High‐Rate, Tunable Syngas Production with Artificial Photosynthetic Cells

Abstract

An artificial photosynthetic (APS) system consisting of a photoanodic semiconductor that harvests solar photons to split H2O, a Ni‐SNG cathodic catalyst for the dark reaction of CO2 reduction in a CO2‐saturated NaHCO3 solution, and a proton‐conducting membrane enabled syngas production from CO2 and H2O with solar‐to‐syngas energy‐conversion efficiency of up to 13.6 %. The syngas CO/H2 ratio was tunable between 1:2 and 5:1. Integration of the APS system with photovoltaic cells led to an impressive overall quantum efficiency of 6.29 % for syngas production. The largest turnover frequency of 529.5 h−1 was recorded with a photoanodic N‐TiO2 nanorod array for highly stable CO production. The CO‐evolution rate reached a maximum of 154.9 mmol g−1 h−1 in the dark compartment of the APS cell. Scanning electrochemical–atomic force microscopy showed the localization of electrons on the single‐nickel‐atom sites of the Ni‐SNG catalyst, thus confirming that the multielectron reduction of CO2 to CO was kinetically favored.

Synergistic effect of Co(II)-hole and Pt-electron cocatalysts for enhanced photocatalytic hydrogen evolution performance of P-doped g-C3N4

“…5(b) [46], the hydrogen electrode potentials (NHE) of g-C3N4 nanosheets and Co(II)/PCN-2 are determined as −0.67 and −0.53 V versus NHE, which are consistent with reported literatures [47]. Obviously, Co(II)/PCN-2 shows more positive flat-band potential than g-C3N4 nanosheets, which might be caused by the lower overpotential as well as splendid electronic conductivity of Co(II) [48,49].…”

Atomic‐Level Reactive Sites for Semiconductor‐Based Photocatalytic CO2 Reduction

“…Therefore, the different numbers of accumulated electrons on the reactive sites will lead to different pathways, and final products. Zhang et al investigated this factor of single Ni atoms and explored the collection and localization of electrons by electrochemical microscopy‐atomic force microscopy (SECM‐AFM). Results showed that the single nickel atom sites have a uniform capacity of electron storage, Figure 5 .…”

“…d) Current‐responsive image of Ni‐SNG reference with corresponding line profiles of topography and current. Reproduced with permission . Copyright 2019, Wiley‐VCH.…”

“…Atomic‐level reactive sites can be introduced into photocatalysts via a range of strategies such as: introducing vacancies in the crystal lattice, doping single heterogeneous atoms, anchoring functional groups and loading metal complexes on the surface, and fabricating FLPs . With advances in characterization technologies and synthesis methods, researchers can design materials from atomic level to reveal fundamental photocatalytic CO 2 reduction from spatial‐and‐time perspectives using, for, e.g., high resolution transmission electron microscope (HRTEM), scanning transmission electron microscopy (STEM), and in situ technologies.…”

Decoupling Strategy for Enhanced Syngas Generation from Photoelectrochemical CO2 Reduction

“…The efficiency is higher than recently reported values in a PEC cell without external bias ( Li et al., 2019 ; Andrei et al., 2020 ). Although the efficiency is lower than that reported in photovoltaic-electrolysis (PV-E) system ( Schreier et al., 2015a , 2017 ; Urbain et al., 2017 ; Zhang et al., 2019 ; Kim et al., 2019 ; Cheng et al., 2020 ), the PEC approach integrates the light harvesting and electrochemical process of PV-E process into a single and monolithic device via a direct semiconductor-electrolyte interface, providing potential advantages over the PV-E system in terms of cost and complexity. And it is expected that the STS efficiency of the PEC system could be enhanced further by employing better photoanode with higher photocurrent at the low bias region, which would improve the overlap of J-V curves between photocathode and photoanode.…”