An effective integrated CuO photocathode to boost photoelectrocatalytic CO conversion

The exploitation of high-performance photocathodes remains a key challenge to bring the feasibility of narrow bandgap semiconductors into fruition for efficient artificial photosynthesis. Herein, we show a highly efficient photocathode system consisting of a photonic crystal structure based on a cuprous oxide (Cu 2 O) semiconductor for good light harvesting, hole-transport layers (HTL: FeOOH) that mediate and stipulate interfacial charge transfer derection from Cu 2 O to FTO, and a polypyrrole (PPy) layer as a sequential multi-electron transfer agent for CO 2 reduction. The integrated Cu 2 O photocathode exhibits a record CO yield of up to 46.17 μmol h −1 at −2.0 V vs. Ag/Ag + , which achieves a high half-cell solar to CO efficiency ( η STC ) of 1.58% and delivers an optimal quantum efficiency of 3.08%, transcending most of the previous Cu 2 O based photocathodes. Moreover, the integrated photocathode systems exhibit 7 hours operational stability. This work could shed light on designing and constructing efficient photocathode architecture for enabling practical solar-driven CO 2 reduction as a means of solar energy storage. An integrated Cu 2 O photocathode is designed for efficient and durable solar CO 2 reduction. The integrated device exhibits a solar-to-CO efficiency of 1.58% and quantum efficiency (QE) of 3.06%.