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We show here that a physical activation process that is diffusion-controlled yields an activated carbon whose chemistry – both elemental and functional – varies radially through the particles. For the ∼100 μm particles considered here, diffusion-controlled activation in CO2 at 800 °C saw a halving in the oxygen concentration from the particle periphery to its center. It was also observed that this activation process leads to an increase in keto and quinone groups from the particle periphery towards the center and the inverse for other carbonyls as well as ether and hydroxyl groups, suggesting the two are formed under CO2-poor and -rich environments, respectively. In contrast to these observations, use of physical activation processes where diffusion-control is absent are shown to yield carbons whose chemistry is radially invariant. This suggests that a non-diffusion limited activation processes should be used if the performance of a carbon is dependent on having a specific optimal pore surface chemical composition. SS acknowledges the award of Adelaide Scholarships International (ASI) from the University of Adelaide. SHM acknowledges the award of a President's Scholarship from the University of South Australia. CH acknowledges a joint scholarship provided by China Scholarship Council (CSC) and the University of Adelaide. The support of the Australian Research Council Discovery Program (DP110101293) is also gratefully acknowledged.

There are circumstances where it is desirable to achieve a particular, optimal, pore size distribution (PSD) in a carbon, including in the molecular sieving, gas storage, CO2-capture and electrochemical energy storage. Activation protocols that cycle a carbon a number of times between a low-temperature oxygen chemisorption process and a higher temperature pyrolysis process have been proposed as a means of yielding such desired PSDs. However, it is shown here that for PFA-based char particles of ∼100 μm in size, only the super-micropores are substantially developed under such an activation protocol, with the ultra-micropores being substantially un-touched. It is also shown that a typical CO2-activation process yields similar control over PSD development. As this process is nearly 15 times faster than the cyclic-O2 protocol and yields larger pore volumes and areas for a given level of conversion, it is to be preferred unless spatial homogeneous porosity within the particles is also desired. If such homogeneity is desired, it is shown here that CO2 activation should continue to be used but at a rate of around one-tenth the typical; this slow rate also has the advantage of producing pore volumes and areas substantially greater than those obtained using the other activation protocols. CH acknowledges a joint scholarship provided by China Scholarship Council (CSC) and the University of Adelaide. SS acknowledges the award of International Postgraduate Research Scholarship (IPRS) from the University of Adelaide. SHM acknowledges the award of a President’s Scholarship from the University of South Australia. The support of the Australian Research Council Discovery Program (DP110101293) is also gratefully acknowledged.