Dino Villagrán

Nanostructured photocatalytic and PEC systems can simultaneously remediate diverse wastewater contaminants while generating green hydrogen. This review evaluates these dual-function strategies and highlights gaps in real wastewater validation.

Advancing metal-free electrocatalysts for hydrogen and oxygen evolution reactions (HER/OER) across acidic and alkaline media requires coordinated control of intermediate binding thermodynamics, interfacial charge delivery, and near-electrode transport dynamics. Here, we design amide-linked benzene–triazine covalent organic frameworks (BTA/TzTA-Hz COFs) and integrate them with carbon nanotubes (CNTs) to form COF–CNT junctions that establish a built-in interfacial electric field. Density functional theory (DFT) and electrostatic potential maps indicate complementary active motifs, with benzene-proximal fragments associated with HER and triazine-proximal motifs associated with OER. CNT integration shifts the contact-potential difference by ≈0.20 V, while operando electrochemical impedance spectroscopy suggests partially separable high-frequency junction-charging and lower-frequency Faradaic/transport responses. A 300 mT static magnetic field lowers the HER and OER overpotentials by tens of millivolts. Under anodic bias, the effective interfacial charging capacitance increases, and Mott–Schottky analysis shows an apparent ∼0.15 V flat-band shift with an essentially unchanged slope. Together, these observations are consistent with field-perturbed interfacial charging and altered bias partitioning. Field-dependent impedance and bubble imaging are consistent with magnetohydrodynamic convection that promotes bubble detachment and near-electrode mass transport for both half-reactions, and they reveal an OER-specific high-frequency perturbation under anodic bias. Under field, the heterostructure reaches an OER onset overpotential of ∼261 mV and requires an overpotential of 366 mV at 10 mA cm–2 in alkaline electrolyte. These results illustrate how reticular-framework chemistry, junction engineering, and both built-in and applied fields can program reactivity through interfacial electrostatics and near-electrode transport in organic-framework electrocatalysts.

Here we present a one-step synthesis of bimetallic cobalt ruthenium sulfide on Vulcan XC-72R carbon (C-CoₓRuS) for electrochemical water splitting, which was coupled with CoTcPP (cobalt 5,10,15,20-tetrakis(4-carboxyphenyl) porphyrin) for improved Oxygen Evolution Reaction (OER) electrocatalysis. Electrochemical analyses reveal that increasing cobalt content enhances the maximum current density by 8x for HER and 3x for OER. The optimized C-Co4RuS catalyst demonstrates bifunctional activity with an HER overpotential of -75 mV (vs. RHE) at 10 mA cm^-2 and a Tafel slope of 75 mV dec^-1 for HER (Volmer-Heyrovsky mechanism) and an overpotential of 251 mV (vs. RHE) at 10 mA cm^-2 with a Tafel slope of 95 mV dec^-1 for OER. The addition of cobalt to the ruthenium sulfide material facilitates charge transfer and improves active site accessibility according to Electrochemical Impedance Spectroscopy (EIS) and Electrochemical Active Surface Area (ECSA) data. Upon CoTcPP compositing the OER overpotential and Tafel plot decrease to 204 mV (vs. RHE) and 79 mV dec^-1 further improving its catalytic activity. These findings position C-Co_xRuS/CoTcPP as an efficient, bifunctional electrocatalyst, providing a viable alternative to common electrocatalysts for water splitting in sustainable energy applications.

We report the synthesis, characterization, and electrochemical analysis of a heterogeneous composite featuring cobalt(II) meso-tetrakis(4-carboxyphenyl)porphyrin (CoTcPP, 1) and zinc 2,3,6,7,10,11-hexahydroxytriphenylene-based (ZnHHTP, 2) metal organic framework (MOF), denoted CoTcPP@ZnHHTP (3). The resulting composite 3 has cobalt porphyrin as the electroactive site, while the ZnHHTP substrate serves as a highly conductive support providing adsorption sites for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), such as H_⁺ and OH^-. FT-IR spectra of the composite display characteristic bands from both precursors with shifts in aromatic C=C and carboxylate stretching modes and perturbation of the O-H region, consistent with secondary interactions between CoTcPP and the ZnHHTP framework. The XRD reveals that 3 has both crystalline diffraction peaks attributed to the ZnHHTP phase, and a new peak assigned to the cobalt porphyrin. Additionally, the EDX of 2 shows the absence of cobalt, while composite 3 displays a clear cobalt signal, indicating incorporation of CoTcPP onto the ZnHHTP. Composite 3 demonstrates bifunctional electrocatalytic activity, with overpotentials at j₁₀ mA cm^-2 (η₁₀) of 340 mV for the OER and 362 mV for the HER. Notably, the HER η₁₀ decreases to 146 mV when the composite is employed as both the anode and cathode. The material also shows a Tafel slope of 55 mV dec^-1 for OER, comparable to benchmark catalysts. It is stable for over 14 h, with a Faradaic efficiency of 98%. The composite achieves TOF of 1.8 s^-1 for OER and 6.2 s^-1 for HER, along with corresponding TON of 90,000 and 314,000, respectively.

Electrografted CoTPP and H₂TPP on GCEs enable efficient OER and HER. LSV shows enhanced catalytic activity of modified electrodes compared to bare GCE.