Improved solar-driven cathodic protection performance of polymer semiconductor photoelectrodes based on one-dimensional and two-dimensional side chain engineering

Polymer semiconductors with 1D and 2D side chains are prepared for photo-induced cathodic protection (PICP) of metals. Under multiple cycles of light irradiation, the 1D&2D-Side-Chain Polymer (1D&2D-SCPoly) exhibited stable PICP, generating the most negative photoinduced potential and highest cathodic protection current. It released more charge in the dark state for PICP. The performance of 1D&2D-SCPoly photoelectrode in 3.5 % NaCl solution remained superior to that of 1D-SCPoly and 2D-SCPoly exposed to a hole scavenger solution. Only the HOMO level of 1D&2D-SCPoly photoelectrode was more positive than the equilibrium potential of oxygen evolution reaction (OER), allowing for the consumption of holes via OER. The 2D side chains increased the surface roughness, featuring numerous rod-like protrusions that enhanced light absorption and created more active sites. This also induced quantum confinement effects conducive to directional electron conduction and electron-hole separation. The 2D side chains enhanced the intrachain conjugation and electron delocalization. The small π-π stacking spacing and rough surface of 1D&2D-SCPoly endow it with strong charge storage and dark-state release capabilities. The 1D&2D-SCPoly balanced intrachain and interchain electron transport and possessed a smaller bandgap, exciton binding energy and work function which improved light utilization efficiency, the probability of electron-hole separation and PICP efficiency.