CO₂ Overall Splitting by a Bifunctional Metal‐Free Electrocatalyst

Abstract

Photo/electrochemical CO2 splitting is impeded by the low cost‐effective catalysts for key reactions: CO2 reduction (CDRR) and water oxidation. A porous silicon and nitrogen co‐doped carbon (SiNC) nanomaterial by a facile pyrolyzation was developed as a metal‐free bifunctional electrocatalyst. CO2‐to‐CO and oxygen evolution (OER) partial current density under neutral conditions were enhanced by two orders of magnitude in the Tafel regime on SiNC relative to single‐doped comparisons beyond their specific area gap. The photovoltaic‐driven CO2 splitting device with SiNC electrodes imitating photosynthesis yielded an overall solar‐to‐chemical efficiency of advanced 12.5 % (by multiplying energy efficiency of CO2 splitting cell and photovoltaic device) at only 650 mV overpotential. Mechanism studies suggested the elastic electron structure of −Si(O)−C−N− unit in SiNC as the highly active site for CDRR and OER simultaneously by lowering the free energy of CDRR and OER intermediates adsorption.

Single‐Atom Electrocatalysts from Multivariate Metal–Organic Frameworks for Highly Selective Reduction of CO2 at Low Pressures

“…[27][28][29] In addition to the active site identification, another critical issue in CO 2 RR is the energy-consuming capture and purification process of CO 2 .Specifically speaking,toachieve high selectivity,t he currently reported CO 2 RR are generally performed in pure CO 2 . [30][31][32][33][34][35][36][37][38][39][40][41][42] However,t he actual concentration of CO 2 feedstock available from industrial processes such as coal power plant (5-15 %CO 2 )and steel/petrochemical industry (14-33 %C O 2 )i sr elatively low. [43][44][45] Given the thermodynamic stability of the C = Obond ( % 806 kJ mol À1 )of CO 2 and its limited solubility in aqueous solution, low CO 2 concentration will significantly affect the activity,setting great barriers for the direct CO 2 utilization.…”

Online Monitoring of Electrochemical Carbon Corrosion in Alkaline Electrolytes by Differential Electrochemical Mass Spectrometry

“…carbon nanotubes and graphene), carbon fibers,c arbon foils and pastes,a mong others,a re extensively employed in electrochemical technologies.I ne lectrocatalysis,c arbon is used as support for dispersion of precious-metal catalyst nanoparticles to enhance their utilization, and as aconductive matrix to boost charge transfer of inherently low-conductivity catalysts. [1] Recent developments of so-called heteroatomdoped carbon catalysts or catalyst supports,f or example, nitrogen-, boron-, or phosphorus-doped carbon, has revealed interesting new applications of such carbon-based materials as noble-metal-free catalysts for the oxygen reduction reaction (ORR), [2] the oxygen evolution reaction (OER), [3] and the CO 2 reduction reaction (CO 2 RR), [4] to name but afew.A core concern of using glassy carbon electrodes [5] and carbon as an electrode material, catalyst, or catalyst support in electrochemical systems in general relates to its susceptibility to corrode under oxidizing conditions [6,7] through dissolution, gasification, or exfoliation under formation of corrosion products that affect the carbon properties.I nt he past three decades,s tudies on carbon corrosion predominantly focused on acidic electrolytes, [8][9][10] mainly because of the broad research interest in proton exchange membrane fuel cells (PEMFCs) and electrolyzers.C arbon corrosion was intensively studied using various analytical techniques,i ncluding Raman spectroscopy, [11] FT-IR spectroscopy, [12] X-ray diffractometry, [11] X-ray photoelectron spectroscopy, [13] and identical location transmission electron microscopy. [14] Carbon becomes thermodynamically unstable at potentials higher than its equilibrium potential of 0.207 Vv ersus reversible hydrogen electrode (RHE).…”

Online‐Bestimmung der elektrochemischen Kohlenstoffkorrosion in alkalischen Elektrolyten durch differentielle elektrochemische Massenspektrometrie

“…In der Elektrokatalyse wird Kohlenstoff als Tr äger fürd ie Dispersion von Edelmetallkatalysator-Nanopartikeln zur Verbesserung ihrer Aktivitätu nd als leitfähige Matrix zur Erhçhung des Ladungstransfers von Katalysatoren mit inhärent niedriger Leitfähigkeit verwendet. [1] Jüngste Entwicklungen sogenannter Heteroatom-dotierter Kohlenstoffkatalysatoren oder Katalysatorträger,z .B.S tickstoff-, Bor-o der Phosphordotierter Kohlenstoff,haben interessante neue Anwendungen solcher kohlenstoffbasierter Materialien als edelmetallfreie Katalysatoren für, um nur einige zu nennen, die Sauerstoffreduktionsreaktion (ORR), [2] die Sauerstoffevolutionsreaktion (OER) [3] sowie die CO 2 -Reduktionsreaktion (CO 2 RR) [4] erschlossen. Ein zentrales Anliegen bei der Verwendung von Glaskohlenstoffelektroden [5] und Kohlenstoff als Elektrodenmaterial, Katalysator oder Katalysatorträger in elektrochemischen Systemen bezieht sich auf seine Anfälligkeit für Korrosion unter oxidierenden Bedingungen [6,7] durch Auflçsung, Vergasung oder Abblättern unter Bildung von Korrosionsprodukten, welche die Kohlenstoffeigenschaften beeinflussen.…”

“…Die CO-Bildung wird aufgrund ihres hohen Standardpotentials thermodynamisch behindert, während die CO-Oxidation zu CO 2 mit einem Standardpotential von E 0 = À0.103 V SHE bevorzugt wird [Gl. (3)].…”