The difference between photocatalysis and photoelectrocatalysis

Photocatalysis and photoelectrocatalysis are two core technological routes that use solar energy to drive chemical transformations. Although both are physically based on semiconductor photoexcitation, they differ significantly in carrier‑dynamics control, reactor architecture, and performance metrics. For researchers and engineers with a new‑energy background, understanding these differences is key to bridging materials development and engineered system integration.

Photocatalysis (Photocatalysis) typically involves semiconductor particles used as catalysts suspended in or supported within the reaction medium. The basic principle is that the semiconductor absorbs photon energy to generate photogenerated electron–hole pairs, which directly drive redox reactions at active sites on the surface of individual particles. This process entirely relies on built‑in fields or potential differences between crystal facets within the material to drive charge separation. Because carrier migration paths are extremely short at the micro‑/nanoscale, electrons and holes readily undergo nonradiative recombination, which is the primary bottleneck limiting photocatalytic efficiency. In experiments, a stable irradiation environment is essential to ensure scientifically comparable measurements of intrinsic material activity. Using a solar simulator can provide spectral match, irradiance uniformity, and temporal stability that meet the international AAA standard AM 1.5G reference spectrum, offering a reproducible physical basis for photocatalytic water splitting for H₂ production or CO₂ reduction experiments.

Photoelectrocatalysis (Photoelectrocatalysis, PEC) introduces an external electric field in addition to illumination. By fabricating the semiconductor into a photoelectrode and placing it in an electrochemical testing setup, an externally applied bias is used as an additional driving force to force photogenerated carriers to migrate in opposite directions. The presence of an external bias effectively widens the space‑charge region (depletion layer), substantially suppresses charge recombination, and can be used to lower the overpotential required for specific reactions by tuning the applied potential. In performance evaluation, PEC focuses not only on gas‑phase product formation rates but also on current density, incident photon‑to‑current conversion efficiency (IPCE), and Faradaic efficiency. The PEC2000 EASY photoelectrochemical testing system is an integrated solution designed for such studies. The system combines a high‑uniformity light source with a high‑gas‑tight electrochemical cell, enabling precise acquisition of the dynamic photocurrent–potential response and helping researchers decouple light absorption, charge separation, and interfacial catalytic kinetics contributions to overall energy conversion efficiency.

In summary, photocatalysis places greater emphasis on band‑structure engineering and microstructural control of the material itself, with relatively simple reactor designs suitable for large‑scale, low‑cost deployment; photoelectrocatalysis, by contrast, leverages photoelectric synergy to achieve precise control over reaction pathways and a higher ceiling for energy conversion, offering stronger engineering certainty. By combining high‑precision simulated light fields with specialized testing terminals, researchers can comprehensively reveal the transport‑kinetic mechanisms of photogenerated carriers and advance the industrialization of hydrogen and carbon‑neutral technologies.