Enhanced catalytic activity towards hydrogen evolution on polythiophene via microstructural changes

The discovery of poly(2,2′-bithiophene) (PBTh) as a photo-electrochemical catalyst for the hydrogen evolution reaction (HER) presents a novel electrode material for the transition to a sustainable hydrogen energy economy. Nonetheless, it remains limited by a low hydrogen evolution rate. We here investigate two methods in which to increase the catalytic activity of PBTh: using humidity for alternative templating and substrate roughening. It was found that exposure of the oxidant solution to humidity prior to polymerisation causes the formation of new microstructures that was found to increase catalytic activity of the PBTh film by over four times, from 14 to 57 µA cm-2. It was also found that control of the atmospheric environment proved critical. In contrast, the roughening of the substrate did not consistently lead to an increase in performance and was attributed to poor adhesion and electrical contact of the film to the substrate. During these tests however, a photo-electrocatalytic current of 150 μA cm−2 was recorded in pH 7.0 and an underpotential of 0.12 V on an un-roughened PBTh sample. This represents the highest reported value for PBTh thus far and a significant achievement for its further development towards a low-cost and efficient HER catalyst.