Thiourea-assisted coating of dispersed copper electrocatalysts on Si photocathodes for solar hydrogen production

•We develop a spin-coating and in-situ photoelectrochemical reduction method to prepare dispersed Cu on a photocathode.•We find that thiourea in the precursor plays an important role in obtaining dispersed Cu particles on the Si surface.•The performance of Cu/Si prepared with thiourea in the precursor solution is higher than a sample without thiourea.