The experiments demonstrate that for reduced PFBT Pdots act as a catalyst, there needs to be a stronger proton donor than water in the system. The catalytic behaviour is also static in potential over the range of pH values that were tested and does not follow the reversible hydrogen electrode (RHE) (Figure ). This behaviour indicates that the electrocatalysis relies on an initial reduction of the Pdots instead of a metal-based reaction, for example, a mechanism based on Pd metallic catalyst. The role of the BT unit, therefore, needs to be considered because it will be easier to protonate upon reduction in acidic conditions com-Figure : CVs demonstrating the pH dependence of electrocatalytic hydrogen evolution from PFBT Pdots, in 50 mM phosphate buffer and 50 mM KCl as the supporting electrolyte. Showing the decreasing catalytic current at 50 mVs -1 from pH 4 to pH 7 with a collapse of current between pH 7 and pH 8. pared to basic conditions. If the protonation of BT is faster than the electron transfer to residual Pd from reduced PFBT, the protonation of BT is therefore a possible intermediate involved in the photocatalytic reaction. To compare how Pd-centered catalysis looks in the system a Pd working electrode with the same area as the GC electrode (⊘ 3 mm), the Pd-based mechanism does radically differ from what is seen with the GC electrode (Figure ).