Mechanically Enhanced Catalytic Reduction of Carbon Dioxide over Defect Hexagonal Boron Nitride

Abstract

The hydrogenation of waste gas carbon dioxide into value added molecules could reduce greenhouse gas emissions and our dependence on nonrenewable energy sources. Catalytic paths toward this goal typically involve high pressures and low abundance transition metal catalysts. Here, we have found that vacancies induced in defect-laden hexagonal boron nitride (dh-BN) can effectively activate the CO₂ molecule for hydrogenation. Subsequent hydrogenation to formic acid (HCOOH) and methanol (CH₃OH) occur through vacancy facilitated coadsorption of hydrogen and CO₂. More importantly, we find that dh-BN catalyzes formic acid formation observable at reaction temperatures above 160 °C and pressures of 583 kPa, while methanol formation is observed at lower temperatures (as low as 20 °C). Methanol formation occurs with a TOF of 1.52 × 10–² s–¹ and TON of 289 at 20 °C. Carbon dioxide (CO₂) is a major greenhouse gas and the main component of all combustion products produced in power generation and transportation. In addition, boron and nitrogen are abundant elements and thus, catalysts prepared from h-BN would allow catalytic recovery of value-added molecules facilitating efforts to reduce the emissions of this gas.