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Noncentrosymmetric (NCS) silicon phosphides have recently shown promise as nonlinear optical materials due to the balance of strong second harmonic generation (SHG) activity and large laser damage threshold (LDT) values. While arsenides of electropositive metals, such as Ba, Mg, Zn, and Cd were explored, no NLO properties for transition metal tetrel arsenides have yet been reported. IrSi 3 As 3 is a novel compound, isostructural to IrSi 3 P 3 , which allows a direct investigation on the impact of the heavier pnictogen on structural and optical properties. The direct bandgap is reduced from 1.8 eV for IrSi 3 P 3 to 1.55 eV for IrSi 3 As 3 . Unlike many NLO chalcogenides, IrSi 3 As 3 has a small bandgap without compromising the balance between SHG signal and high LDT values. IrSi 3 As 3 was found to outperform both its phosphide analogue IrSi 3 P 3 , as well as the state-of-the-art infrared SHG standard AgGaS 2 (AGS) in SHG activity and the LDT. 

A facile and universal route for synthesizing transition metal borides has been developed by reaction of boron triiodide (BI 3 ) with elemental transition metals. This method employs relatively low synthesis temperatures to afford single-phase samples of various binary and ternary metal borides, such as Fe 2 B, Co 2 B, Ni 3 B, TiB 2 , VB 2 , CrB 2 , and Ni 2 CoB. This synthesis protocol can be utilized for the topotactic transformation of metal shapes into their respective borides, as exemplified by transformation of Ni foam to Ni 3 B foam. In situ powder X-ray diffraction studies of the Ni–BI 3 system showed that the crystalline nickel borides, Ni 4 B 3 and Ni 2 B, start to form at temperatures as low as 700 K and 877 K, respectively, which is significantly lower than the typical synthesis temperatures required to produce these borides. Ni 3 B synthesized by this method was tested as a supporting material for oxygen evolution reaction (OER) in acidic media. Composite electrocatalysts of IrO 2 /Ni 3 B with only 50% of IrO 2 exhibit current densities and stability similar to pure IrO 2 at mass loadings lower than 0.5 mg cm −2 , indicating Ni 3 B could be a promising supporting material for acidic OER. 

To combat the global problem of carbon dioxide emissions, hydrogen is the desired energy vector for the transition to environmentally benign fuel cell power. Water electrolysis (WE) is the major technology for sustainable hydrogen production. Despite the use of renewable solar and wind power as sources of electricity, one of the main barriers for the widespread implementation of WE is the scarcity and high cost of platinum group metals (pgms) that are used to catalyse the cathodic hydrogen evolution reaction (HER) and the anodic oxygen evolution reaction (OER). Hence, the critical pgm-based catalysts must be replaced with more sustainable alternatives for WE technologies to become commercially viable. This critical review describes the state-of-the-art pgm-free materials used in the WE application, with a major focus on phosphides and borides. Several emerging classes of HER and OER catalysts are reviewed and detailed structure‐property correlations are comprehensively summarised. The influence of the crystallographic and electronic structures, morphology and bulk and surface chemistry of the catalysts on the activity towards OER and HER is discussed.