Biochar assembled Ni atom-clusters for hydrogen-free and solvent-free deoxygenation of fatty acids

Upgrading biomass-derived fatty acids through the H₂-free and solvent-free catalytic deoxygenation process is both safe and eco-friendly. Herein, we used modified rice husk-derived biochar with ultra-high specific surface area and abundant surface groups as a support to design a homologous bimetallic site catalyst containing Ni single atoms (Ni₁) and Ni nanoclusters (Ni_n), the synergy between which is dedicated to excellent catalytic performance. The designed catalyst, Ni_1+n/A-bio-AC, demonstrated an impressive 89.8% selectivity for odd-numbered long-chain alkanes during the H₂-free and solvent-free deoxygenation of stearic acid, with a turnover frequency value over 18 times higher than conventional Ni/AC. Multiple characterizations revealed the coexistence of Ni₁ and Ni_n on the catalyst support. Experimental and theoretical calculations showed that Ni_n facilitates the adsorption of fatty acid substrates. While Ni₁ serves as highly dispersed Lewis acid sites, enhancing the dehydrogenation of fatty alcohol intermediates during the in situ hydrodeoxygenation and lowering the decarboxylation pathway energy barriers via electronic synergy with Ni_n, thus remarkably boosting the catalytic deoxygenation activity. This work provides a novel Ni dual-site catalyst for developing biomass resource conversion technologies.