Improving NiFe Electrocatalysts through Fluorination-Driven Rearrangements for Neutral Water Electrolysis.

Neutral electrolysis to produce hydrogen is prime challenging owing to the sluggish kinetics of water dissociation for the electrochemical reduction of water to molecular hydrogen. An ion-enriched electrode/electrolyte interface for electrocatalytic reactions can efficiently obtain a stable electrolysis system. Herein, we found that interfacial accumulated fluoride ions and the anchored Pt single atoms/nanoparticles in catalysts can improve hydrogen evolution reaction (HER) activity of NiFe-based hydroxide catalysts, prolonging the operating stability at high current density in neutral conditions. NiFe hydroxide electrode obtains an outstanding performance of 1000 mA cm-2 at low overpotential of 218 mV with 1000 h operation at 100 mA cm-2. Electrochemical experiments and theoretical calculations have demonstrated that the interfacial fluoride contributes to promote the adsorption of Pt to proton for sustaining a large current density at low potential, while the Pt single atoms/nanoparticles provide H adsorption sites. The synergy effect of F and Pt species promotes the formation of Pt─H and F─H bonds, which accelerate the adsorption and dissociation process of H2O and promote the HER reaction with a long-term durability in neutral conditions.

Enhanced Charge Carrier Dynamics on Sb2 Se3 Photocathodes for Efficient Photoelectrochemical Nitrate Reduction to Ammonia.

Ammonia (NH3 ) is recognized as a transportable carrier for renewable energy fuels. Photoelectrochemical nitrate reduction reaction (PEC NO3 RR) offers a sustainable solution for nitrate-rich wastewater treatment by directly converting solar energy to ammonia. In this study, we demonstrate the highly selective PEC ammonia production from NO3 RR by constructing a CoCu/TiO2 /Sb2 Se3 photocathode. The constructed CoCu/TiO2 /Sb2 Se3 photocathode achieves an ammonia Faraday efficiency (FE) of 88.01 % at -0.2 VRHE and an ammonia yield as high as 15.91 µmol h-1 cm-2 at -0.3 VRHE with an excellent onset potential of 0.43 VRHE . Dynamics experiments and theoretical calculations have demonstrated that the CoCu/TiO2 /Sb2 Se3 photocathode possesses high light absorption capacity, excellent carrier transfer capability, and high charge separation and transfer efficiencies. The photocathode can effectively adsorb the reactant NO3 - and intermediate, and the CoCu co-catalyst increases the maximum Gibbs free energy difference between NO3 RR and HER. Meanwhile, the Co species enhances the spin density of Cu, and increases the density of states near the Fermi level in pdos, which results in a high PEC NO3 RR activity on CoCu/TiO2 /Sb2 Se3 . This work provides a new avenue for the feasibility of efficient PEC ammonia synthesis from nitrate-rich wastewater.

Unbiased photoelectrochemical H2O2 coupled to H2 production via dual Sb2S3-based photoelectrodes with ultralow onset potential.

The productions of hydrogen peroxide (H2O2) and hydrogen (H2) in a photoelectrochemical (PEC) water splitting cell suffer from an onset potential that limits solar conversion efficiencies. The formation of H2O2 through two-electron PEC water oxidation reaction competes with four-electron oxidation evolution reaction. Herein, we developed the surface selenium doped antimony trisulfide photoelectrode with the integrated ruthenium cocatalyst (Ru/Sb2(S,Se)3) to achieve the low onset potential and high Faraday efficiency (FE) for selective H2O2 production. The photoanode exhibits an average FE of 85% in the potential range of 0.4-1.6 VRHE and the H2O2 yield of 1.01 µmol cm-2 min-1 at 1.6 VRHE, especially at low potentials of 0.1-0.55 VRHE with 80.4% FE. Impressively, an unassisted PEC system that employs light and electrolyte was constructed to simultaneously produce H2O2 and H2 production on both Ru/Sb2(S,Se)3 photoanode and the Pt/TiO2/Sb2S3 photocathode. The integrated system enables the average PEC H2O2 production rate of 0.637 µmol cm-2 min-1 without applying any addition bias. This is the first demonstration that Sb2S3-based photoelectrodes exhibit H2O2/H2 two-side production with a strict key factor of the system, which represents its powerful platform to achieve high efficiency and productivity and the feasibility to facilitate value-added products in neutral conditions.

Enhanced Charge-carrier Dynamics and Efficient Photoelectrochemical Nitrate-to-ammonia Conversion on Antimony Sulfide-based Photocathodes.

The photoelectrochemical reduction of nitrate to ammonia (PEC NO3RR) has emerged as a promising pathway for facilitating the natural nitrogen cycle. The PEC NO3RR can lower the reduction potential needed for ammonia synthesis through photogenerated voltage, showcasing the significant potential for merging abundant solar energy with sustainable nitrogen fixation. However, it is influenced by the selective photocathodes with poor carrier kinetics, low catalytic selectivity, and ammonia yields. There are few reports on suitable photoelectrodes owning efficient charge transport on PEC NO3RR at low overpotentials. Herein, we rationally constructed the CuSn alloy co-catalysts on the antimony sulfides with a highly selective PEC ammonia and an ultra-low onset potential (0.62 VRHE). CuSn/TiO2/Sb2S3 achieved an ammonia faradic efficiency of 97.82% at a low applied potential of 0.4 VRHE, and an ammonia yield of 16.96 µmol h-1 cm-2 at 0 VRHE under one sun illumination. Dynamics experiments and theoretical calculations have demonstrated that CuSn/TiO2/Sb2S3 has an enhanced charge separation and transfer efficiency, facilitating photogenerated electrons to participate in PEC NO3RR quickly. Meanwhile, moderate NO2* adsorption on this photocathode optimizes the catalytic activity and increases the NH4+ yield. This work opens an avenue for designing sulfide-based photocathodes for the efficient route of solar-to-ammonia conversion.