Electrodeposited rhenium–cobalt alloy with high activity for acidic hydrogen evolution reaction

Nitrided Rhodium Nanoclusters with Optimized Water Bonding and Splitting Effects for pH-Universal H2-Production

The nitridation of noble metals-based catalysts to further enhance their hydrogen evolution reaction (HER) kinetics in neutral and alkaline conditions would be an effective strategy for developing high-performance wide pH HER catalysts. Herein, a facile molten urea method is employed to construct the nitrided Rh nanoclusters (RhxN) supported on N-doped carbon (RhxN-NC). The uniformly distributed RhxN clusters exhibited optimized water bonding and splitting effects, therefore resulting in excellent pH-universal HER performance. The optimized RhxN-NC catalyst only requires 8, 12, and 109 mV overpotentials to reach the current density of 10 mA cm-2 in 0.5 M H2SO4, 1.0 M KOH, and 1.0 M PBS electrolytes, respectively. The spectroscopic characterizations and theoretical calculation further confirm the vital role of Rh-N moieties in RhxN clusters in improving the transfer of electrons and facilitating the generation of H2. This work not only provides a suitable nitridation method for noble metal species in mild conditions but also makes a breakthrough in synthesizing noble metal nitrides-based electrocatalysts to achieve an exceptional wide-pH HER performance and other catalysis.

Electrochemical tuning of a Cu3P/Ni2P hybrid for a promoted hydrogen evolution reaction

Developing novel and high performance electrocatalysts for use in hydrogen evolution reactions (HER) as substitutes for noble metal based electrocatalysts is imperative and, so far, has been a challenge. Herein, a self-supported Cu₃P/Ni₂P hybrid on nickel foam (Cu₃P/Ni₂P@NF) is prepared by a simple galvanic replacement reaction coupled with phosphorization. Subsequently, Cu₃P/Ni₂P@NF is modified by conducting cyclic voltammetry scans in 0.5 M H₂SO₄ solution. Interestingly, after electrochemical tuning, the as-prepared Cu₃P/Ni₂P@NF exhibits significantly enhanced HER activity. Particularly, the resultant Cu₃P/Ni₂P@NF catalyst after 4000 cycles exhibits superior catalytic activity and long-term stability for HER with an overpotential of only 67 mV at the current density of 10 mA cm^-2, and a low Tafel slope of 43.9 mV dec^-1. The improved HER performance is attributed to the increased intrinsic activity of the Cu₃P/Ni₂P@NF with its optimized crystal and electronic structure, as well as an increased number of accessible active sites due to surface dissolution and recrystallization induced by electrochemical modification.

Electrodeposition: An efficient method to fabricate self-supported electrodes for electrochemical energy conversion systems

The development of electrocatalysts for energy conversion systems is essential for alleviating environmental problems and producing useful energy sources as alternatives to fossil fuels. Improving the catalytic performance and stability of electrocatalysts is a major challenge in the development of energy conversion systems. Moreover, understanding their electrode structure is important for enhancing the energy efficiency. Recently, binder-free self-supported electrodes have been investigated because the seamless contact between the electrocatalyst and substrate minimizes the contact resistance as well as facilitates fast charge transfer at the catalyst/substrate interface and high catalyst utilization. Electrodeposition is an effective and facile method for fabricating self-supported electrodes in aqueous solutions under mild conditions. Facile fabrication without a polymer binder and controlability of the compositional and morphological properties of the electrocatalyst make electrodeposition methods suitable for enhancing the performance of energy conversion systems. Herein, we summarize recent research on self-supported electrodes fabricated by electrodeposition for energy conversion reactions, particularly focusing on cathodic reactions of electrolyzer system such as hydrogen evolution, electrochemical CO₂ reduction, and electrochemical N₂ reduction reactions. The deposition conditions, morphological and compositional properties, and catalytic performance of the electrocatalyst are reviewed. Finally, the prospective directions of electrocatalyst development for energy conversion systems are discussed.