Excellent Pd supported on carbon catalysts for the dehydrogenation of formic acid were synthesized from a lignocellulosic biomass residue. The preparation of the carbon support consisted of a H 3 PO 4 -assisted hydrothermal carbonization (HTC) and activation of a hemp residue and subsequent nitrogen functionalization. It was observed that the presence of nitrogen groups influenced both the size and the electronic properties of the Pd nanoparticles, which ultimately affected their catalytic properties. Furthermore, the catalytic performance also depended on the synthesis conditions used in the preparation of the catalysts (i.e., reduction of the Pd nanoparticles with NaBH 4 prior to the catalytic test or in situ reduction). The best-performance catalysts (Pd/N-HTC (n.r.)), which were prepared by in situ reduction of the nanoparticles, displayed a remarkable catalytic activity with a very high TOF number of 8365 h −1 (TOF value calculated for the 2nd catalytic run and expressed per surface Pd atom) and outstanding stability during 6 consecutive reaction cycles, although the initial activity is maintained for 12 cycles. The catalytic system studied is among the most stable ever reported Pd-based heterogeneous catalysts for the dehydrogenation of formic acid.

Biomass upgrading is a promising approach to face the current energy consumption and chemicals production. Lignocellulosic biomass residues have taken the lead in this field. In this study, hemp residue-based activated carbons (ACs) were prepared by H3PO4-assisted hydrothermal carbonization (HTC) using a low concentration of H3PO4 (25 wt. %). ACs with a high porosity development were obtained (SBET>1200 m 2 g-1), and they were subsequently functionalized with nitrogen groups using mild conditions. As-synthesized ACs were also heat-treated to enhance the electrical conductivity, improving the electrochemical performance. As a proof of concept, electrochemical capacitors (ECs) based on as-prepared ACs in aqueous and organic electrolytes, showing energy densities comparable to those of a capacitor based on an AC used in commercial capacitors. The most attractive outcome of this study is the straightforward, cost-effective, and sustainable methodology to prepare high added-value functional ACs with great potential for energy and environmental applications.

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