Table 3. Comparison of Cu_xO-Based Photocathode Performance Synthesized using Different Techniques.

photocathode	thickness (nm)	fabrication technique	photocurrent	refs
NiO–CuO thin film	850	sol–gel spin coating	–1.07 mA/cm2 at –0.55 V (Ag/AgCl)	(24)
CuO thin film	∼500	sputtering	–0.65 mA/cm2 at –0.45 V (Ag/AgCl)	(66)
Li-doped CuO nanoparticles	1700	flame spray pyrolysis	–1.7 mA/cm2 at –0.55 V (Ag/AgCl)	(27)
CuO thin film	500	RF-magnetron sputtering	–3.1 mA/cm2 at 0 V (RHE)	(67)
CuO nanoparticles films	1340	spin coating	–1.2 mA/cm2 at –0.55 V (Ag/AgCl)	(68)
CuO thin film with TiO2 protecting layer and Au–Pd co-catalyst nanostructures (CuO–TiO2–AuPd)	∼500	sol–gel method and RF sputtering	–1.9 mA/cm2 at 0 V vs RHE	(69)
tenorite CuO thin films	∼500	spray pyrolysis	–24 mA/cm2 at 0.25 V vs RHE	(33)
Cu2O/CuO/C	∼2000	electrodeposition	–7.5 mA/cm2 at –0.1 V vs RHE	(70)
CuO	∼700	spin coating	–19.12 mA/cm2 at –1 V vs RHE	present work