Continuous Solar-Driven CO2 Reduction to Liquid Oxygenates in a Scalable Photoelectrochemical Flow Cell

Abstract

The transition toward low-carbon chemical manufacturing requires scalable strategies to convert carbon emissions into value-added commodities independently of fossil feedstocks. Solar-driven photoelectrochemical (PEC) CO2 conversion represents a promising pathway, yet performance is frequently bottlenecked by poor mass transport and restricted device scalability.Herein, we report a versatile, modular, 3D-printed PEC flow reactor designed for continuous and scalable CO2 utilization. The system integrates a structurally engineered BiVO4/CoP photoanode for water oxidation with a highly selective Cu-coated gas diffusion electrode (Cu/GDL) cathode, operating at an active area of 1.6 cm 2 (substantially outscaling conventional millimeter-scale laboratory cells). Coupled with online micro-GC, benchtop NMR, and in-situ Raman spectroscopy, the integrated platform enables real-time product monitoring and molecular-level tracking of potential-dependent surface intermediates *COtop and *CObridge.Under optimized continuous-flow conditions, the reactor delivers a remarkable photocurrent density of 4.5 mA•cm -2 at 1.75 V, yielding an overall cathodic Faradaic Efficiency (FE) of 95%. Remarkably, the system channels selectivity predominantly toward high-value liquid oxygenates, achieving maximum FEs of 51.6% for acetate and 41.7% for methanol. Backed by over 100 hours of continuous operational stability with robust structural preservation of the electrodes, this work provides a scalable, technologically viable blueprint for efficient solar-tochemical conversion.