Catalytic conversion of CO₂ to methane (CH₄) via the Sabatier reaction is an emerging strategy for mitigating anthropogenic CO₂ emissions while producing a versatile energy carrier. However, developing efficient, lowcost catalysts remains challenging, particularly in achieving stable, welldispersed supports with tunable surface chemistry. In a study published in ENG. Chem. Eng., researchers report a sustainable catalyst platform using biochar derived from date palm trunk (DPT) waste – a regionally abundant and underexplored biomass residue – as a support for Nibased CO₂ methanation catalysts.
The team prepared pristine biochar (UBC) by slow pyrolysis at 500 °C, then synthesized monometallic (Ni and Fe) and bimetallic (NiFe and NiK) catalysts via wet impregnation followed by pyrolysis. The biochar exhibited favorable micromesoporous characteristics with a BET surface area of 19 m²·g⁻¹, which increased significantly after metal incorporation – reaching 126 m²·g⁻¹ for BCNi3.0 (0.5 mmol Ni·g⁻¹) and 189 m²·g⁻¹ for BCNi7.0 (1.2 mmol Ni·g⁻¹). H4type hysteresis loops confirmed the presence of slitshaped micropores and mesopores. HRTEM showed Ni particle sizes of 6–11 nm for BCNi3.0, increasing to 8–21 nm at higher Ni loading. XPS and XRD confirmed that Ni exists predominantly as highly dispersed metallic Ni⁰, with NiFe catalysts forming NiFe₂O₄ and NiO phases.
Catalytic testing in a continuousflow reactor (H₂/CO₂ = 3, 1 bar, 300–600 °C) revealed that Ni loading strongly influences performance. BCNi3.0 achieved the optimal balance: 58 % CO₂ conversion and 91 % CH₄ selectivity at 400 °C. Increasing pressure to 30 bar enhanced conversion to 76 % and CH₄ selectivity to nearly 99 %, with stable operation over 20 h. Lower Ni loadings (BCNi0.5) showed reduced activity, while higher loadings (BCNi5.0, BCNi7.0) favored CO formation due to larger Ni particle sizes.
Bimetallic NiFe catalysts (Fe/Ni = 0.3) exhibited high CO selectivity (89 %) and suppressed CH₄ formation (10 %), indicating a shift toward the RWGS pathway. This behavior is attributed to Feinduced modification of Ni electronic properties and the formation of oxidic NiFe₂O₄ and NiO phases, which favor CO evolution. The postpyrolysis impregnated variant (BCFeNi0.3B) showed moderate CO selectivity (66 %) and higher CH₄ selectivity (33 %), implying weaker Ni–Fe interaction. Kpromoted Ni catalysts showed the lowest performance (24 % conversion, 37 % CH₄ selectivity), consistent with alkaliinduced suppression of methanation.
Notably, BCNi3.0 contains only 4.6 wt% Ni yet achieves performance comparable to or better than many literature catalysts requiring 10–40 wt% metal loading, while operating at a reduced H₂/CO₂ ratio of 3 (vs. stoichiometric 4). This highlights the efficient metal utilization enabled by the biochar support.
This work demonstrates that biochar from date palm trunk provides a sustainable, costeffective support for CO₂ methanation catalysts, with compositiondependent tuning of selectivity between methanation and RWGS pathways.

DOI
10.1007/s11705-026-2671-5