High-Performance, Scalable, and Low-Cost Copper Hydroxyapatite for Photothermal CO2 Reduction

Abstract

Catalytic reduction of carbon dioxide is a promising strategy for mitigating global carbon emissions. In particular, the abundant and nontoxic material hydroxyapatite demonstrates high activity at a low cost when its constituent cations are replaced with transition metals, which also enables its catalytic properties to be tailored. Using this method, the facile and scalable synthesis of a coppersubstituted hydroxyapatite catalyst is presented, demonstrating its high activity in the reverse water gas shift reaction. Thorough in situ characterization using X-ray absorption and Fourier transform infrared spectroscopic methods provides unrivaled insight into both the structure of the active catalyst and the speciation of reaction intermediates. It is thus shown that this copper-substituted hydroxyapatite catalyst is an exemplary candidate for use in large-scale carbon dioxide reduction systems.

Construction of New Active Sites: Cu Substitution Enabled Surface Frustrated Lewis Pairs over Calcium Hydroxyapatite for CO2 Hydrogenation

“…[9b] No HPO 4 2− peaks were observed at 3235, 1235, 831 cm −1 at high temperatures, indicating PO 4 3− was not involved in the hydrogen activation on SFLPs. [6,10] These results indicate that H 2 is undergoing heterolysis on proximal Lewis acidic Cu 2+ and Lewis basic OH − SFLPs to form CuH − /Ca-OH 2 + surface sites.…”

“…The peaks located at 1704, 1655, 1624, 1555, 1433, and 1383 cm −1 can be attributed to bicarbonate intermediates. [ 6 , 9 , 11 ] For peaks at 2859, 1611, and 1584 cm −1 , correspond to vibrational modes of formate species. [ 6 , 11 , 12 ] The decrease of CO 2 peak (3600–3800 cm −1 ) intensity reflected an enhanced CO 2 activation over 0.5 mol% Cu‐HAP with Cu 2+ substitution.…”

“…[ 6 , 9 , 11 ] For peaks at 2859, 1611, and 1584 cm −1 , correspond to vibrational modes of formate species. [ 6 , 11 , 12 ] The decrease of CO 2 peak (3600–3800 cm −1 ) intensity reflected an enhanced CO 2 activation over 0.5 mol% Cu‐HAP with Cu 2+ substitution. [ 2 , 6 ] The growth of intense vibrational modes in hydroxyl stretching and deformation region also confirmed the enhanced CO 2 activation, as well as the higher H 2 adsorption capacity (Figure S8 , Supporting Information).…”

Improvement of CO2 Photoreduction Efficiency by Process Intensification

“…Ozin et al [40] recorded the temperature dependence of the thermal and photothermal CO 2 reduction, i.e., the CO 2 reduction driven by photothermal and thermal effect only. A clear light effect appeared at 120 • C and increased continually to 300 • C, which enhanced reaction rates and decreased the observed activation energy.…”

Nanostructured Photothermal Materials for Environmental and Catalytic Applications

“…With the emergence of photothermal effects as the strong development potential in environmental and energy catalysis, many efforts have been focused on nanostructured photothermal materials. Up to now, nanomaterials focusing on the application of photothermal effects of plasmonic structures [24], photothermal catalytic hydrogenation reactions [25,26], photothermal catalytic CO 2 reduction [21,27,28], and photothermal seawater evaporation [29,30] have been separately reviewed. However, these reviews provide only a one-sided overview of photothermal nanomaterials.…”