In a search of alternates for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), out of various transition metal based electrocatalysts, layer double hydroxide (LDHs) based materials are attracted...

Water electrolysis plays a vital role in the generation of Hydrogen when compared to the other methods such as hydrolysis of metal hydride, steam reforming, coal gasification an oxidation of...

Vast attention from researchers is being given to the development of suitable oxygen evolution reaction (OER) electrocatalysts via water electrolysis. Being highly abundant, the use of transition-metal-based OER catalysts has been attractive more recently. Among the various transition-metal-based electrocatalysts, the use of layered double hydroxides (LDHs) has gained special attention from researchers owing to their high stability under OER conditions. In this work, we have reported the synthesis of trimetallic NiCoV-LDH via a simple wet-chemical method. The synthesized NiCoV-LDH possesses aggregated sheet-like structures and is screened for OER studies in alkaline medium. In the study of OER activity, the as-prepared catalyst demanded 280 mV overpotential and this was 42 mV less than the overpotential essential for pristine NiCo-LDH. Moreover, doping of a third metal into the NiCo-LDH system might lead to an increase in TOF values by almost three times. Apart from this, the electronic structural evaluation confirms that the doping of V 3+ into NiCo-LDH could synergistically favor the electron transfer among the metal ions, which in turn increases the activity of the prepared catalyst toward the OER.

Electrocatalytic water splitting has gained vast attention in recent decades for its role in catalyzing hydrogen production effectively as an alternative to fossil fuels. Moreover, the designing of highly efficient oxygen evolution reaction (OER) electrocatalysts across the universal pH conditions was more challengeable as in harsh anodic potentials, it questions the activity and stability of the concerned catalyst. Generally, geometrical engineering and electronic structural modulation of the catalyst can effectively boost the OER activity. Herein, a Co-doped RuO 2 nanorod material is developed and used as an OER electrocatalyst at different pH conditions. Co-RuO 2 exhibits a lower overpotential value of 238 mV in an alkaline environment (1 M KOH) with a Tafel slope value of 48 mV/dec. On the other hand, in acidic, neutral, and near-neutral environments, it required overpotentials of 328, 453, and 470 mV, respectively, to attain a 10 mA/cm 2 current density. It is observed that doping of Co into the RuO 2 could synergistically increase the active sites with the enhanced electrophilic nature of Ru 4+ to accelerate OER in all of the pH ranges. This study finds the applicability of earth-abundant-based metals like Co to be used in universal pH conditions with a simple doping technique. Further, it assured the stable nature in all pH electrolytes and needs to be further explored with other metals in the future.

Compositional-variation-induced CoFe-LDHs (with various Co:Fe ratio; LDH, layered double hydroxide) have been prepared via a simple wet-chemical method followed by the formation of 1D microfibers through electrospinning (ES) techniques. The as-synthesized 1D fiber with a Co/Fe ratio corresponding to a 0.5:1 microfiber (CoFe-LDH 0.5 fiber) showed the highest oxygen evolution reaction (OER) activity by demanding an overpotential value of 267 mV while the corresponding powder material demands an overpotential value of 312 mV at pH = 14. In addition, the neutral OER activity of the catalysts was also verified in 0.2 M phosphate buffer solution (PBS), and the same CoFe-LDH 0.5 fiber demands a lower overpotential value of 300 mV while the CoFe-LDH 1 fiber and CoFe-LDH 1.5 fiber demand 320 and 340 mV overpotential, respectively. Hence, we have obtained the interesting result that the incorporated 1D fibrous material with lower cobalt content showed a higher activity than the other fibrous materials. A magnetic study shows that the presence of cobalt ions with a lower concentration ensures the higher ferromagnetic (FM) interaction among the cobalt ions which in turn polarize the overall electronic spin of the hydroxide entity. The polarization of the electronic spin results in lowering the energy barrier by omitting the spin inversion barrier.

Energy scarcity and environmental pollution are major threats to the long-term viability of the modern civilization. Electrocatalytic water splitting is a crucial technology for environmentally friendly and long-lasting energy storage...

To generate green hydrogen by water electrolysis, it is vital to develop highly efficient electrocatalysts for the oxygen evolution reaction (OER). The utilization of various 3d transition metal-based layered double hydroxides (LDHs), especially NiFe− LDH, has gained vast attention for OER under alkaline conditions. However, the lack of a proper electronic structure of the NiFe− LDH and low stability under high-pH conditions limit its largescale application. To overcome these difficulties, in this study, we constructed an Sn-doped NiFe−LDH material using a simple wetchemical method. The doping of Sn will synergistically increase the active surface sites of NiFe−LDH. The highly active NiFe−LDH Sn 0 . 015(M) shows excellent OER activity by requiring an overpotential of 250 mV to drive 10 mA/cm 2 current density, whereas the bare NiFe−LDH required an overpotential of 295 mV at the same current density. Also, NiFe−LDH Sn 0 . 015(M) shows excellent long-term stability for 50 h in 1 M KOH and also exhibits a higher TOF value of 0.495 s −1 , which is almost five times higher than that of bare NiFe−LDH. This study highlights Sn doping as an effective strategy for the development of low-cost, effective, stable, self-supported electrocatalysts with a high current density for improved OER and other catalytic applications in the near future.

Rational design and fabrication of electrocatalysts with outstanding performances and long-term durabilities are highly challenging for overall water-splitting reactions. Herein, interfacially engineered CoS@NiV-LDH heterostructures are fabricated by a simple top-down approach and used as bifunctional electrocatalysts for overall water splitting. Experimental results proved that the creation of an interface between pristine CoS and NiV-LDH can optimize the electronic structure of the active sites by transferring electrons from the NiV-LDH site to CoS, which boosts the formation of the NiOOH active phase, enhancing the catalytic performance in a 1 M KOH solution. While coupled with the heterostructure CoS@NiV-LDH as the anode and cathode, it demands a cell voltage of just 1.57 V to attain a current density of 10 mA cm–2 with remarkable stability for 70 h. Density functional theory (DFT) calculations reveal improved catalytic activity toward the oxygen evolution reaction (OER) for CoS@NiV-LDH with a lower energy barrier originating from the charge transfer-induced synergistic mechanism at the CoS and NiV-LDH interface. Moreover, the observed downshift of the d-band center for the CoS@NiV-LDH heterostructure explains their enhanced performance toward the hydrogen evolution reaction (HER), facilitating the H* adsorption/desorption process.