The continuously increasing CO2 released from human activities poses a great threat to human survival by fluctuating global climate and disturbing carbon balance among the four reservoirs of the biosphere, earth, air, and water. Converting CO2 to value-added feedstocks via electrocatalysis of the CO2 reduction reaction (CO2RR) has been regarded as one of the most attractive routes to re-balance the carbon cycle, thanks to its multiple advantages of mild operating conditions, easy handling, tunable products and the potential of synergy with the rapidly increasing renewable energy (i.e., solar, wind). Instead of focusing on a special topic of electrocatalysts for the CO2RR that have been extensively reviewed elsewhere, we herein present a rather comprehensive review of the recent research progress, in the view of associated value-added products upon selective electrocatalytic CO2 conversion. We initially provide an overview of the history and the fundamental science regarding the electrocatalytic CO2RR, with a special introduction to the design, preparation, and performance evaluation of electrocatalysts, the factors influencing the CO2RR, and the associated theoretical calculations. Emphasis will then be given to the emerging trends of selective electrocatalytic conversion of CO2 into a variety of value-added products. The structure-performance relationship and mechanism will also be discussed and investigated. The outlooks for CO2 electrocatalysis, including the challenges and opportunities in the development of new electrocatalysts, electrolyzers, the recently rising operando fundamental studies, and the feasibility of industrial applications are finally summarized.

Electrocatalysis for CO2 conversion: from fundamentals to value-added products

Nanomaterials for photoelectrochemical water splitting - review

Inside-and-Out Semiconductor Engineering for CO2 Photoreduction: From Recent Advances to New Trends

The conversion of carbon dioxide (CO2) into fuels and value-added products is one of the most significant inventions to address the global warming and energy needs. Photoelectrochemical (PEC) CO2 c...

Photoelectrochemical Conversion of Carbon Dioxide (CO2) into Fuels and Value-Added Products

The photolysis of nitrous acid (HONO) in the early morning hours is an important source of OH radicals, the most important daytime oxidizing species. Although the importance of this mechanism has been recognized for many years, no accurate quantification of this OH source is available, and the role of HONO photolysis is often underestimated. We present measurements of HONO and its precursor NO 2 by Differential Optical Absorption Spectroscopy (DOAS) during the Berliner Ozonexperiment (BERLIOZ) field campaign in July/August 1998 at Pabstthum near Berlin, Germany. HONO concentrations, formation rates, and simultaneously measured HONO photolysis frequencies are used to calculate the total amount of OH formed by HONO photolysis during a full diurnal cycle. A comparison with the OH formation by photolysis of O 3 and HCHO and by the reaction of alkenes with ozone shows that HONO photolysis contributed up to 20% of the total OH formed in a 24 hour period during this campaign. In the morning hours, HONO photolysis was by far the most important OH source during BERLIOZ.

OH formation by HONO photolysis during the BERLIOZ experiment : Photochemistry experiment in BERLIOZ (PHOEBE)

Complete Photocatalytic Mineralization of Microplastic on TiO2 Nanoparticle Film

Visible-light-driven photoelectrochemical (PEC) catalysis has been widely studied as a promising technique for the degradation of organic pollutants in wastewater. Herein, we report a sulfite-enhanced PEC degradation process for the degradation of organic pollutant. The degradation rate was significantly enhanced by ～30 times with the addition of 16 mM sulfite. The Electron Spin Resonance (ESR), Transient Absorption (TA) and hole scavenger studies showed that sulfite radicals ( S O 3 ⦁ - ) were the main reactive species in the reactions. The pollutant degradation pathway was studied by in-situ techniques and mass spectrometer, showing that the sulfite addition can promote the cleavage of aromatic ring C C bond and C N bond.

Significantly accelerated PEC degradation of organic pollutant with addition of sulfite and mechanism study

Highly efficient CO2 reduction on ordered porous Cu electrode derived from Cu2O inverse opals

Simultaneous SO2 removal and CO2 reduction in a nano-BiVO4|Cu-In nanoalloy photoelectrochemical cell

Conversion of CO2 into fuels and chemicals via electroreduction has attracted significant interest. Via mesostructure design to tune the electric field distribution in the electrode, it is demonstrated that the Cu–In alloy with an inverse opal (CI-1-IO) structure provides efficient electrochemical CO2 reduction and allows for sensitive detection of the CO2 reduction intermediates via surface-enhanced Raman scattering. The significant enhancement of Raman signals of the intermediates on the CI-1-IO surface can be attributed to electric field enhancement on the “hot edges” of the inverse opal structure. Additionally, a highest CO2 reduction faradaic efficiency (FE) of 92% (sum of formate and CO) is achieved at −0.6 V vs. RHE on the CI-1-IO electrode. The diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) results show that the Cu–In alloy with an inverse opal structure has faster adsorption kinetics and higher adsorption capacity for CO2. The “hot edges” of the bowl-like structure concentrate electric fields, due to the high curvature, and also concentrate K+ on the active sites, which can lower the energy barrier of the CO2 reduction reaction. This research provides new insight into the design of materials for efficient CO2 conversion and the detection of intermediates during the CO2 reduction process.

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Yangyang Liu

Papers

Complete Photocatalytic Mineralization of Microplastic on TiO2 Nanoparticle Film

Significantly accelerated PEC degradation of organic pollutant with addition of sulfite and mechanism study

Highly efficient CO2 reduction on ordered porous Cu electrode derived from Cu2O inverse opals

Simultaneous SO2 removal and CO2 reduction in a nano-BiVO4|Cu-In nanoalloy photoelectrochemical cell

“Hot edges” in an inverse opal structure enable efficient CO2 electrochemical reduction and sensitive in situ Raman characterization