Metal-Free N, P-Codoped Carbon for Syngas Production with Tunable Composition via CO2 Electrolysis: Addressing the Competition Between CO2 Reduction and H2 Evolution

Electroreduction of carbon dioxide into value-added fine chemicals is a promising technique to realize the carbon cycle. Recently, metal-free heteroatom doped carbons are proposed as promising cost-effective electrocatalysts for CO2 reduction reaction (CO2RR). However, the lack of understanding of the active site prevents the realization of a high-performance electrocatalyst for the CO2RR. Herein, we synthesized metal-free N, P co-doped carbons (NPCs) for producing syngas, which is composed of H2 and CO, by CO2 electrolysis using inexpensive bio-based raw materials via simple pyrolysis. The syngas ratio (H2/CO) can be controlled within the high demand range (0.3-4) at low potentials using NPCs by tuning the N and P contents. In comparison with only N doping or P doping, N and P co-doping has a positive impact on improving CO2RR activity. Experimental analysis and density functional theory (DFT) calculations revealed that negatively charged C atoms adjacent to N and P atoms are the most favorable active sites for CO2-to-CO conversion compared to pyridinic N on N, P co-doped carbon. Introducing N atoms generates the preferable CO2 adsorption site, and P atoms contribute to decreasing the Gibbs free energy barrier for key *COOH intermediates adsorbed on the negatively charged C atoms.

Insight into the Active Sites of N,P-Codoped Carbon Materials for Electrocatalytic CO2 Reduction

Doping heteroatoms in carbon materials is a promising method to prepare the robust electrocatalysts for the carbon dioxide reduction reaction (CO₂RR), which is beneficial for sustainable energy storage and environmental remediation. However, the obscure recognition of active sites is the obstacle for further development of high-efficiency electrocatalysts, especially for the N,P-codoped carbon materials. Herein, a series of N,P-codoped carbon materials (CNP) is prepared with different N and P contents to explore the relationship between the N/P configuration and the CO₂RR activity. As compared with the N-doped carbon materials, the additional P doping is helpful to improve the activity. The optimum N,P-codoped carbon materials (CNP-900) achieve 80.8% CO Faradaic efficiency (FE_CO) at a mild overpotential of 0.44 V. On the basis of the X-ray photoelectron spectroscopy results, the suitable ratio between pyridinic N and graphitic N and the least P-N content are beneficial for CO₂RR. The density functional theory calculations further illustrate that two elementary steps to form *COOH and *CO in CO₂RR are determined by the graphitic N and pyridinic N configurations, respectively. The existence of the P-N configuration breaks the equilibrium between graphitic N and pyridinic N to suppress the activity.

Metal-Organic Frameworks Derived Electrocatalysts for Oxygen and Carbon Dioxide Reduction Reaction

The increasing demands of energy and environmental concerns have motivated researchers to cultivate renewable energy resources for replacing conventional fossil fuels. The modern energy conversion and storage devices required high efficient and stable electrocatalysts to fulfil the market demands. In previous years, we are witness for considerable developments of scientific attention in Metal-organic Frameworks (MOFs) and their derived nanomaterials in electrocatalysis. In current review article, we have discussed the progress of optimistic strategies and approaches for the manufacturing of MOF-derived functional materials and their presentation as electrocatalysts for significant energy related reactions. MOFs functioning as a self-sacrificing template bid different benefits for the preparation of metal nanostructures, metal oxides and carbon-abundant materials promoting through the porous structure, organic functionalities, abundance of metal sites and large surface area. Thorough study for the recent advancement in the MOF-derived materials, metal-coordinated N-doped carbons with single-atom active sites are emerging candidates for future commercial applications. However, there are some tasks that should be addressed, to attain improved, appreciative and controlled structural parameters for catalytic and chemical behavior.

From CO2 to Value-Added Products: A Review about Carbon-Based Materials for Electro-Chemical CO2 Conversion

The global warming and the dangerous climate change arising from the massive emission of CO2 from the burning of fossil fuels have motivated the search for alternative clean and sustainable energy sources. However, the industrial development and population necessities make the decoupling of economic growth from fossil fuels unimaginable and, consequently, the capture and conversion of CO2 to fuels seems to be, nowadays, one of the most promising and attractive solutions in a world with high energy demand. In this respect, the electrochemical CO2 conversion using renewable electricity provides a promising solution. However, faradaic efficiency of common electro-catalysts is low, and therefore, the design of highly selective, energy-efficient, and cost-effective electrocatalysts is critical. Carbon-based materials present some advantages such as relatively low cost and renewability, excellent electrical conductivity, and tunable textural and chemical surface, which show them as competitive materials for the electro-reduction of CO2. In this review, an overview of the recent progress of carbon-based electro-catalysts in the conversion of CO2 to valuable products is presented, focusing on the role of the different carbon properties, which provides a useful understanding for the materials design progress in this field. Development opportunities and challenges in the field are also summarized.