Hydrogen production from formic acid is a promising route for clean energy, but it requires catalysts that are both active, selective, and stable. Here, we explore how nitrogen doping of the carbon support and interaction with silver tune the performance of Pd catalysts. Using XPS and EXAFS, we show that nitrogen groups promote the formation of Pd2+ species, decrease the Pd coordination number, and stabilize small nanoparticles that remain highly dispersed after reaction. The basic character of the doped carbon support also enhances interactions with key intermediates, contributing to the exceptional stability of these catalysts. In contrast, introducing Ag into Pd nanoparticles changes the electronic environment of Pd, as indicated by charge transfer in XPS and Pdsingle bondAg interactions detected by EXAFS, leading to a notable increase in catalytic activity. DFT calculations identify H2 desorption as the rate-limiting step and reveal that both electron density withdrawn by nitrogen atoms and the electron transfer of Ag ultimately weaken the Pdsingle bondH bond. Despite their opposite electronic effects, both modifications facilitate H2 release and boost the overall reaction rate. Taken together, our results show that nitrogen primarily enhances stability, while silver mainly increases activity, and that combining both provides a rational strategy for designing next-generation Pd catalysts for efficient hydrogen generation from formic acid.

The use of biomass in the energy landscape has aroused great interest because of the diversity of high-value-added products that can be obtained. Among them, carbon materials stand out for properties such as their high chemical and thermal stability, large specific surface area, and possibility of modifying their surface properties by introducing heteroatoms, which make them ideal candidates for countless applications. The present review addresses to some of the representative works related to the preparation of advanced carbon materials prepared from biomass residues for applications of environmental interest, such as environmental remediation, catalytic processes, and energy-related devices.

Glycerine, a by-product of diverse industrial processes, is a promising platform molecule for biorefineries, but its use is hindered by the presence of impurities in its crude form. Adsorption represents a low-cost and versatile purification strategy; however, systematic studies addressing glycerine adsorption on carbon materials (CMs) and its desorption remain scarce. This work investigates the influence of porosity and surface chemistry on glycerine adsorption from aqueous solutions and its subsequent thermal desorption using a wide range of CMs, including commercial activated carbons, biochars, and thermally treated carbons with selectively modified oxygen surface groups while preserving their porous texture. Glycerine uptake strongly depends on the properties of the CMs. The highest adsorption capacities, reaching up to 121 wt% (121 g of glycerine retained per 100 g of carbon) under the studied conditions, are obtained for carbons combining well-developed microporosity and rich surface chemistry. Glycerine retention occurs through confinement within micropores and weak interactions with surface functional groups. Concerning desorption, glycerine weakly associated with oxygenated surface groups can be released at moderate temperatures (around 210 °C), while glycerine confined in micropores requires higher temperatures for complete desorption. Porosity and surface chemistry also determine whether desorption proceeds uniformly or in multiple steps. Overall, these results elucidate the combined role of porosity and surface chemistry in glycerine adsorption-desorption and provide guidelines for the design of tailored CMs adsorbents. CMs with high narrow microporosity, and suitably tuned oxygen surface chemistry emerge as particularly attractive candidates for effective glycerine purification and recovery with feasible regeneration.

In this work, we demonstrate the importance of developing cost-effective systems by optimizing the amount of Cu species loaded on TiO2 to attain good catalytic activity towards the photoreduction of CO2 into valuable chemical products using H2O as hydrogen source and ethanol (EtOH) as a hole scavenger. A catalyst bearing only a nominal 0.5 wt.% of Cu (real loading 0.3 wt.%) presents an outstanding average methane production yield of 845 µmol CH4·gcat-1·h-1, which is higher than that achieved by the counterpart sample loaded with a nominal 1 wt.% (811 µmol CH4·gcat-1·h-1) or 5 wt.% (470 µmol CH4·gcat-1·h-1). The samples were characterized physicochemically to reveal the Cu speciation, and the role of the Cu species is critical in the photocatalytic performance. The results remark that the oxidation state and the size of the nanoparticles together with the interaction of all reagents with the photocatalyst surface are key to understand in the photocatalytic performance of the designed heterostructure.

This file contains the data of the manuscript Enhanced Thermo-Photocatalytic CO₂ Reduction to CH₄ over Cu-Modified TiO₂-Based Catalysts submitted for publication in Nanomaterials journal.

Metal-free nitrogen-doped carbon materials are promising electrocatalysts towards oxygen reduction reaction (ORR), yet the nature of the active sites remains under debate. Previous investigations based on ex situ X-ray photoelectron spectroscopy (XPS) characterization and computational modelling studied the role of graphitic N species in ORR and suggested that these species at the carbon edges are the most active site towards ORR in alkaline conditions and pyridone type groups (N-C-O) may be formed as ORR intermediates. However, these findings are limited by the ex situ XPS measurement approach. Air exposure and vacuum treatment can alter oxidation states and surface adsorbates, hindering direct correlation with electrochemical performance. In addition, short-lived reaction intermediates that form under in situ conditions are inherently transient and are therefore not captured by ex situ measurements, leading to an incomplete representation of the active surface during electrochemical operation. Sensitivity of the ex situ XPS can also be a challenge. To overcome these limitations, we report the first in situ investigation of N-doped metal free electrocatalysts using near-ambient pressure XPS (NAP-XPS) under highly controlled electrochemical conditions at a synchrotron source. This in situ approach enables the dynamic evolution of nitrogen species as a function of applied potential and electrolyte environment (acidic and alkaline) under close to realistic ORR conditions, allowing previously proposed active-site assignments to be critically evaluated. The use of this technique opens the door to studying carbon-based electrocatalysts with different functionalities under operating conditions, with the aim of gaining a more detailed understanding of the reaction mechanism.

This review intends, in a critical way, the comprehensive view of the importance of porous carbons surface chemistry for their applications in an energy–environment nexus. Surface chemistry is presented as a combination of functional heteroatom-containing groups, dopants, and structural defects. First, we briefly address carbon surface chemical environment and the methods of its modification and characterization, indicating their practical limitations. Then, the effects of surface chemistry on separation, catalysis, energy storage, sensing and microwave absorption are introduced. Besides a critical analysis of published findings on these topics, we also include our views on the advancement in the processes which rely on porous carbons surface chemistry, and identify strategic areas and directions that should deserve further attention. We focus on new findings and important original contributions to the field. Since the community of carbon researchers grows following the strategic application of these materials, the role of functional groups, dopants and structural defects in various cutting-edge applications is emphasized, showing the progress in the field and the evolution of findings. A clear determination of the effects of carbon surface is often a challenge since carbons porosity and the locations of specific bonds/sites/defects in the carbon texture provide nanoconfinement effects.

To produce hydrogen and revalorize lignocellulosic residues, Cu/TiO2 and Ni/TiO2 photocatalysts (metal loading 1 or 5 wt%), as-prepared and after thermal reduction treatment, were tested for the photoreforming of cellulose and almond shell derived-substrates. Net photoreforming contributions were quantified by subtracting the individual contributions of photodegradation and photocatalyzed water splitting. Only milled cellulose (MC) and the liquid from the hydrothermal carbonization of milled almond shell (HMAS-L2) substrates proved effective for photoreforming, yielding significantly higher hydrogen productions than those obtained from substrates photodegradation and water splitting. As-prepared Cu/TiO2 showed efficient photocatalytic activity due to the facile in-situ reduction of Cu species. Conversely, Ni/TiO2 photocatalysts became active only after the reduction treatment, when partial formation of Ni0 species enhanced charge separation. The presence of reduced metals significantly improved photoactivity by decreasing charge recombination. The highest hydrogen productions reached were 2320 μmol·gcat−1· h−1 and 2440 μmol·gcat−1·h−1 with MC_5Ni-P25-r and HMAS-L2_5Cu/P25-r, respectively, surpassing previously reported literature values. The H2/CO2 molar ratios, with values close to the theoretical stoichiometric ratio (≈2), confirmed the predominant photoreforming pathway, while deviations indicated concurrent photodegradation and/or photoinduced water splitting. Tests with scavengers confirmed the effective photoreforming with MC and HMAS-L2 substrates, in contrast to milled almond shell and its derived solids.

To produce hydrogen and revalorize lignocellulosic residues, Cu/TiO2 and Ni/TiO2 photocatalysts (metal loading 1 or 5 wt%), as-prepared and after thermal reduction treatment, were tested for the photoreforming of cellulose and almond shell derived-substrates. Net photoreforming contributions were quantified by subtracting the individual contributions of photodegradation and photocatalyzed water splitting. Only milled cellulose (MC) and the liquid from the hydrothermal carbonization of milled almond shell (HMAS-L2) substrates proved effective for photoreforming, yielding significantly higher hydrogen productions than those obtained from substrates photodegradation and water splitting. As-prepared Cu/TiO2 showed efficient photocatalytic activity due to the facile in-situ reduction of Cu species. Conversely, Ni/TiO2 photocatalysts became active only after the reduction treatment, when partial formation of Ni0 species enhanced charge separation. The presence of reduced metals significantly improved photoactivity by decreasing charge recombination. The highest hydrogen productions reached were 2320 μmol·gcat−1· h−1 and 2440 μmol·gcat−1·h−1 with MC_5Ni-P25-r and HMAS-L2_5Cu/P25-r, respectively, surpassing previously reported literature values. The H2/CO2 molar ratios, with values close to the theoretical stoichiometric ratio (≈2), confirmed the predominant photoreforming pathway, while deviations indicated concurrent photodegradation and/or photoinduced water splitting. Tests with scavengers confirmed the effective photoreforming with MC and HMAS-L2 substrates, in contrast to milled almond shell and its derived solids.

This file contains the data of the manuscript Activating Agent-Free Synthesis of N,P-Co-Doped Porous Carbons from Lignocellulosic Waste for the Oxygen Reduction Reaction submitted for publication in Sustainability journal.

One recent trend in enzyme immobilization is the use of relatively simple immobilization techniques that produce ex novo solids containing the enzymes. Many of them may present some problems in the handling or during operation (by size and/or mechanical resistance), while bringing forth great improvements in the enzyme features. Other methods use metals, that can lead to unexpected effects. To solve this handling problems may be critical for the implementation of these biocatalysts. This is exemplified using different biocatalysts (enzymes immobilized on pre-existing macroporous supports or nanoparticles, crosslinking enzyme aggregates or enzyme-nanoflowers). After presenting the different immobilization techniques, and discussing the possible role of the metals, we shall discuss how the recovery and mechanical fragility issues can be solved. Recovering can be simplified just by using magnetic materials, while trapping in alginate or polyvinyl alcohol polymeric beads or immobilization in larger particles may solve both problems. Some additional advantages of this strategy are the improvement of enzyme stability, generation of enzyme nanoenvironments, which can permit the promotion of partition effects and produce enzyme stabilization in the presence of hydrophobic organic solvents or improve thermodynamic yields.