Proton-coupled electron transfer (PCET) is important in many areas of chemistry, biology, and materials science, and has been reviewed extensively over the past decades. PCET is conceptualised in socalled square schemes, see Figure , where the horizontal axes refer to the isolated proton transfer event and the vertical axes describe the isolated electron transfer event. These axes are connected to experimentally accessible descriptors, the pK a value and the redox potential, making it clear it is an energybased scheme. A chemically intuitive explanation for PCET being preferable over sequential steps is that it prevents charge build-up in the 'avoided' chargeseparated intermediates depicted in the off-diagonal corners of the square scheme.