Lee, Yeongbin Choi, Seyoung Jang, Seohyeon Cho, Byeong-Gwan Jeong, Beomgyun Kim, Yongsam Park, Yoonsu Jeong, Wooseok Hwang, Yun Jae Lee, Hyeonseok An, Boeun Jeong, Heesoo Kim, Gyuhyeon Qi, Dong-Chen Jang, Jong Hyun Nam, Inho Ha, Don-Hyung 2025-12-22T07:30:13Z 2025-12-22T07:30:13Z 2025-12-19 2026-01 2050-7488 https://pubs.kist.re.kr/handle/201004/153833 Nickel phosphides have emerged as promising earth-abundant catalysts for the hydrogen evolution reaction (HER), yet most studies have focused on Ni-rich phases (e.g., Ni2P, Ni5P4), where catalytic activity is commonly attributed to metallic Ni surface sites. In contrast, the catalytic potential of phosphorus-rich phases has remained largely unexplored due to synthetic challenges that have hindered access to phase-pure compositions. Here, we report the colloidal synthesis of phase-controlled Ni–P nanocrystals, granting access to four distinct phases (Ni12P5, Ni2P, Ni5P4, NiP2) and overcoming long-standing barriers such as phosphorus volatility and biphasic formation. This synthetic platform enables a direct and systematic comparison across the compositional gradient and reveals a fundamentally distinct HER mechanism at the P-rich end: hydrogen adsorption and evolution proceed preferentially on surface phosphorus atoms, rather than on Ni hollow or bridge sites as in conventional Ni-rich phosphides. Electrochemical analysis and density functional theory (DFT) calculations show that NiP2 exhibits superior HER performance compared to its Ni-rich analogues, despite having a lower electrochemically active surface area. This P-site-driven reactivity uncovers a previously unrecognized catalytic regime and challenges the prevailing Ni-centric model in transition metal phosphide catalysis. Our findings demonstrate that tuning the stoichiometry toward phosphorus-rich compositions not only alters the surface electronic structure but also redefines the identity of the active site. This work positions NiP2 as a prototype for anion-driven HER catalysis and introduces a new conceptual framework for designing non-precious electrocatalysts that exploit metalloid-active centers. English Royal Society of Chemistry Colloidal phase control of Ni–P nanocrystals reveals a P-site hydrogen evolution reaction mechanism distinct from Ni-rich analogues Article 10.1039/d5ta06219e 1 Journal of Materials Chemistry A, v.14, no.2, pp.988 - 1000 Journal of Materials Chemistry A 14 2 988 1000 N scie scopus 001623014300001 2-s2.0-105022854201 Chemistry, Physical Energy & Fuels Materials Science, Multidisciplinary Chemistry Energy & Fuels Materials Science Article TOTAL-ENERGY CALCULATIONS MOLYBDENUM PHOSPHIDE HIGH-PERFORMANCE ELECTROCATALYST NANOPARTICLES PHOTOELECTRON SPECTROSCOPY NANOSTRUCTURED NICKEL PHOSPHIDE PHOSPHORUS ABSORPTION