Self-supported Co9S8-Ni3S2-CNTs/NF electrode with superwetting multistage micro-nano structure for efficient bifunctional overall water splitting

Phosphorus/sulfur co-doped heterogeneous NiCoPxSy nanoarrays boosting overall water splitting

In the large-scale implementation of renewable energy devices, the availability of stable and highly catalytic non-precious metal catalysts for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is crucial. Meanwhile, integrating bifunctional electrocatalysts simultaneously on both the anode and cathode still faces challenges. To address this, a stepped preparation strategy was adopted on a nickel foam (NF) substrate to synthesize P, S co-doped NiCoPxSy nanowire array catalysts. The prepared NiCoPxSy catalysts demonstrated a small Tafel slope of 72.5 mV dec-1 for HER and 72.3 mV dec-1 for OER by requiring only 37 mV (326 mV) overpotential to achieve a current density of 10 mA cm-2 (50 mA cm-2). Moreover, when assembled into an electrolytic cell in 1 M KOH, the NiCoPxSy catalysts achieved a low voltage of 1.55 V at 10 mA cm-2 current density and exhibited long-term stability. The outstanding electrocatalytic performance can be attributed to the influence of doped anions on the electronic states and distribution among different atoms, which thereby positively affected the electrocatalytic activity. This research provides an effective method for designing innovative catalysts and paving the way to produce clean energy.

Flower ball cathode assembled from Cu doped Co3S4/Ni3S2 ultrathin nanosheets in a photocatalytic fuel cell for efficient photoelectrochemical rifampicin purification and simultaneous electricity generation based on a CuO QDs/TiO2/WO3 photoanode

Herein, an efficient CuO QDs/TiO₂/WO₃ photoanode and a Cu doped Co₃S₄/Ni₃S₂ cathode were successfully synthesized. The optimized CuO QDs/TiO₂/WO₃ photoanode achieved a photocurrent density of 1.93 mA cm^-2 at 1.23 vs. RHE, which was 2.27 times that of a WO₃ photoanode. The CuO QDs/TiO₂/WO₃-buried junction silicon (BJS) photoanode was coupled with the Cu doped Co₃S₄/Ni₃S₂ cathode to construct a novel photocatalytic fuel cell (PFC) system. The as-established PFC system showed a high rifampicin (RFP) removal ratio of 93.4% after 90 min and maximum power output of 0.50 mW cm^-2. Quenching tests and EPR spectra demonstrated that ˙OH, ˙O₂^- and ¹O₂ were the main reactive oxygen species in the system. This work provides a possibility to construct a more efficient PFC system for environmental protection and energy recovery in the future.

A salt-baking 'recipe' of commercial nickel-molybdenum alloy foam for oxygen evolution catalysis in water splitting

Ni-based metal foam holds promise as an electrochemical water-splitting catalyst, due to its low cost, acceptable catalytic activity and superior stability. However, its catalytic activity must be improved before it can be used as an energy-saving catalyst. Here, a traditional Chinese recipe, salt-baking, was employed to surface engineering of nickel-molybdenum alloy (NiMo) foam. During salt-baking, a thin layer of FeOOH nano-flowers was assembled on the NiMo foam surface then the resultant NiMo-Fe catalytic material was evaluated for its ability to support oxygen evolution reaction (OER) activity. The NiMo-Fe foam catalyst generated an electric current density of 100 mA cm^-2 that required an overpotential of only 280 mV, thus demonstrating that its performance far exceeded that of the benchmark catalyst RuO₂ (375 mV). When employed as both the anode and cathode for use in alkaline water electrolysis, the NiMo-Fe foam generated a current density (j) output that was 3.5 times greater than that of NiMo. Thus, our proposed salt-baking method is a promising simple and environmentally friendly approach for surface engineering of metal foam for designing catalysts.