High-Photovoltage Silicon Nanowire for Biological Cofactor Production.

Photocathodic conversion of NAD to NADH cofactor is a promising platform for activating redox biological catalysts and enzymatic synthesis using renewable solar energy. However, many photocathodes suffer from low photovoltage, consequently requiring a high cathodic bias for NADH production. Here, we report an np-type silicon nanowire (np-SiNW) photocathode having a photovoltage of 435 mV to drive energy-efficient NADH production. The enhanced band bending at the n/p interface accounts for the high photovoltage, which conduces to a benchmark onset potential [0.393 V vs the reversible hydrogen electrode (V)] for SiNW-based photocathodic NADH generation. In addition, the np-SiNW nanomaterial exhibits a Faradaic efficiency of 84.7% and a conversion rate of 1.63 μmol h cm at 0.2 V, which is the lowest cathodic potential to achieve the maximum productivity among SiNW-sensitized cofactor production.