Designing highly active, durable, and nonprecious metal‐based bifunctional electrocatalysts for overall water electrolysis is of urgent scientific importance to realize the sustainable hydrogen production, which remains a grand challenge. Herein, an innovative approach is demonstrated to synthesize flower‐like 3D homogenous trimetallic Mn, Ni, Co phosphide catalysts directly on nickel foam via electrodeposition followed by plasma phosphidation. The electrochemical activity of the catalysts with varying Mn:Ni:Co ratios is assessed to identify the optimal composition, demonstrating that the equimolar trimetallic phosphide yields an outstanding HER catalytic performance with a current density of 10 mA cm−2 at an ultra‐low overpotential of ~14 mV, outperforming the best reported electrocatalysts. This is asserted by the DFT calculations, revealing strong interaction of the metals and the P atom, resulting in enhanced water activation and optimized GH* values for the HER process. Moreover, this optimal composition appreciably catalyzes the OER by exposing more intrinsic active species in‐situ formed on the catalyst surface during the OER. Therefore, the Mn1‐Ni1‐Co1‐P‐(O)/NF catalyst exhibits a decreased overpotential of ~289 mV at 10 mA cm−2. More importantly, the electrocatalyst sustains perfect durability up to 48 h at a current density of 10 mA cm−2 and continued 5000 cycling stability for both HER and OER. Meanwhile, the assembled MNC‐P/NF||MNC‐P/NF full water electrolyzer system attains an extremely low cell voltage of 1.48 V at 10 mA cm−2. Significantly, the robust stability of the overall system results in a remarkable current retention of ~96% after a continuous 50‐h run. Therefore, this study provides a facile design and a scalable construction of superb bifunctional ternary MNC‐phosphide electrocatalysts for efficient electrochemical energy production systems.
Herein, the ability to convert waste stainless steel (SS) 316L meshes into highly efficient and durable oxygen evolution reaction (OER) catalysts is demonstrated. The process involves surface treatment of previously anodized SS meshes in different gaseous atmospheres. The activity of the resulted electrocatalysts varies as-anodized SS annealed in oxygen (ASS-O2) > anodized SS annealed in hydrogen (ASS-H2) > anodized SS annealed in air (ASS-Air). The ASS-O2 showed an impressive low overpotential of 280 mV at the benchmark current density of 10 mA/cm2, which is 120 mV less than that of the as-received SS (SS-AR), and a low Tafel slope of 63 mV dec–1 in 1 M KOH. These findings have also been asserted by the estimated electrochemical active surface area, electrochemical impedance spectroscopy analysis, Mott–Schottky analysis, and the calculated turnover frequency, affirming the superiority of the ASS-O2 electrocatalyst over the ASS-H2 and ASS-Air counterparts. The high activity of the ASS-O2 electrocatalyst can be ascribed to the surface composition that is rich in Fe3+ and Ni2+ as revealed by the X-ray photoelectron spectroscopy analysis. The simple method of anodization and thermal annealing in O2 at moderate conditions (450 °C for 1 h) lead to the formation of a SS mesh-based OER electrocatalyst with activity exceeding that of the state-of-the-art IrO2/RuO2 and other complex modified SS catalysts. These results were also confirmed via density functional theory calculations, which unveiled the OER reaction mechanism and elucidated the d-band center in different SS samples with different oxygen content. The presence of oxygen moved the d-band center closer to the Fermi level in the case of ASS-O2, explaining its superior activity.
The search for materials with superior electrocatalytic performance has attracted attention during the past few years aiming to identify a convenient material that works at a low overpotential with long-term stability. Herein, we introduce an innovative technique to fabricate two-dimensional BCN heterostructure nanosheets with various Cu:BCN weight ratios. The fabricated composites showed unique electrocatalytic properties for hydrogen evolution reaction (HER). The morphology and structure of the electrocatalysts were characterized using field emission scanning electron microscopy, Raman, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy techniques. Remarkably, this study reveals the effect of electrochemical chronopotentiometry on facilitating the electrochemical exfoliation and hence enhancing the catalytic activity of the fabricated nanosheets. This effect was further confirmed via density functional theory (DFT) calculations, unveiling the effect of the formed oxide layer on the charge transfer process. The overpotential of the 0.125 Cu-BCN composite at a current density of -10 mA/cm 2 vs RHE is 50% lower than that of pristine BCN. These findings were also affirmed by the DFT calculations, which showed that incorporating copper on BCN has significantly reduced the G H* value of the HER and subsequently accelerates the kinetics of the reaction and the overall catalytic activity of the material.
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