Size‐Dependent Selectivity of Electrochemical CO₂ Reduction on Converted In₂O₃ Nanocrystals

Abstract

The size modulation of catalyst particles represents a useful dimension to tune catalytic performances by impacting not only their surface areas but also local electronic structures. It, however, has remained inadequately explored and poorly elucidated. Here, we report the interesting size‐dependent selectivity of electrochemical CO2 reduction on In2O3 nanocrystals. 5‐nm nanoparticles and 15‐nm nanocubes with focused size distribution are prepared via a facile solvothermal reaction in oleylamine by carefully controlling a set of experimental parameters. They serve as the precatalysts, and are reduced to In nanocrystals while largely inherit the original size feature during electrochemical CO2 reduction. Catalyst derived from 15‐nm nanocubes exhibits greater formate selectivity (>95 %) at lower overpotential and negligible side reactions compared to bulk‐like samples (indium foil and 200‐nm cubes) as well as the catalyst derived from smaller 5‐nm nanoparticles. This unique size dependence is rationalized as a result of the competition among different reaction pathways by our theoretical computations. Smaller is not always better in the catalyst design.

Isotype Heterojunction-Boosted CO2 Photoreduction to CO

“…More recently, a high solar-to-hydrogen conversion efficiency of 1.16% was reported over an isotype heterojunctions consisting of boron-doped and nitrogen-deficient g-C 3 N 4 [19]. These encouraging achievements indicate the superior photocatalytic properties of isotype heterojunctions, which are highly desirable for improving the performance of photocatalytic CRR [26][27][28][29][30]. However, up to date, no studies have reported photocatalytic CRR over isotype heterojunctions.…”

Highly Dispersed Indium Oxide Nanoparticles Supported on Carbon Nanorods Enabling Efficient Electrochemical CO2 Reduction

“…[22] Excellent faradaic efficiency toward formate (>90%) has been achieved in literatures. [23][24][25][26][27] Albeit with recent advances, it remains challenging to devise In-based catalysts having high formate partial current density without compromise to selectivity. To this end, designing nanostructured catalysts with high-density and undercoordinated active sites is highly desirable.…”

Selectivity of Electrochemical CO2Reduction on Metal Electrodes: The Role of the Surface Oxidized Layer

“…In the previous studies, the reaction free energies of *COOH and *OCHO species were commonly used as the descriptors to explain the reaction trends. − The relation between Δ G (*COOH) and Δ G (*OCHO) was first examined for various metals and oxides. The η 2 (C,O)-CO 2 H and η 1 (C)-CO 2 H chemisorption structures were considered for *COOH intermediate and the η 2 (O,O)-HCO 2 structure for *OCHO intermediate (the optimized adsorption structures are given in Figure S1).…”

“…Deriving from this concept, Jaramillo et al examined the relations between the binding energies of intermediates (*COOH and *OCHO) and the partial current densities of the products ( j CO and j HCOOH ) for CO 2 reduction, in which Sn and Au metals were found on the apex of volcano plots for formic acid and CO products, respectively . Hitherto, the *COOH and *OCHO intermediates, which are considered the key intermediates in the processes of CO and formic acid production, respectively, are widely applied in explaining the performance of catalysts theoretically. − The BEP relation has been successfully applied to the reactions with the same/analogous mechanisms (e.g., comparing the CO evolution activity of different surfaces through the binding energy of *COOH) . However, due to the different formation mechanisms of the *COOH (protonation of oxygen) and *OCHO (protonation of carbon) intermediates, the reaction tendency toward CO and HCOOH might not be predicted by simply comparing the energies of these two species.…”