An important obstacle to long-term hydrogen sustainability is the lack of efficient and stable non-noble-metal catalysts for hydrogen generation through water electrolysis. Cobalt phosphides have emerged as earth-abundant catalysts for the hydrogen evolution reaction (HER), and its activity can be augmented by admixing synergistic elements to produce heteroatom-doped catalysts. Herein, we report an integrated computational and experimental study leading to the synthesis of Co1–xMnxP nanocrystals (NCs) displaying superior activity and stability for the alkaline HER compared to the benchmark Pt/C catalyst at higher current densities (j ≥ −35 mA/cm2). Density functional theory calculations predicted that Mn doping modulates the hydrogen adsorption energies (ΔGH) of orthorhombic CoP toward thermoneutral values. Accordingly, a series of Co1–xMnxP NCs (x = 0.038–0.169) with control over structure, morphology, and composition was produced via colloidal synthesis. Physical characterization of Co1–xMnxP NCs revealed an orthorhombic structure, pseudospherical morphology, and average diameters of ∼5.7–10.2 nm. The incorporation of Mn caused significant modulation of the electronic structure prompting a decrease in Co(2p) and P(2p) binding energies, suggesting an increase in electron density on both surface sites. Among NCs investigated, Co0.909Mn0.091P composition displayed the highest HER activity with an overpotential (η–10) of 136.29 mV at j = −10 mA/cm2, consistent with composition-dependent ΔGH studies. With a Tafel slope of 65.77 mV/dec, Co0.909Mn0.091P NCs showed similar kinetics to the Pt/C catalyst (62.31 mV/dec), indicating the Volmer-Heyrovsky HER mechanism. The highest-performing Co0.909Mn0.091P NCs showed a prominent increase in electrochemically active surface area and significantly lower charge transfer resistance compared to parent CoP NCs. The Co0.909Mn0.091P NCs showed exceptional stability in alkaline media compared to CoP NCs and commercial Pt/C catalysts. Co0.923Mn0.077P, Co0.909Mn0.091P, and Co0.831Mn0.169P compositions displayed superior HER activity and stability compared to monometallic CoP NCs suggesting that dopant-induced compositional and surface modification is an effective strategy for designing high-efficiency, durable nanostructures for numerous heterogeneous (electro)catalytic studies.
Alam et al. (2026) studied this question.