W@Ag dendrites as efficient and durable electrocatalyst for solar-to-CO conversion using scalable photovoltaic-electrochemical system

The electrochemical conversion of CO₂ into CO using solar energy is the most efficient technique for artificial photosynthesis. However, many challenges remain, including the realisation of large-scale systems with high current density and stability. Herein, we report a carbon-supported tungsten-seed-based 3D silver dendrite (W@AgD) catalyst with abundant nanograin boundaries that exhibit enhanced CO₂ reduction (CO₂R) performance and stability. In zero-gap CO₂ electrolyzer, W@AgD showed outstanding catalytic activity with a maximum CO partial current density of 400 mA cm^–2 and stable operation for 100 h at 150 mA cm^–2. The 3D dendrites improve CO₂ mass transfer, while the abundant grain boundaries drive the Ag_xC_yO_z layer near the surface after activation, leading to superior CO₂R catalytic activity owing to the strong local electric fields. In a stand-alone photovoltaic-electrochemical system, we achieved a solar-to-CO efficiency (η_STC) of 12.1 % at 1 A. Thus, the synthesized catalyst and system are suitable for efficient solar energy storage.