General Synthesis of Sulfides Using Oxalates as Precursors and Their Applications for the Oxygen Evolution Reaction

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Abstract Developing low-cost and highly efficient transition-metal electrocatalysts for the oxygen evolution reaction (OER) is crucial for advancing sustainable clean energy technologies. Herein, using a N,N-dimethylacetamide-assisted gas-phase sulfidation strategy, we successfully construct a comprehensive library of monometallic (NiS2, CoS2, FeS2, CuS, MnS, CdS, and In2S3) and bimetallic sulfides including NiFe−S solid solutions and NiMn−S heterojunctions utilizing oxalates as precursors. Among the monometallic samples, NiS2 exhibited the optimal geometric apparent activity, requiring an overpotential of 402 mV to achieve 30 mA cm−2 in 1 M KOH with a Tafel slope of 95.0 mV dec−1. Conversely, the optimal bimetallic NiFe−S solid solution demanded an overpotential of only 377 mV to reach 30 mA cm−2 and exhibits an exceptionally small Tafel slope of 57.3 mV dec−1, outperforming a commercial IrO2 catalyst. Notably, the incorporation of iron into the NiS2 lattice triggered pronounced recrystallization, transforming the moderately rough surface into a dense, block-like architecture. Despite the reduced electrochemically active surface area, NiFe−S showed an intrinsic specific activity approximately three times higher than that of pristine NiS2. Furthermore, the unique dense architecture imparted robust resistance against deep bulk oxidation, ensuring outstanding durability over 72 h of continuous electrolysis. This work establishes a versatile and scalable oxalate-templated paradigm for designing highly crystalline multi-metallic sulfides with tunable compositions and morphologies.

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