadsorption capacity, photoadsorption fraction