Decoupling Strategy for Enhanced Syngas Generation from Photoelectrochemical CO2 Reduction

Photoelectrochemical CO2 reduction into syngas (a mixture of CO and H-2) pro-vides a promising route to mitigate greenhouse gas emissions and store intermit-tent solar energy into value-added chemicals. Design of photoelectrode with high energy conversion efficiency and controllable syngas composition is of central importance but remains challenging. Herein, we report a decoupling strategy us-ing dual cocatalysts to tackle the challenge based on joint computational and experimental investigations. Density functional theory calculations indicate the optimization of syngas generation using a combination of fundamentally distinc-tive catalytic sites. Experimentally, by integrating spatially separated dual cocat-alysts of a CO-generating catalyst and a H-2-generating catalyst with GaN nano-wires on planar Si photocathode, we report a record high applied bias photon-to-current efficiency of 1.88% and controllable syngas products with tunable CO/H-2 ratios (0-10) under one-sun illumination. Moreover, unassisted solar CO2 reduction with a solar-to-syngas efficiency of 0.63% is demonstrated in a tan-dem photoelectrochemical cell.